USGS Publications Warehouse

Evaluation of nutrient, alkalinity, and acid-neutralizing capacity stabilities in water samples analyzed by the U.S. Geological Survey National Water Quality Laboratory, 2023–24

Struzeski, Tedmund M.; Wetherbee, Gregory A.; Morrison, Jonathan — Mon, 8 Jun 2026 18:27:12

The U.S. Geological Survey evaluated the stability of water-sample chemical analysis of nutrient, alkalinity, and acid-neutralizing capacity constituents with respect to the duration between sample collection and laboratory analysis, also known as the sample holding time. A study began in the spring of 2023 to evaluate the sample stability, between 2 and 180 days after sample collection, of the chemical properties and chemical constituents of alkalinity as calcium carbonate, filtered; acid-neutralizing capacity as calcium carbonate, unfiltered; total ammonia as nitrogen, filtered; total ammonia plus organic nitrogen as nitrogen, filtered and unfiltered; nitrite as nitrogen, filtered; nitrate plus nitrite as nitrogen, filtered; total nitrogen, filtered and unfiltered; orthophosphate as phosphorous, filtered; and total phosphorus as phosphorus (filtered and unfiltered) in water. Both surface water and groundwater matrices were represented.

Sample instability varied by observed property and matrix; therefore, providing general guidance for sample holding time is not possible based on matrices alone. No correlations between field measurements of sample characteristics and sample instability were observed. Although observations for some properties indicate sample stability that exceeds the recognized U.S. Geological Survey National Water Quality Laboratory method holding times, this is not necessarily the case for matrices and seasonal characteristics that were not investigated.

Based on the limited number of six sample sources used in this study, some patterns emerge for the 12 observed properties studied. Five observed properties generally indicate stability for as many as 180 days after sampling (total nitrogen as nitrogen, both filtered and unfiltered; orthophosphate as phosphorus, filtered; and phosphorus as phosphorus, both filtered and unfiltered). Other observed properties indicate stability for as many as 180 days for some matrices, but not for others. Finally, some observed properties indicate instability well before 180 days.

Spatial and temporal trends of mercury in fish from Duck Valley Reservation Reservoirs, southwestern Idaho and northern Nevada, 2007–24

Murray, Erin — Mon, 8 Jun 2026 16:38:33

The Shoshone-Paiute (Sho-Pai) Tribes of the Duck Valley Reservation, Nevada, manage reservoirs that support commercial and recreational activities, including robust Oncorhynchus mykiss (rainbow trout) fisheries that attract anglers year-round. Reservoirs are common environments for methylation and bioaccumulation of mercury, which is a potent neurotoxin when elevated levels are consumed. The U.S. Geological Survey (USGS), in cooperation with the Sho-Pai Tribes, measured total mercury concentrations in the muscle tissue of rainbow trout from three Reservation reservoirs in Idaho and Nevada in 2007, 2009, 2013, and 2024. This report highlights spatial and temporal trends of mercury concentrations in rainbow trout in the Duck Valley Reservation reservoirs from 2007 through 2024, and presents limited data on other commonly consumed species, specifically Perca flavescens (yellow perch), Micropterus dolomieu (smallmouth bass), and Micropterus salmoides (largemouth bass). Mercury data are also presented for nearby sites and lower trophic level species. In 2024, two fish sampling methods were used and compared: biopsy muscle plugs and muscle fillets. Results show good agreement between mercury concentrations of biopsy and fillet muscle samples taken from the same fish, with most sample pairs differing by less than 20 percent, though biopsied fish had an unexpectedly high mortality rate. Mercury concentrations increased in Sheep Creek Reservoir during the study period, but no significant trend was observed in Mountain View Reservoir or Lake Billy Shaw. Only 1 rainbow trout out of 160 sampled in the Reservation reservoirs during the study period exceeded the U.S. Environmental Protection Agency’s recommended methylmercury criterion of 0.3 milligram per kilogram of wet weight (mg/kg ww). Largemouth bass, smallmouth bass, and yellow perch had higher mercury concentrations than rainbow trout and may pose a greater risk to consumers. Mercury concentrations in largemouth bass exceeded 0.3 mg/kg ww, although only two fish were sampled, both from Sheep Creek Reservoir. Fish consumption advisories on Tribal lands are determined by the Tribes, and these results may help Sho-Pai managers determine the mercury exposure risk to Tribal members and visiting anglers.

Magnitude and frequency of peak and low flows in the Elkhorn River Basin, Nebraska, 1881–2022

Strauch, Kellan R.; Dietsch, Benjamin — Mon, 8 Jun 2026 17:31:38

Flood-frequency analysis is based on records of annual maximum instantaneous flows observed at long-term streamgages with 10 years or more of operation. Since the last flood-frequency analysis in Nebraska, an additional 30 years of annual peak-flow data have become available, and new flood-frequency analysis techniques have been developed. Moreover, the Elkhorn River Basin in north-central and eastern Nebraska has experienced two of the three highest magnitude floods on record in 2010 and 2019. The U.S. Geological Survey, in cooperation with the Nebraska Department of Transportation, analyzed flow frequency at streamgages in the Elkhorn River Basin in Nebraska.

Flow data from the U.S. Geological Survey and the Nebraska Department of Water, Energy, and Environment annual hydrographic reports were utilized to analyze peak flows. The Peak flow FreQuency (PeakFQ) software was used to perform a flood-frequency and nonstationarity analysis on the selected streamgages in the Elkhorn River Basin in Nebraska. Results of the peak-flow nonstationarity analysis indicate that, of the 23 streamgages analyzed for peak-flow frequency, 4 showed trends that were likely increasing for annual peak flows, whereas 3 indicated trends that were somewhat likely to be increasing. For 11 streamgages, the trend was categorized as about as likely as not, meaning there is less than a 70-percent chance of the trend being either upward or downward. Additionally, 2 streamgages exhibited trends that were somewhat likely to be decreasing, and 3 streamgages showed trends that were likely decreasing.

Low-flow streamflows and nonstationarity in the Elkhorn River Basin were analyzed for low flow periods representing the 1-day, 7-day, and 30-day flows at 21 streamgages using the Hydrologic Toolbox software. Spatially, the nonstationarity analysis results indicated likely increasing or somewhat increasing trend likelihoods for the 1-day, 7-day, and 30-day low flows for many of the Elkhorn streamgages downstream from the Elkhorn River at Ewing, Nebr., streamgage (U.S. Geological Survey station 06797500) and on eastern tributaries during the period of record.

Open water control of invasive mussels using benthic mats—Part 1, short-term infusion of carbon dioxide under a mat

Mon, 8 Jun 2026 16:46:20

This study compared the efficacy of a benthic mat alone with carbon dioxide infusion under a mat for killing Dreissena polymorpha (Pallas, 1771) (zebra mussel). Three sites were selected in Loon Lake, Sleeping Bear Dunes National Lakeshore, Benzie County, Michigan, for replication of reference, benthic mat, and carbon dioxide mat treatments. Within a site, three 4-meter (m) x 4-m plots were delineated for each treatment and a reference. Pretreatment samples were collected to estimate zebra mussel density and macroinvertebrate community composition in reference plots. Zebra mussels (about 360) from outside of the treatment plots were caged and placed in the plots before treatment. Benthic mats (4.25 m x 4.25 m; polyethylene with a vinyl coating) were anchored on the lake bottom with sandbags and weights. Carbon dioxide was infused under a mat of the same material to a maximum of 200 milligrams per liter (mg/L; pH=6.13) every 2–4 hours, for about 12 hours. Benthic and carbon dioxide mats were deployed for 5 days. One day after mat removal, we assessed mortality of resident and sentinel caged zebra mussels and macroinvertebrate community abundance and diversity in each plot. Average pH (as a proxy for carbon dioxide) under the carbon dioxide mats was between 6.38 and 6.80, equivalent to 170.5 and 103.0 mg/L carbon dioxide, respectively. In the posttreatment survey, few zebra mussels were observed in the benthic mat and carbon dioxide treatment plots compared to the reference plots; survival was lowest in the carbon dioxide plots. Mortality of sentinel caged mussels was greater than 80 percent in carbon dioxide treatments compared to mean mortalities of 20.6 percent and 12.7 percent in the benthic mat and reference plots, respectively. Macroinvertebrate community total abundance was lower in both mat treatments compared to reference plots, but diversity was comparable among all treatments. Our study demonstrated that carbon dioxide treatment near 200 mg/L could produce greater than 80-percent mortality of zebra mussels within 5 days. Refinement of the carbon dioxide mat and delivery system could increase spatial coverage of the treatment and broaden its use to other habitats.

Remotely sensed surface water storage shows distinct patterns from SWAT-simulated data

Tue, 9 Jun 2026 16:29:25

Quantifying and projecting the downstream benefits of water stored in lakes and wetlands (SW_storage) requires watershed hydrologic models, which often parameterize surface water storage in topographic depressions using static digital elevation model (DEM) data. Calibration and validation of modeled SW_storage dynamics using external data sets is uncommon, particularly across major river basins, with model calibration typically focused on observed discharge. Here, we develop and assess a novel remote sensing-based (RS) SW_storage data set (Sentinel-1 and Sentinel-2) for verifying simulated SW_storage estimates from a Soil and Water Assessment Tool (SWAT) model of the Upper Mississippi River Basin (UMRB; ∼440,000 km²). Our results suggest that static DEM-based parameterization as well as model calibration based solely on discharge do not adequately capture spatial and temporal SW_storage dynamics in the UMRB. Mean SW_storage as estimated by SWAT was 74% ± 122% (mean ± standard deviation) higher than RS SW_storage, where SW_storage in SWAT was underestimated in wetland-rich subbasins and overestimated in agricultural, tile-drained subbasins. Time series of SWAT SW_storage and RS SW_storage were positively correlated in only 38.8% of subbasins. As RS SW_storage is also vulnerable to error, storage estimates were compared to bathymetric data in select small wetlands. While uncertainty remains in the conversion from extent to storage for RS SW_storage, the method and data set presented here are a promising option for improved parameterization and calibration of SW_storage processes in SWAT and other process-based hydrologic models. Further consideration of these storage processes can potentially improve the accuracy of simulated streamflow in wetland-rich model domains.

PFAS remediation in a bioelectrochemical system inoculated with the west branch consortium (WBC-2)

Yang, Haoran; Lorah, Michelle; Bender, Kelly; Xia, Chunjie; Sun, Jiasi; Liu, Jia — Tue, 9 Jun 2026 15:12:13

Groundwater contamination by per- and polyfluoroalkyl substances (PFAS) poses a persistent environmental and public health concern. This study evaluates a two-chambered bioelectrochemical system (BES) inoculated with the West Branch Consortium (WBC-2) for PFAS remediation. Under an applied cathodic potential of −450 mV (versus Ag/AgCl), the BES with active WBC-2 achieved >99.0% perfluorooctanesulfonic acid (PFOS) removal within 21 days in deionized water with culture medium and > 98.9% removal of PFOS, perfluorooctanoic acid (PFOA), perfluorohexanoic acid (PFHxA), and perfluorohexanesulfonic acid (PFHxS) in contaminated groundwater after 102 days. Intermediate formation (e.g., PFOA, 6:2 fluorotelomer sulfonate (6:2 FTS), perfluoropropionic acid (PFPrA), perfluorobutanoic acid (PFBA)) and background-corrected fluoride release were consistent with PFOS transformation under anaerobic reducing conditions potentially involving defluorination. Following repeated PFOS spikes (100 μg/L on Days 0, 50, and 399), PFOA, PFPrA, and PFBA accumulated over 664 days. Despite being the dominant accumulated compound, PFOA accounted for <1.8% of the total spiked PFOS mass. Minimal PFOS transformation occurred in controls without active WBC-2, highlighting the importance of microbial metabolism. Biofilm analysis revealed dense colonization of rod-shaped bacteria on carbon fiber brushes. Enrichment of Bacillus, Agrobacterium, and other low-abundance taxa suggests selective adaptation to BES and PFAS conditions. These findings highlight BES driven by electrochemically stimulated microbial activity as a promising strategy for PFAS remediation.

Arizona Water Science Center activities at Lees Ferry, Arizona

Cooney, Kathryn Anne — Mon, 8 Jun 2026 17:29:10

Introduction

In 1921, the U.S. Geological Survey (USGS) established a streamgage on the Colorado River at Lees Ferry, Arizona, to monitor the river’s flow and level as it enters Grand Canyon. The following year, the seven States encompassing the Colorado River Basin (Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming) negotiated the 1922 Colorado River Compact to regulate distribution of the river’s waters between them. The compact divided the basin into two regions—the Upper Basin and the Lower Basin—and established the dividing point between them about one mile downstream from Lees Ferry, just below the confluence of the Colorado and Paria Rivers.

The Colorado River at Lees Ferry streamgage (USGS station 09380000) is one of the most important streamgages in the United States because it is used to measure how much water passes from the Upper Basin to the Lower Basin through Glen Canyon Dam. The dam, constructed between 1956 and 1966, generates hydropower and stores water in Lake Powell reservoir, which is used to provide Upper and Lower Basin states with the water allotted to them by the compact. Lower Basin states depend on releases from the dam to receive their allotments. The Lees Ferry streamgage, located less than 16 miles downstream from Glen Canyon Dam, produces publicly available, real-time water data that allows the Colorado River’s streamflow below the dam to be monitored.

Most years, the Colorado River runs dry before reaching its historical terminus at the Gulf of California in Mexico, so measuring and monitoring the river at Lees Ferry is critical for the Lower Basin ecosystems, agricultural resources, and municipal industries that rely on the river’s every drop. Additionally, Grand Canyon river guides and recreationalists depend on water level data from the Lees Ferry streamgage to determine when to run rapids and camp on sandbars. Streamflow and water-quality data collected at Lees Ferry are also important for monitoring the health of the Colorado River’s aquatic life because some species, including fish and macroinvertebrates, require certain water conditions to survive, reproduce, and spawn.

The Arizona Water Science Center is responsible for maintaining and collecting water data from the Lees Ferry streamgage. The Arizona Water Science Center is a branch of the USGS dedicated to providing high quality, impartial water data to resource managers and the public for their use in understanding and managing critical water resources in Arizona and the Southwest.

Trends in subdaily to daily rainfall in Florida, 1990–2022

Fri, 5 Jun 2026 14:20:31

Changing rainfall patterns and intensifying rainfall extremes affect urban infrastructure and can increase flash-flood risk. Understanding how climate change has altered rainfall can support state and local agencies as they adapt and build resiliency. In this study, rainfall data from 23 weather stations in Florida were used to examine temporal and spatial trends over the period 1990–2022. Subdaily to daily rainfall events of durations 1, 2, 3, 6, 12, and 24 h were examined. A variety of statistical methods were applied to examine annual and seasonal trends, including quantile regression, extreme value analysis, run theory using the Mann–Kendall test, Sen–Theil slope, and Poisson and negative binomial tests, and threshold exceedance rates using generalized additive models. Using subdaily rainfall data posed challenges, including equipment failures, limited documentation of the quality assurance and control process, and potential measurement interferences. Results indicated that over 1990–2022, there was a decrease in hourly rainfall extremes but an increase at moderate quantiles. Overall, the number of rainfall events increased, particularly at shorter durations, but the mean total rainfall per event decreased. Additionally, the annual number of daily rainfall extremes showed more decreases than increases.

Co-occurrence of pesticides and pharmaceuticals and personal care products (PPCPs) across Zostera marina (common eelgrass) communities

Mon, 1 Jun 2026 13:56:29

Anthropogenic pressures are driving changes in eelgrass communities, which are altering baseline conditions in estuarine environments. Field detections have validated the transport of land-sourced pollutants to aquatic systems; however, studies rarely sample concurrently for pesticides, and pharmaceuticals and personal care products (PPCPs) across environmental compartments. Moreover, studies on contaminant uptake by eelgrass and associated species are even more limited. In collaboration with the Confederated Tribes of the Coos, Lower Umpqua and Siuslaw Indians (CTCLUSI), this study collected samples of water, eelgrass, clams, and sediment at sites of Tribal significance in Southern Oregon to test for organic contaminants (i.e., herbicides and pharmaceuticals). Paired sampling was conducted for analysis by the CTCLUSI in tandem with the United States Geological Survey (USGS) in order for the Tribe to develop analytical standards for future sampling efforts. Ten pesticides and eight pharmaceuticals were detected across the four sites, with the highest number of overall detections (27) at the Florence Marina site. The insecticide bifenthrin was most frequently detected across all media (0.012–1.565 μg/g organic carbon in sediment, 2.7–30 ng/g in organismal tissue) and the anti-diabetic agent metformin was the most detected PPCP in clam tissues (1.33–3.78 ng/g). Pesticides and PPCPs were observed to co-occur in eelgrass habitats, with numerous pesticide detections across media types. These findings demonstrate numerous routes of exposure for estuarine organisms which could be addressed with pharmaceutical disposal strategies or pesticide use restrictions near these habitats.

Future water constraints on United States lithium mining under climate change

Trost, Jenna; Nassar, Nedal; Dunn, Jennifer — Fri, 5 Jun 2026 13:48:19

Lithium is necessary for low-carbon technologies that combat climate change, but lithium extraction is water-intensive. Changes in temperature and precipitation arising from climate change are altering water distribution, which could further strain supplies for new mines and industry, farms, and households. Here we explored how climate change, water use, and mining siting could impact lithium mining in the United States. We analyzed whether there would be sufficient water available to support the single existing and 22 proposed U.S. lithium mines at mid-century under four socioeconomic-climate scenarios and five climate models. Though dependent on socioeconomic-climate scenario, climate model, and lithium deposit type, available water supply in most subbasins would likely be unable to support new mines’ water demands, or even non-mining water demands from other sectors. Water scarcity could hinder the ability of the United States to produce enough lithium to meet domestic demand thereby necessitating higher imports.

Geochemical, mineralogical, and isotopic evidence for multi-stage genesis of the Hicks Dome REE + Y-HFSE-fluorite deposit, Illinois, USA

Thu, 28 May 2026 14:13:31

Hicks Dome hosts breccias enriched in rare earth elements (REE), Y, Th, F, Ba, Ti, Nb, and Be, alongside spatially associated lamprophyre dikes (ca. 271 Ma). Hicks Dome is located within the Illinois–Kentucky Fluorspar District, which hosts fluorite, Pb–Zn, and barite resources. This study investigates the genetic relationships between Hicks Dome mineralization in breccias, alkaline magmatism, and Illinois–Kentucky Fluorspar District mineralization. Lamprophyre dikes are light REE–enriched with chondrite-normalized abundances decreasing from La to Lu. The Host Breccia exhibits middle and heavy REE–enriched patterns that mirror those of the principal REE–Th host minerals, including fluorapatite, xenotime, and thorite. Textural evidence suggests recrystallization of phosphates, sulfates, and Ti–Nb oxides in the Host Breccia. U–Pb geochronology constrains multiple mineralizing events, with ages of 277 ± 18 Ma from low-Th apatite interpreted as main-stage mineralization, and 121.6 ± 9.7 Ma from high-Th apatite indicating later overprinting. O–H–C stable isotope data provide evidence for multiple stages of fluid-rock interaction and fluid mixing: (1) early magmatic fluids dissolved limestone country rock, (2) mixing between magmatic fluids and basinal brines led to main-stage mineralization in the Host Breccia, and (3) late-stage mineralization occurred following mixing of meteoric water and basinal brine. These results indicate that heavy REEs, high field strength elements, and fluorine precipitated proximal to its alkaline magmatic source because of fluid–rock interactions and fluid mixing. Subsequent fluid mixing drove late-stage recrystallization and additional fluorite formation, a process that may be similar to mineralization in the Illinois-Kentucky Fluorspar District.

Continuous and high-resolution longitudinal profiles of the water surface and riverbed elevation for 282 miles of the Colorado River from Lees Ferry to Pearce Ferry, Arizona, 2021

Tue, 26 May 2026 18:25:26

Longitudinal profiles of water surface and riverbed elevations capture key geomorphic characteristics that can be affected by water infrastructure and natural processes. Continuous water surface profiles of the Colorado River in Grand Canyon, a river influenced by two of the largest dams in the United States, have been measured infrequently. The water surface profile was first measured in 1923, 13 years before the completion of Hoover Dam, which impounded water into western Grand Canyon, and 40 years before the completion of Glen Canyon Dam, which affected streamflow and sediment supply for all of Grand Canyon. The water surface profile was next measured in 2000, 37 years after the completion of Glen Canyon Dam, although this profile did not include the segment affected by Hoover Dam. A continuous profile of riverbed elevations has never been published. Here, we present the first complete, coupled water surface and riverbed elevation profiles, collected in 2021 during a period of steady releases from Glen Canyon Dam. The profiles were constructed from positions and elevations measured by boat-based global navigation satellite systems and from bathymetry collected by multibeam sonar. Data collected by boat were supplemented by data from a photogrammetry-derived digital surface model that was created from concurrently collected aerial images. Independent measurements made by conventional total stations referenced to a common geodetic control network were used to evaluate accuracy of all measurements. The final water surface and riverbed elevation profiles improved the accuracy and precision reported for previous profiles. In this study, the mean absolute vertical accuracy of water surface elevations was 0.07 meter for 85 percent of river miles and 0.19 meter for 11 percent of river miles. For the remaining 4 percent of river miles, water surface elevations were interpolated between measured values. The profiles reported herein can be used for current assessment of Colorado River geomorphic conditions, quantification of changes in the river over time, and predictive modeling of river resources for potential future management scenarios.quantification of changes in the river over time, and predictive modeling of river resources for potential future management scenarios.

Streamflow and surface-water presence data availability across the conterminous United States: A review for headwater systems

Fri, 5 Jun 2026 13:55:33

Water is essential for life on Earth, supporting ecosystems, human health, and economic activities. Hydrology relies on observational data, and this paper discusses regional and national datasets for the conterminous United States (CONUS) publicly available as of 2023, focusing on headwaters, defined as first- and second-order streams at 1:24000 scale. It identifies 72 primary and secondary datasets and 11 repositories and argues how better integration and accessibility of hydrological data can improve research. The paper distinguishes between datasets where streamflow was the primary data collection objective and those where it was secondary. This distinction highlights opportunities to consider data from efforts peripheral to hydrology but is still useful for understanding hydrologic conditions. The analysis reveals that out of about 118 000 active and inactive stream observation sites, about 6.6% and 25% are located on first- and second-order streams, respectively. This indicates a substantial data gap for headwater systems, which account for over 77% of stream length in CONUS. Federal agencies manage 72% of hydrologic monitoring sites across all stream orders, but only 34% of these are in headwater systems. Academic institutions operate about 2% of sites, with almost half (48%) in headwater systems, focusing on ecosystem research. State agencies also operate about 2% of sites, primarily on larger systems, with 19% on headwaters. Additionally, 23% of sites are managed by multiple agencies. Spatial patterns further reveal pronounced disparities among physiographic regions. Eastern and coastal provinces show relatively dense monitoring, while central and western regions show sparse coverage. These gaps reflect historical priorities, logistical constraints, funding limitations, and the high cost of continuous instrumentation. To address biases in monitoring networks, data collection could be enhanced with low-cost monitoring, community science, and remote sensing technologies. This study also notes the benefits of long-term monitoring and prioritizing retention of streamgages with longer records.

Tracking toxins: A pilot investigation of cyanotoxins in north-central Tennessee’s surface waters and wells

Hill, Kristi Lynn; Jaegge, Andrea; Moore, Devin; Byl, Thomas — Tue, 26 May 2026 14:02:41

Cyanobacterial toxins (cyanotoxins) threaten aquatic ecosystems and human health, yet the factors influencing their production and distribution in freshwater remain unclear. In north-central Tennessee, nutrient-rich runoff from agricultural and urban areas, combined with a karst landscape that supports drinking and recreational water use, heightens the need to understand cyanotoxin behavior. To examine cyanotoxin patterns, the U.S. Geological Survey and the Tennessee Department of Environment and Conservation monitored 18 sites, including two wells under the influence of surface water, every two weeks from September 2022 to November 2024. At least one cyanotoxin was detected at all sites, with the highest concentrations in deep reservoirs and lower levels in shallow systems. Most detections occurred during summer and fall, aligning with high temperatures and rapid-onset drought. Statistical analysis indicated that increased specific conductivity and pH raised the likelihood of detecting total microcystin, likely resulting from drought conditions and nutrient-laden runoff. Additionally, dissolved microcystin showed an inverse relationship with Cumberland River water levels, and principal component analysis showed that Secchi depth, chlorophyll a, pH, temperature, and conductivity explained most water quality variability. These results help increase understanding of cyanotoxin distribution and associated water quality conditions during detections to guide future freshwater cyanotoxin monitoring studies.

Waves, watersheds, and sediment in a coral reef embayment: Towards parsimonious models of accumulation and composition

Biggs, Trent; Messina, Alex; Storlazzi, Curt — Wed, 27 May 2026 14:03:54

High sedimentation rates can damage coral reef ecosystems. Sedimentation rates are controlled by both sediment loads from watersheds and resuspension by waves and associated circulation patterns, but the outcomes are system specific and difficult to predict. The percent terrigenous (non-organic and non-carbonaceous) material in sediment is also often used as an indicator of watershed influence, but its dynamics are poorly understood. Sediment accumulation rates, particle size, and percent terrigenous were monitored quasi-monthly for one year (March 2014-April 2015) at nine sites in a coral reef-fringed embayment in American Samoa, where an aggregate quarry had increased sediment loads to the coast but mitigation reduced loads during the monitored period. Gross and net sediment accumulation rates were measured using sediment traps and SedPods (pods), respectively. Gross accumulation rates exceeded thresholds for impacts on coral health during at least one collection period at most sites, with more exceedances on the northern reef where water residence times and sediment availability are higher and corals show signs of sediment stress. Percent terrigenous of coarse sediment was higher in the traps and pods compared with the surrounding benthic sediment, indicating that some of the terrigenous sediment was advected through the bay without accumulating on the reef. The 95th percentile of hourly wave energy density (E₉₅) taken from a global wave model (WaveWatch 3) was the best predictor of gross accumulation rates of both total and carbonate sediment in a log-log regression at most (n = 6) sites (R² range 0.72-0.92), indicating a strong role of resuspension of benthic sediment. Gross accumulation rates of terrigenous sediment were not correlated with E₉₅ and only correlated with SSY at the site nearest the stream mouth, indicating that most terrigenous sediment was not from resuspended benthic material but rather from a consistent watershed source. Percent terrigenous decreased with increasing wave energy due to high accumulation rates of carbonates during periods of high wave energy. Detection of the impact of sediment mitigation at the quarry on sediment accumulation was complicated by low wave energy in the period following mitigation. The use of gross accumulation rates and percent terrigenous as indicators of the magnitude and sources of sediment accumulation over time needs to account for wave-induced resuspension, which can be modelled with a simple power function using inputs from a global wave model.

Rearing method has limited effect on post-release movement of reintroduced age-0 Lake Sturgeon

Wed, 3 Jun 2026 14:37:38

Overfishing, habitat loss, and pollution caused the extirpation of Lake Sturgeon (Acipenser fulvescens) throughout much of the Great Lakes. A Lake Sturgeon reintroduction program using two rearing strategies began in 2018 in the Maumee River, a tributary of Lake Erie. We assessed the movement of streamside or traditionally reared age-0 Lake Sturgeon using acoustic telemetry to determine if rearing strategy affected river residency, movement, and the habitat area used. Tagged sturgeon generally left the Maumee River for Lake Erie on average 3–47 days after stocking and spent most of their time in the western basin of Lake Erie. The majority of sturgeon moved through nearshore areas along the south shore of Lake Erie. While we found no differences in post-stocking movements or habitat area used between the two rearing strategies, understanding how older life stages respond to rearing strategy is needed. Adding upstream stocking sites, using source water to raise eggs or larvae if excessive straying becomes evident, and increased acoustic receiver coverage are options to facilitate and evaluate successful recovery of Lake Sturgeon.

Effects of fipronil bait pellets on two cricetid species: Potential implications for plague mitigation and wildlife conservation

Thu, 4 Jun 2026 14:58:03

We evaluated the effects of fipronil bait pellets on two cricetids that commonly occupy colonies of black-tailed prairie dogs (Cynomys ludovicianus; BTPDs): western deer mice (Peromyscus sonoriensis) and northern grasshopper mice (Onychomys leucogaster). In one experiment, bait pellets (0.96 mg fipronil/bait) were applied at 75 baits/ha to three 1.44-ha plots on a BTPD colony. Mouse abundance declined by 70% from before to 6-10 d after treatment. In a second experiment, bait pellets (0.46 or 1.52 mg fipronil/bait) were applied at 125 baits/ha to four plots (0.85-1.86 ha) on two BTPD colonies; two non-treated plots were baselines (1.09 and 2.06 ha). From before to 11-15 d after treatment, mouse abundance declined by 51%- 67% on the treated plots vs. a decline of 9% on the non-treated plots. Mouse survival from before to 11-15 d after treatment was 51% lower on the treated plots. In a third experiment, bait pellets (0.84 mg fipronil/bait) were applied at 125 baits/acre on two 1.44-ha plots on a BTPD colony; two 1.44-ha non-treated plots were baselines. Mouse survival from before to 30-44 d after treatment was 45% lower on the treated plots; the abundance of deer mice on the treated plots remained similar from before to 30-44 d after treatment, perhaps due to juvenile recruitment and/or immigration. In a laboratory experiment, 33 deer mice offered one bait pellet (0.86 mg fipronil/bait) consumed 27% of their bait, on average (range = 0-100%). Over 3 d, deer mouse mortality was estimated at 53%; mortality increased with fipronil dose, which averaged 11 mg fipronil/kg body mass (range = 3-46 mg/kg). Brain samples were available from 31 deer mice; all tested positive for fipronil sulfone, the primary mammalian metabolite of fipronil, at 19 to 61,205 ng fipronil sulfone/g. Additional experiments could determine if these findings scale up to larger landscapes.

Indicators of mercury concentration in Lake Trout: Can fish location and appearance provide information to anglers to reduce their exposure?

Laske, Sarah; Young, Daniel; Bartz, Krista; von Biela, Vanessa; Carey, Michael — Tue, 2 Jun 2026 15:16:15

Objective

People are exposed to mercury (Hg) through the consumption of fish. State and federal governments provide broad, often-generalized food safety guidance to reduce exposure; however, numerous rural fishing areas lack testing and location- or species-specific guidance. The aim of this study was to provide tangible, visible, or easily measured characteristics of Lake Trout Salvelinus namaycush that could convey information on Hg exposure to people harvesting and consuming fish where no location-specific guidance exists.

Methods

We investigated potential indicators of Lake Trout total Hg (THg) concentrations in muscle across 10 lakes in Alaska's national parks. Potential indicators, including lake, lake zone (i.e., littoral, pelagic, profundal), fish length, head size, body condition, and general appearance, were evaluated by competing linear mixed-effects models.

Results

Lake Trout THg concentrations ranged widely from 22 to 1,306 ng/g wet weight. Much of the variation (48%) in THg concentrations was attributed to differences among individual lakes, but the interaction of the fish's lake zone, body length, and head size accounted for an additional 21%. Predicted THg concentrations increased with Lake Trout length and head : body proportion, but the rate of THg concentration increase with length varied by head : body proportion and lake zone.

Conclusions

Given the overwhelming evidence of high lake-to-lake variability in Lake Trout THg concentrations, we find support for use of lake-specific guidance when data are available. When lake-specific THg concentrations are not available, the best potential way to reduce exposure is to harvest and consume Lake Trout with mean predicted THg concentrations that are within state and federal safe consumption guidelines. This included Lake Trout from surface waters (i.e., pelagic or littoral zone) that are ≤70 cm in length; if harvesting fish from deep waters (i.e., profundal zone), lower THg concentrations were found in Lake Trout with heads ≤25% of their body length. The indicators—lake zone, length, and head size—of Lake Trout THg concentrations can provide harvesters with additional information in the absence of data for specific lakes.

The Great Lakes Geologic Mapping Coalition—Working collaboratively to understand the geology of the Great Lakes Region

Lopez, Brianna; Shelton, Jenna; Marketti, Michael; Ritzel, Kate; Graham, Brandon — Tue, 26 May 2026 18:37:48

Introduction

The Great Lakes Geologic Mapping Coalition (GLGMC), commonly referred to as the “Coalition,” is a partnership between the U.S. Geological Survey (USGS), the U.S. States of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin and the Canadian province of Ontario. The member States receive funding for geologic mapping work from the USGS National Cooperative Geologic Mapping Program (NCGMP), whereas Ontario participates as a nonfunded partner. The mission of the GLGMC is to produce three-dimensional (3D) geologic maps that depict unconsolidated sediments and near-surface bedrock in the Great Lakes region of North America. Geologic maps are the basis of most earth science investigations and help support resource exploration (energy, minerals, groundwater), natural hazard mitigation, infrastructure development, and land-use planning, all of which can be used to advance economic development and strengthen national security in the Great Lakes region.

During the last few million years, the Great Lakes region has experienced repeated glacial advances and retreats, leaving behind extensive sediments, abundant natural resources, and widespread effects on the underlying bedrock geology (Swezey and others, 2022). Linked by shared histories of past glaciations, industrial agriculture, and legacy automotive, coal, steel, and manufacturing industries, the GLGMC member States collaborate to improve the understanding of the 3D distribution of the sediments overlying the region’s bedrock (fig. 1). Developing a comprehensive subsurface 3D framework of this glaciated terrain can provide earth science data to policymakers at all levels. These insights facilitate informed decisions on the exploration, use, and protection of vital resources, such as critical minerals, industrial materials, and aquifers, thereby supporting economic prosperity and the well-being of the citizens of this region.

Since its inception in 1998, the Coalition has completed more than 100 geologic mapping projects across the Great Lakes region. Each project aims to deliver geologic maps, 3D datasets, and other information that improves understanding of the geology of the Great Lakes region, with an emphasis on economic and water resources. Key deliverables include 3D geologic maps and models typically portraying sediment thickness, often derived from top-of-bedrock and borehole data. These products are developed through a combination of fieldwork, subsurface modeling, and the collection and analysis of rock and sediment cores.

To support Coalition goals, member States collaborate with scientists working on related STATEMAP, EDMAP, and FEDMAP projects. Coalition scientists also engage with Tribal Nations in the Great Lakes region to ensure that Tribal interests pertaining to Coalition work are addressed. Through this collaboration, the Coalition unites the efforts of State, Federal, and Tribal Nation stakeholders to advance geologic data production and enhance understanding of the geologic resources of the Great Lakes region.

Factors affecting benthic macroinvertebrate health in the City of Roanoke, Virginia, 2020–2023

Miller, Samuel; Aguilar, Marcus; Helsley, Logan; Entrekin, Sally — Fri, 29 May 2026 14:23:57

Major waterways in the City of Roanoke (City) have failed to meet Virginia’s aquatic life designated use since 1996. Segments of the upper Roanoke River lack healthy benthic macroinvertebrate communities which prompted a total maximum daily load (TMDL) study by the Virginia Department of Environmental Quality (VDEQ) to identify the most probable stressor(s) causing the impairment. Excess fine sediment was identified as the most probable stressor impairing benthic macroinvertebrates on portions of the Roanoke River in 2006, and a watershed implementation plan published in 2016 required communities within the impaired watershed to implement projects that would reduce the load of fine sediment entering the Roanoke River. Additional benthic macroinvertebrate sampling and stream habitat assessments along the Roanoke River and Tinker Creek (a tributary to the Roanoke River that flows through the City) revealed continued impaired conditions, and subsequent stressor identification analysis was completed in 2023. Samples collected downstream of the City on the Roanoke River and Tinker Creek generally showed more impaired conditions relative to samples collected at locations upstream of the City. Based on this evaluation, sediment and sediment-bound polychlorinated biphenyls (PCBs) were identified as probable stressors while specific conductance, total nitrogen, and sediment metals were possible stressors in Tinker Creek; however, only a sediment TMDL target was identified to address impaired benthic macroinvertebrate communities. In the Roanoke River upstream of the Niagara Dam, sediment and total phosphorus were identified as probable stressors, sediment polycyclic aromatic hydrocarbons and sediment PCB were considered possible stressors; however, the TMDL target was only for total phosphorus.

The City partnered with the U.S. Geological Survey (USGS) in 2016 to continuously monitor water quality and streamflow conditions on a major tributary of Tinker Creek, Lick Run, and by 2020, four similar monitoring stations were installed on the Roanoke River and Tinker Creek near the locations of benthic macroinvertebrate sampling. Monitored parameters included streamflow and/or gage height (water level), water temperature, pH, dissolved oxygen, specific conductance, and turbidity. Turbidity is a measure of the relative clarity of the water and was previously used to model suspended-sediment concentrations at the monitoring stations. The City also contracted Kirk Environmental, LLP (KE) to collect benthic macroinvertebrate samples and stream habitat assessments near the locations of the water-quality monitoring stations. Identified benthic macroinvertebrates were used to calculate the Virginia Stream Condition Index (SCI), a multi-metric index composed of eight biological attributes that represent elements of the structure and function of the benthic macroinvertebrate community that measure diversity, composition, and tolerance to pollution.

Study objective: In this report, benthic macroinvertebrate samples and stream habitat assessment scores collected at four locations on the Roanoke River and Tinker Creek by KE and the VDEQ between 2020 and 2023 were compared to measured water-quality and streamflow conditions prior to sampling to evaluate patterns between benthic macroinvertebrate health, water quality, and hydrology.

Patterns of recent brook trout invasion in bull trout streams in relation to habitat, source connectivity, biotic resistance, and disturbance

Voss, Nicholas; Bowersox, Brett; Nolfi, Daniel; Quist, Michael C. — Tue, 9 Jun 2026 14:49:51

Anticipating biological invasions by nonnative species is critical to effective conservation. Nonnative brook trout Salvelinus fontinalis represents one of the most widespread threats to native bull trout Salvelinus confluentus, but the factors allowing or preventing ongoing range expansions are poorly understood. We addressed this uncertainty by resampling 221 survey locations in bull trout streams in Idaho and relating shifts in brook trout occupancy to four controls on biological invasion (habitat suitability, source connectivity, disturbance, and biotic resistance to invasion). Brook trout detections increased substantially between the historical period (58 sites) and contemporary period (94 sites). Site colonizations were positively associated with water temperature and negatively associated with landscape resistance metrics (i.e., highest streamflow and gradient between a site and the nearest source) in all top models. In contrast, there was weak support for a positive association with wildfire and limited support for hydrologic distance and biotic resistance metrics. Brook trout invasions in bull trout habitat are ongoing, limited by cold temperatures, and highly influenced by dispersal barriers that may not inhibit more mobile native salmonids.

Status and understanding of groundwater quality in the San Joaquin Valley Kern County subbasin domestic-supply aquifer study unit, 2022—California GAMA Priority Basin Project

Harkness, Jennifer; Faulkner, Kirsten; Jurgens, Bryant — Tue, 26 May 2026 18:29:13

The quality of water accessed by domestic wells (here referred to as domestic groundwater resources) in the San Joaquin Valley Kern County subbasin (basin number 5-022.14) was assessed as part of the California Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project (GAMA-PBP), in cooperation with the California State Water Resources Control Board. Kern County is at the southern end of the San Joaquin Valley in California, and about 30,000 residents are estimated to use privately owned domestic wells for drinking water. Domestic wells typically draw from shallower parts of the aquifer system than public-supply wells and can be more vulnerable to effects from surface activities. Kern County is host to a highly productive agricultural industry, with Bakersfield as the main urban center. The Kern River runs through Bakersfield from the southern Sierra Nevada and intersects the Kern Water Bank, one of the largest groundwater banking operations in California, at the Kern River Intertie. The section of the Kern River running through the Kern Water Bank is dry most years. Kern County also encompasses some of the most productive oil and gas basins in California, with extensive underground and surface disposal of oil-field wastewater.

This study was based on data collected from 33 sites sampled by the U.S. Geological Survey for the GAMA-PBP in 2022. To provide context for the water quality assessment, measured concentrations were compared to regulatory and non-regulatory health-based and aesthetic benchmarks. A grid-based method was used to estimate the proportions of the groundwater resources used for domestic-supply wells that have water-quality constituents below (low relative concentration), approaching (moderate relative concentration), or above (high relative concentration) benchmark concentrations. At least one measured constituent with a regulatory benchmark was categorized as having a high relative concentration in 72 percent of the aquifer area used for domestic groundwater resources. Inorganic constituents were detected at high concentrations in 45 percent of the domestic groundwater resources, and the constituents detected above regulatory benchmarks were arsenic, nitrate, and uranium. At least one organic constituent was detected at high concentrations in 41 percent of the domestic groundwater resources, and the constituents exceeding regulatory benchmarks were the fumigants 1,2,3-trichloropropane (1,2,3-TCP), 1,2-dibromo-3-chloropropane (dibromochloropropane [DBCP]), 1,2-dibromoethane (EDB), and the per-and polyfluoroalkyl substance (PFAS) perfluorooctanesulfonate. The disinfection by-product chloroform, the fumigant 1,2-dichloropropane, the herbicides atrazine and hexazinone, and the herbicide degradates 2-chloro-6-ethylamino-4-amino-s-triazine, 2-chloro-4,6-diamino-s-triazine, 4-hydroxychlorothalonil, and metolachlor sulfonic acid were detected in more than 10 percent of domestic groundwater resources, but concentrations did not exceed regulatory benchmarks.

Land use, groundwater age (fraction of modern water and mean age), and geochemical environment (oxic or anoxic conditions, pH, alkalinity) were associated with the distribution of high relative concentrations of inorganic and organic constituents. Young, oxygenated water is recharged along the Kern River and adjacent recharge ponds, or as irrigation water in the agricultural areas. High concentrations of nitrate and volatile organic compounds occurred in the oxic water in urban and agricultural areas. The fumigants 1,2,3-TCP, DBCP, and EDB were reported throughout the agricultural areas, whereas chloroform, tetrachloroethene, and PFAS were associated with urban land use. High uranium concentrations were associated with young, modern groundwater in agricultural areas with low pH and high bicarbonate. Total dissolved solids increased with distance from the Kern River, as the contributions of fresh, oxic water decreased. High concentrations of arsenic were present in older anoxic or alkaline groundwater away from areas of recharge. Overall, groundwater age, redox conditions, and the source of recharge as a result of different land uses contribute to large aquifer-scale portions of domestic groundwater resources that exceed health-based benchmarks for nitrate, uranium, and fumigant concentrations.

Precipitation-based flood-inundation maps for the East Fork Little Blue River and tributaries at Lee’s Summit, Missouri, 2024

Atkinson, Allison — Tue, 26 May 2026 18:19:14

The U.S. Geological Survey, in cooperation with the City of Lee’s Summit, Missouri, assessed flooding of the East Fork Little Blue River and tributaries for varying precipitation magnitudes and durations, varying antecedent runoff conditions, and projected climate-change conditions. The precipitation scenarios were used to develop a library of flood-inundation maps for a 2.95-mile reach of the East Fork Little Blue River and tributaries within the city.

A two-dimensional U.S. Army Corps of Engineers Hydrologic Engineering Center–River Analysis System (HEC–RAS; ver. 6.5) rain-on-grid model was calibrated to selected runoff events representing a range of antecedent runoff conditions and hydrologic responses. Lowest adjacent grades for structures within the nearby study area were incorporated into the terrain, and depth grids and water-surface elevation grids were developed for the study area. Simulated velocities at selected bridge locations were also developed from the model. The model was calibrated using water-surface elevation data collected from water-level loggers (pressure transducers) and streamflow measurements and water-surface elevation measurements made at a reference point during runoff events. The calibrated HEC–RAS model was used to simulate streamflows from design rainfall events of 15-minute to 24-hour durations and ranging from a 100- to 0.1-percent annual exceedance probability (1-year to 1,000-year recurrence intervals). Flood-inundation maps were produced for depths at a reference location of 3 to 16 feet, or a depth exceeding the 0.1-percent annual exceedance probability interval precipitation. The results of each precipitation duration-frequency value were represented by a 1-foot-increment inundation map based on the generated peak streamflow from that rainfall event and the corresponding water-surface elevation at the East Fork Little Blue River reference location.

Within the HEC–RAS model, 240 scenarios were developed from the design rainfall events with each of 3 antecedent conditions. Additional scenarios were created to simulate the effects of projected precipitation scenarios on the 100-year recurrence interval, 24-hour storm and the 100-year recurrence interval, 6-hour storm. All simulation results were assigned to a flood-inundation map condition based on the generated peak flow and corresponding water-surface elevation at the East Fork Little Blue River reference location.

The flood-inundation maps are shown on a web mapping application made available to the public through the City of Lee’s Summit (hyperlink will be added when available). The flood-inundation maps are tied to real-time precipitation data obtained from the Automated Surface Observing System weather station at the Lee’s Summit Municipal Airport, accessible at https://mesonet.agron.iastate.edu/request/download.phtml?network=MO_ASOS. The availability of these maps, along with information regarding observed rainfall, could help provide emergency management personnel and residents with information that is critical for flood-response activities, such as evacuations and road closures, and for postflood recovery efforts.

Distribution, abundance, breeding activities, and restoration efforts for the Southwestern Willow Flycatcher at Marine Corps Base Camp Pendleton, California—2025 Annual Report

Lynn, Suellen; Howell, Scarlett; Kus, Barbara E. — Mon, 18 May 2026 14:01:33

Executive Summary

The purpose of this report is to provide the Marine Corps with an annual summary of the distribution, abundance, and breeding activity of the endangered Southwestern Willow Flycatcher (Empidonax traillii extimus; flycatcher) and to present results of management actions implemented to attract flycatchers and enhance flycatcher habitat at Marine Corps Base Camp Pendleton (MCBCP, or Base). Surveys for the flycatcher were done on Base between May 6 and July 23, 2025. All MCBCP’s historically occupied riparian habitat (core survey area) was surveyed for flycatchers in 2025. None of the non-core survey areas were surveyed in 2025.

No resident flycatchers were detected on Base in 2025. The one resident (female) present in 2024 did not return to the territory she occupied in 2024, and she was not detected within the historically occupied habitat surveyed in 2025.

Eight transient Willow Flycatchers of unknown subspecies were observed on two of the five drainages surveyed in 2025: Las Flores Creek and the Santa Margarita River. No Willow Flycatchers were detected at Fallbrook, Pilgrim, or San Mateo Creeks. Transients in 2025 occurred in mixed willow and riparian scrub habitats, dominated by multiple willow species (Salix spp.). Exotic vegetation was recorded in most flycatcher locations and was dominant (cover of exotics greater than 50 percent) in more than half of all transient locations. The most common exotic plant in habitat used by flycatchers was poison hemlock (Conium maculatum). All six of the flycatchers that were observed closely enough to determine banding status were unbanded.

Two measures were initiated in recent years to attract and retain resident breeding flycatchers on MCBCP: conspecific attraction using flycatcher song broadcasts and installation of artificial seeps to enhance flycatcher habitat. We surveyed plots with and without speakers that broadcast flycatcher vocalizations throughout the breeding season and detected two transient Willow Flycatchers within 20 meters of one speaker in 2025. We set up permanent vegetation sampling points surrounding artificial seeps and nearby sites without artificial seeps (Reference sites) to determine the effects of surface-water enhancement by seep pumps. Vegetation cover was highest near the ground and decreased with increasing height. Woody vegetation made up most of the cover at all height categories. Soil saturation in 2025 was higher at the sites near seeps than at the Reference sites and was associated with higher native herbaceous cover and lower non-native cover.

Continuous stream discharge, salinity, and associated data collected in the lower St. Johns River and its tributaries, Florida, 2023

Carson, Jennifer N.; Benacquisto, Matthew T. — Wed, 27 May 2026 13:00:48

The U.S. Army Corps of Engineers, Jacksonville District, deepened the St. Johns River channel in Jacksonville, Florida, to accommodate larger, fully loaded cargo vessels. The U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers, monitored stage, discharge, and (or) water temperature and salinity at 26 continuous data collection sites in the St. Johns River and its tributaries.

This report contains information collected during the 2023 water year, from October 2022 to September 2023. Data at each site were compared for the length of the project, 8 years so far, and on a yearly basis to show the annual variability of discharge and salinity.

The countywide annual rainfall for the 2023 water year was below the average yearly rainfall in four of the five counties. Annual mean discharge at 9 of the 10 tributary monitoring sites was lower for the 2023 water year than for the 2022 water year, and the annual mean flow at Broward River below Biscayne Boulevard near Jacksonville, Florida (USGS site number 02246751), was the lowest recorded at that site for the 8 years of data collection. The annual mean discharge for each of the main-stem sites was higher for the 2023 water year than for the 2022 water year and was above the average for the 8 years of data collected so far.

Among the tributary sites, annual mean salinity was highest at Clapboard Creek above Buckhorn Bluff near Jacksonville, Fla. (USGS site number 302657081312400), the site closest to the Atlantic Ocean, and was lowest at Durbin Creek near Fruit Cove, Fla. (USGS site number 022462002), the site farthest from the ocean, for all years. Annual mean salinity data from the main-stem sites indicate that salinity decreased with distance upstream from the ocean, which was expected. Annual mean salinity for the 2023 water year was higher than or equal to that of the 2022 water year for all main-stem and tributary sites, except at St. Johns River at Dancy Point near Spuds, Fla. (USGS site number 294213081345300), which was lower. Three main-stem monitoring stations (USGS site numbers 295856081372301, 02245340, and 301057081414800) and six tributary monitoring stations (USGS site numbers 300803081354500, 022462002, 301204081434900, 02246459, 02246518, and 02246804) either had the highest annual mean salinities or tied with the highest annual mean salinities at their respective sites since data collection began.

Melanoma and other melanistic lesions in brown bullhead Ameiurus nebulosus from waterbodies in the northeastern United States and Canada: Identification of risk factors

Thu, 4 Jun 2026 19:56:25

Melanistic lesions, including non-raised black areas due to proliferations of melanocytes and melanomacrophages in the dermis and epidermis, as well as raised black areas consistent with melanoma, are described in brown bullhead (BBH) Ameiurus nebulosus from three water bodies in the northeastern United States and Quebec, Canada. First observed in the Vermont portion of Lake Memphremagog, Vermont, USA and Quebec, Canada, the prevalence of melanistic lesions during 2014–2020 was greater than 30% in BBH 200 mm and longer. In 2023, seven sites throughout the lake were assessed, and prevalence ranged from 18% to 42%. In Hermon Pond, Maine, the prevalence was 29% in 2024, and in Village Pond, New Hampshire, lesions occurred in 22% of BBH in 2025. Compared to skin from visibly normal BBH, skin with melanistic lesions had significantly higher concentrations of seven metals, including arsenic, a known carcinogen and zinc. Lesions associated with oxidative damage, such as the accumulation of ceroid/lipofuscin, were also observed in the gill, spleen and kidney tissue of both affected and visibly normal BBH. The progression of lesions, observed by histopathology, ranged from inflammation, signs of oxidative damage, proliferation and necrosis of club cells, and the presence of melanomacrophages and melanocytes in the epidermis to invasive melanoma and suggests chronic exposure of BBH to environmental initiators and promoters of carcinogenesis.

Advancing monitoring approaches to enhance tidal Chesapeake Bay habitat assessment for submerged aquatic vegetation, water clarity, chlorophyll a and dissolved oxygen

Mon, 8 Jun 2026 13:52:36

Water quality monitoring capacity has been declining for the Chesapeake Bay Program (CBP) at a time when information needs are growing, and data gaps exist to address critical decision-support for managers. The CBP Scientific Technical Assessment and Reporting Team is leading a Principal’s Staff Committee requested gap analyses toward understanding support needed to improve water quality monitoring and analysis programming. Advanced technologies and alternative monitoring approaches in the form of satellite-based measurements, Artificial Intelligence/Machine Learning (AI/ML) algorithms for data interpretation, continuous water quality in-situ sensor arrays, and community science efforts offer a growing portfolio of valuable opportunities for expanding data collections and analysis program capacities. However, since 1985, each of these options are examples of growing opportunities to enhance water quality assessments yet has seen limited adoption into elements of Chesapeake Bay water quality monitoring programs. Where new technologies have been adopted (e.g., shallow water continuous water quality monitoring), such temporally rich data streams have supported Bay health insights yet had limited use in regulatory water quality criteria assessment.

This Scientific Technical Advisory Committee (STAC) supported workshop provided the ideal forum for engaging our CBP partnership regarding the maturity of new and evolving monitoring and analysis capacities to address program information needs while appreciating limitations with adopting new tools and approaches. Improving natural resources monitoring efficiency and effectiveness will expand the scientific and technical foundations for making robust, strategic choices on decisions for CBP Partnership community-based priorities, policies, and management actions.

Workshop findings and recommendations reflect progress in science, technology, and analyses addressing long-standing programmatic limitations in data collection and analysis capacities. State-of-the-science updates highlighted in the workshop span the spectrum of efforts representing improvements, successes, remaining challenges toward operationalizing protocols, and guidance toward research, or adoption and implementation by monitoring programs.

Baseflow and snowmelt sustained streamflow in the Upper Colorado River Basin, 1986-2020

Mon, 18 May 2026 15:41:10

The Upper Colorado River Basin (UCRB) faces substantial water availability limitations. Although most streamflow originates as snowmelt, the partitioning of snowmelt between surface runoff and groundwater recharge and subsequent groundwater discharge to streams is highly uncertain. On average, over half of the streamflow in the UCRB is estimated to originate from groundwater discharge to streams, highlighting the importance of baseflow in sustaining surface water. However, the historical patterns of baseflow and streamflow, along with their variability over space and time and their specific sources, remain unknown at the basin scale. This study addresses those gaps by characterizing the sources and transport pathways of both baseflow and streamflow in the UCRB at a seasonal timestep from 1986 to 2020, including the lagged delivery of subsurface water to streams beyond the current season, using coupled models of baseflow and streamflow. Between 1986 and 2020, on average 63% of UCRB streamflow originated from baseflow. About half of this baseflow took longer than one season to reach streams, and outside the snowmelt season, baseflow was the dominant source of streamflow. Snowmelt was a key source of both baseflow and streamflow. Current season snowmelt contributed 33% of streamflow via runoff, and 22% of the 29% of streamflow that originated as current season baseflow via subsurface flow to streams. Over the study period, baseflow index (BFI) declined in headwaters and increased at mid-elevations. Springtime increases in BFI demonstrate the increasingly important role baseflow plays in water supply. Identifying the sources, locations, and timing of water that contributed to the UCRB outlet can inform management of water resources in the basin.

VegET evapotranspiration for Africa: Continental-scale simulation, multi-product evaluation, and drought assessment

Mon, 18 May 2026 15:28:47

Study region

Continental Africa, encompassing diverse climatic zones—tropical, arid, and temperate—and spanning major transboundary river basins such as the Nile, Niger, Congo, Volta, and Zambezi River Basins. The region exhibits pronounced hydroclimatic gradients and heterogeneous land use systems ranging from rainfed croplands and rangelands to dense tropical forests and irrigated schemes.

Study focus

Actual evapotranspiration (ETa) is a central component of the terrestrial water balance, governing the redistribution of water and energy between the land surface and the atmosphere. Accurate estimation of ETa at continental scale is critical for hydrological monitoring, water resource management, and climate adaptation, as well as for quantifying water, energy, and carbon fluxes that underpin sustainable development. In this study, we applied the agro-hydrologic VegET v2 model to simulate a new, high-resolution, continental-scale ETa dataset for Africa (2000–2021). The model results were benchmarked against four widely used remote sensing-based products—MODIS16 v6.1, SSEBop v6.1, WaPOR v3, and GLEAM v4.1a—across major climate zones, land use types, and River Basins, providing a comprehensive multi-product evaluation of evapotranspiration dynamics across the continent.

New hydrological insights for the region

Validation against eddy covariance flux tower observations at eight representative sites confirmed that VegET v2 accurately reproduces the seasonal dynamics of observed ETa, achieving a correlation (r) of 0.8 and an RMSE of 25 mm month⁻¹ —accuracy that is comparable to or higher than accuracies of satellite-based products MODIS16, SSEBop, and GLEAM. This study represents one of the first Africa-wide hydrological simulations of ETa, extending the VegET model beyond basin-scale applications. Intercomparisons reveal that VegET aligns closely with MODIS16, SSEBop, and GLEAM in humid and tropical regions (r = 0.80–0.90; RMSE < 20 mm month⁻¹), while greater discrepancies appear in arid and semi-arid zones, where WaPOR tends to overestimate ETa (RMSE ≥ 28 mm month⁻¹). Despite these differences, VegET effectively captures spatial and temporal ETa variability across rainfed croplands, forests, and savannas, supporting its utility in regional water balance assessments, water accounting, and drought monitoring. A key application of VegET v2 is the Evapotranspiration Deficit Index (ETDI), derived by integrating VegET-based ETa with potential evapotranspiration (PET) to quantify water stress. ETDI successfully captured major drought episodes across Africa, including persistent Sahelian and southern African dry spells, the 2020–2021 winter drought in the Maghreb, and the 2018–2019 austral summer drought in southern Africa, while identifying positive anomalies over central Africa indicative of recurrent wetness. These results underscore VegET’s capability as a hydrologically consistent, operational tool for continental ETa monitoring and drought assessment, offering support for basin-scale water balance studies, food security planning, and climate resilience across Africa’s diverse hydrological environments.

Evaluation of stream capture related to groundwater pumping, middle Humboldt River Basin, Nevada

Fri, 15 May 2026 17:59:27

Historical, future, and potential stream capture from groundwater pumping in the middle Humboldt River Basin (MHRB), Nevada, is estimated using a calibrated numerical groundwater flow model. The model was developed to estimate (1) stream capture, which is the change in flux between the groundwater system and the Humboldt River and tributaries, and (2) change in streamflow, which is the change in streamflow estimated for the Imlay gage on the Humboldt River (U.S. Geological Survey streamgage 10333000). Historical stream capture for water years (WYs) 1961–2015 is estimated using recorded and estimated groundwater pumping during that period. Future (predictive) stream capture was based on historical stresses (WYs 1961–2015) using a scenario that simulated non-mine pumping from WY 2015 at a uniform rate for 100 years into the future. Potential stream capture throughout the middle Humboldt River Basin from groundwater pumping during varying durations of time are presented in a series of capture maps. Maps also are presented that show the potential to capture from groundwater evapotranspiration, as well as the storage changes for pumping duration of 100 years.

Estimates of historical stream capture from the mainstem Humboldt River during the early 1960s are less than 400 acre-feet per year (acre-ft/yr) when groundwater withdrawals and pumping rates were relatively small compared to more recent times. In the late 1980s and early 1990s, groundwater withdrawals increased and estimated historical stream capture also increased from about 4,000 acre-ft/yr in the late 1980s and early 1990s to as much as 18,800 acre-feet (acre-ft) in WY 1998. In WY 2015, estimated historical stream capture declined to about 13,000 acre-ft because of decreasing groundwater withdrawals and lower streamflow during the drought of WYs 2012–15, resulting in less stream water available for capture. Stream capture was estimated for 100 years into the future based on WY 2015 non-mine pumping rates and mine-dewatering activity through WY 2015. Stream capture is forecast to increase to about 23,000 acre-ft/yr, and streamflow in the Humboldt River could decrease by as much as 19,000 acre-ft/yr.

Pumping for mine-dewatering and the associated discharge of that water affects streamflow in the Humboldt River at Imlay, Nevada (U.S. Geological Survey streamgage 10333000). Historically, from WYs 1991 to 2015, streamflow was greater at Imlay gage during active mine-dewatering from mine-water discharge operations and increased by as much as 105,000 acre-ft in WY 1998. The increase was attributed mostly to the discharge of groundwater from mine-related dewatering operations directly into the mainstem Humboldt River or its tributaries, with some of this increase associated with return flows from discharge to rapid infiltration basins. Results indicate that streamflow at Imlay gage is expected to decrease by as much as 1,600 acre-ft/yr 30 years after mine-related pumping and discharge are discontinued. The streamflow reductions at the Imlay gage are expected to then decrease to around 500 acre-ft/yr, 100 years after mine-related pumping and discharge are discontinued.

Potential capture maps were produced for pumping durations of 10, 25, 50, and 100 years. Capture map results indicate that areas of greater potential stream capture occur adjacent to the Humboldt River and for upstream tributaries areas north of the Humboldt River.

Timing, uncertainty, and opportunity cost: Lessons for ecosystem modification on the Colorado River

Mon, 18 May 2026 14:54:02

While conservation goals have long been pursued through traditional species-augmenting actions, a broader set of episodic ecosystem modification (EEM) actions, such as hydropower dam releases, prescribed fire, and beach nourishment, is garnering attention. EEM actions face several implementation challenges stemming from high opportunity costs, delayed effect mechanisms, reliance on monitoring for deployment timing, and outcome uncertainty due to infrequent use. In this paper, we study the use of EEM actions in the form of designer flows—ecologically-motivated releases of water into regulated river segments—to maintain a viable population of a threatened native fish species in the Colorado River. We demonstrate how the cost-effectiveness of EEM actions can be hampered by the complex and delayed effects on species viability, but enhanced through targeted monitoring for timing deployment and experimentation for reducing uncertainty about effectiveness.

Storm surge barriers reduce seaward sediment supply to lagoonal estuaries

Ralston, David; Orton, Philip; Warner, John C.; Kasaei, Shima — Thu, 14 May 2026 13:56:24

Numerical simulations with realistic forcing of fixed infrastructure for a proposed storm surge barrier for a lagoonal estuary, Jamaica Bay (New York, USA), are analyzed during typical forcing conditions to assess alterations to flow and sediment transport with the barrier open. Lagoonal estuaries are shallow and have modest watershed freshwater and sediment inputs, so sediment delivery is primarily from offshore by tidal transport. The storm surge barrier infrastructure across the inlet channel reduces cross-sectional area and increases tidal velocities, increasing frictional and form drag. The overall reduction in tidal amplitude is about 1%, but the quarterdiurnal M₄ component decreases by 11%. The salinity and stratification in the estuary are only slightly modified by mixing by stronger velocities near the barrier. Sediment transport in the inlet scales approximately with tidal velocity cubed and net landward transport is driven by flood-dominant tidal asymmetry. Additionally, tidal asymmetry in the jet flow through barrier openings causes a divergence in sediment transport within several kilometers. The alterations to the tidal currents reduce sediment import to the bay by 20% for fine sand; transport of sediment with slower settling velocities is less affected, with reductions of 3% for medium silt and <1% for fine silt. The study examined tidal exchange with an open barrier, but the overall impact also depends on barrier operations during major storm events. The impacts of barrier infrastructure on lagoonal estuaries are distinct from other estuary types due to their modest freshwater input, predominance of tidal transport, and offshore sediment supply.

Salinas Valley integrated hydrologic and reservoir operations models, Monterey and San Luis Obispo Counties, California

Fri, 15 May 2026 17:52:16

The area surrounding the Salinas Valley groundwater basin in Monterey and San Luis Obispo Counties of California is a highly productive agricultural area, contributes substantially to the local economy, and provides a substantial portion of vegetables and other agricultural commodities to the Nation. This region of California provides about half of the Nation’s lettuce, celery, broccoli, and spinach each year. Thus, this agricultural area provides substantial volumes of agricultural products not just for California but for the United States.

Changes in population and increased agricultural development, which includes a shift toward more water-intensive crops, and climate variability, have put increasing demand on both surface-water and groundwater resources in the valley. This situation has resulted in water management challenges in the Salinas Valley that generally relate to the distribution of the water supply throughout the basin. Where and when the water is present in the surface and subsurface does not coincide with where and when the water is needed. Historically, to deal with the distribution issue, water has been used conjunctively in the valley. Conjunctive use is a water management strategy that coordinates surface-water and groundwater use to maximize water availability. Groundwater is used throughout the Salinas Valley to meet water demands when surface-water supplies are insufficient. The availability of surface water is constrained by climate. Precipitation and streamflow vary seasonally and year to year. Although there are two reservoirs in the Salinas Valley to capture and store water during wet periods, the only conveyance of reservoir water to coastal agricultural areas is the Salinas River. Increasing demand for groundwater and surface-water resources throughout the Salinas Valley has resulted in undesirable effects from unsustainable water use, such as surface-water depletion, groundwater-level declines, storage depletion in the principal aquifers, and seawater intrusion. To address these escalating issues, local communities, water management agencies, and groundwater sustainability agencies are evaluating how to sustainably manage both their surface-water and groundwater resources. To meet water demands and reduce the undesirable effects of unsustainable water use, continued conjunctive management of surface water and groundwater would ideally incorporate strategies to deal with increases in demand and climate variability.

To evaluate the challenging water management issues in the Salinas Valley, the U.S. Geological Survey, Monterey County Water Resources Agency, and the Salinas Valley Basin Groundwater Sustainability Agency developed a comprehensive suite of models that represent the Salinas Valley hydrogeologic system called the Salinas Valley System Model. The geologic framework is known as the Salinas Valley Geologic Framework and was developed to characterize the subsurface using various topographic and geologic data sources, including information on hydrogeologic units, their surfaces and extents, geologic structures, lithology, and elevations from borehole data and cross sections, as well as details on faults and existing models. The surface-water model is called the Salinas Valley Watershed Model and simulates the Salinas River watershed. Monthly surface-water inflows into the integrated hydrologic model domain were simulated using the Salinas Valley Watershed Model. The historical model uses historical climate data, water and land use data, and reservoir releases to simulate agricultural operations, including landscape water demands, diversions, and reclaimed wastewater. The operational model adds an embedded reservoir operations framework to the simulation of the historical model that allows specified operational rules to simulate reservoir releases and changes in reservoir storage. The operational model assumes current reservoir operations and constant land use, which differs from historical conditions. Thus, the operational model is a hypothetical baseline model that can be used by local water managers to evaluate and quantify potential benefits of water supply projects. Together, the geologic framework, watershed, historical, and operational models form a tool that can be used to simulate irrigated agriculture and associated reservoir operations of the integrated hydrologic system of the Salinas Valley.

Toxicity of synergized permethrin residues in cattle dung to two temperate dung beetle species after application of common livestock pour-on treatment

Tue, 19 May 2026 15:19:53

Essential to pasture health, dung beetles (Coleoptera: Scarabaeidae) provide key ecosystem services across natural and managed rangeland habitats. Insecticide residues in livestock dung can negatively impact dung beetle populations, and synergized pyrethroid products are commonly used to combat resistant pest fly populations. Here, permethrin residues were measured by GC-MS/MS in fresh cattle feces on Days −2 (pretreatment), 4, 8, 16, and 30 after the label rate application of a formulated pour-on treatment (a.i. 5% permethrin, 5% piperonyl butoxide [PBO]). Mean (± SE) measured permethrin concentrations were the highest on Day 4 at 1400 ± 360 ng of permethrin/g of dung (dry weight) with a maximum concentration of 2200 ng/g. Approximately, 99% of applied permethrin was excreted by Day 16, with no detection by Day 30. Field-collected dung was used in a 48-hour toxicity test and with three treatment groups (control [Day −2], low risk [Day 16], and high risk [Day 4]). Two temperate dung beetle species were tested: Onthophagus pennsylvanicus Harold and Canthon chalcites Haldeman. Mean (± SE) mortality of O. pennsylvanicus was 28 ± 5% and 58 ± 13% for low and high risk treatments, respectively. Mean (± SE) mortality of C. chalcites was lower than O. pennsylvanicus with 10 ± 4% and 40 ± 10% for low and high risk treatments, respectively. PBO was detected on Days 4 and 8, and the permethrin:PBO ratio was 10:1 on Day 4, i.e., high risk treatment. Data presented highlight episodic risks of pour-on products and support threshold-based, integrated pest management approaches.

Top Elevation of Glacial Till and Thickness of the Big Sioux Aquifer Delineated From Electrical Resistivity Tomography Surveys Near Sioux Falls, South Dakota, 2022 and 2025

Medler, Colton; Anderson, Todd — Fri, 15 May 2026 17:44:04

The City of Sioux Falls, South Dakota, requested the U.S. Geological Survey perform electrical resistivity surveys on three parcels of land north of the city. Electrical resistivity data were collected along a total of 22 transects during March 14–18, 2022, and November 17–21, 2025. Results from electrical resistivity surveys were used to delineate the top of glacial till deposits for the purpose of characterizing the Big Sioux aquifer near the city. Delineating geologic contacts provides important information on groundwater storage, flow dynamics, well design and placement, contaminant transport, groundwater–surface-water interactions, and regional water modeling. The top elevation of glacial till and the thickness of the Big Sioux aquifer varied among the three survey areas. The interpreted top elevation of glacial till in the North survey area decreases from east to west toward a slough, with elevations ranging from 1,403 to 1,418 feet (ft). The estimated thickness of the Big Sioux aquifer in the North survey area increased from east to west, with thicknesses ranging from 23 to 38 ft. The top elevation of glacial till in the Well 72 survey area generally decreases from northwest to southeast. Top elevations of the glacial till in the Well 72 survey area ranged from 1,400 to 1,409 ft along the southern end of transect W72_2. The estimated thickness of the Big Sioux aquifer in the Well 72 survey area was greatest along a southeast to northwest trending channel, with thicknesses ranging from 28 to 40 ft. The top elevation of glacial till in the Nose survey area generally decreases west toward the Big Sioux River. Top elevations of the glacial till in the Nose survey area ranged from 1,362 to 1,395 ft. The estimated thickness of the Big Sioux aquifer in the Nose survey area ranged from 33 to 70 ft.

Calcareous nannofossil assemblage changes in the Surprise Hill core and their implications for floral response to the Paleocene-Eocene Thermal Maximum across the Salisbury Embayment of Virginia, USA

Tue, 19 May 2026 15:07:35

We present Paleocene-Eocene calcareous nannofossil biostratigraphy and paleoecology for the Surprise Hill core, U.S. Atlantic Coastal Plain, Virginia. Calcareous nannofossil datums ranging from Zone NP3 to NP14 were identified. The Danian-aged Brightseat Formation rests unconformably atop the Lower Cretaceous Potomac Group at 211.4 m and disconformably underlies the Aquia Formation at 208.8 m. The absence of Zone NP7 suggests a hiatus is present in the Aquia Formation (Zones NP5 – NP9a). The contact between the Marlboro Clay and the overlying Nanjemoy Formation (Zones NP10 – NP14) at 189.5 m is truncated. The Paleocene-Eocene transition is marked by a shift from glauconitic sands of the Aquia Formation to pelitic muds of the Marlboro Clay at 202.7 m. A 3–3.5‰ negative δ¹³C excursion of benthic foraminifer and a thin dissolution interval (201.6–202.5 m) are recorded in the basal Marlboro Clay. Nannofossil response to the Paleocene-Eocene Thermal Maximum (PETM) include (1) a bloom in taxa with affinities for changing salinity conditions just prior to the PETM basin wide (Hornibrookina australis arca), (2) a decline in taxa with ecological affinities for cool, eutrophic waters (Chiasmolithus bidens) during PETM, (3) fluctuations in mesotrophic to eutrophic, opportunistic taxa (e.g., Neochiastozygus junctus) during PETM, (4) successive turnovers in species of Toweius spp. during core-PETM and its recovery. Our findings suggest that overall nannofossil assemblages in the southernmost portion of the Salisbury Embayment responded similarly to assemblages from South Dover Bridge, but had differing response to local changes in nearshore paleoecology.

Watershed Continuum Monitoring Approach: Combining multiple water quality patterns along stream and river flowpaths to track sources, pathways, and processing of pollutants

Wed, 13 May 2026 14:33:57

There is a growing need to improve and expand water quality monitoring approaches to more accurately track the sources, fate, and transport of multiple chemicals and pollutants holistically and quantify the effects of best management practices (BMPs) at the watershed scale. An overarching question raised by scientists, environmental managers, and the general public is: how far can water quality impacts from disturbances or benefits from watershed management and restoration propagate along stream and river flowpaths? Many studies using the classic watershed approach focus on analyzing changes in water quality over time at one or a few sampling stations, whereas theories such as the River Continuum Concept focus on predicting shifts in energy sources and biological communities along rivers but have not been directly applied to water quality. We propose to merge these concepts to create a Watershed Continuum Monitoring Approach (WCMA) that combines both spatial and temporal monitoring in order to better detect and quantify trends and transitions in multiple water quality indicators along flowpaths. Specifically, an array of multiple water quality indicators are analyzed at multiple downstream points along a watershed flowpath over time. These multiple water quality indicators are analyzed together for making comparisons to infer hydrological, biological, and geochemical processes controlling sources, transport, and attenuation of pollutants (e.g., analagous to stream tracer studies at the watershed scale). The WCMA leverages the natural expansion of watershed areas along a flowpath, which reflect transitions in land use, land cover, and environmental management across spatial and temporal dimensions for making direct comparisons across different stream reaches and spatial trend analysis. WCMA facilitates monitoring of multiple water quality indicators together, and identifcation of hot spots in sources and attenuation of pollutants or mixtures of pollutants. We illustrate practical applications of the WCMA to analyze water quality trends, transitions, and tradeoffs (i.e., a tradeoff occurs when one pollutant is reduced but another is directly or indirectly increased downstream). We explore case studies that quantify: (1) downstream reductions in concentrations of multiple pollutants along a stream flowing to a major drinking water source due to engineered and nature-based solutions, (2) downstream reductions in multiple pollutants and water quality tradeoffs along streams experiencing stormwater BMPs and stream restoration, (3) comparisons in downstream reductions of multiple pollutants and nutrient uptake along streams draining into major drinking water sources based on types of stream restoration, (4) comparisons of downstream pollutant reductions along streams experiencing riparian forest conservation vs. stream restoration, and (5) mapping and visualizing hot spots of increasing water quality problems such as hypoxia, contaminant mobilization, and freshwater salinization that extend downstream to tidal rivers of the Chesapeake Bay. We explore future applications of WCMA for tracking decreasing trends in salinity, E. coli, and other pollutants of emerging concern. WCMA can holistically inform progress towards achieving multiple water quality goals and also be used as a screening tool for selecting monitoring sites and targeting management in strategic locations. Overall, WCMA enables the simultaneous quantification and comparison of sources and transport and attenuation rates for different chemicals and pollutants across a broader range of watershed sizes and flowpath lengths, which is critical for understanding ecological, hydrological, geochemical, and biogeochemical processes along human-impacted streams and rivers.

Effects of wildfire on soil hydraulic properties in the western Oregon Cascades

Pimont, Cedric; Thaler, Evan; Ebel, Brian A.; Bladon, Kevin — Thu, 14 May 2026 13:32:52

Wildfires can substantially impact the hydrology of forested watersheds, increasing the risk of hydrologic hazards such as flash floods and debris flows. Soil hydraulic properties related to infiltration are a key control in determining the timing and magnitude of these hydrogeomorphic events. In our study, we collected 445 soil cores from burned (216 cores) and unburned (229 cores) reference catchments and analyzed them for soil hydraulic properties 10 months after the 2022 Cedar Creek Fire in Oregon, USA. We observed significantly greater field-saturated hydraulic conductivity (K_fs), sorptivity (S), and wetting front potential (Ψ_f) in burned soils relative to unburned soils, with median ratios of 5.7, 4.4, and 5.0, respectively. Among low-, moderate-, and high burn severity groups, soil hydraulic properties were not statistically different. Reductions in median soil bulk density with increasing burn severity suggested an expansion of pore sizes, which may have been partially responsible for increasing K_fs and S. Additionally, in some burned soil samples, the increase in soil hydraulic properties may have been partially related to a concurrent reduction in “natural background” water repellency that is characteristic of dry, unburned soils in the Western Cascades. We observed no evidence of spatial autocorrelation in K_fs using semivariogram analysis. Principal component analysis paired with a k-means cluster analysis suggested that soil physical properties explained variations in soil hydraulic properties better than landscape attributes. Although there is a lack of regional results for comparison, our results trend in the opposite direction from drier, lower net primary productivity regions that are typically studied for post-wildfire soil hydraulic properties.

Hydrogeologic framework and conceptual groundwater-flow model of the panhandle and northwest parts of the High Plains (Ogallala) aquifer in Oklahoma, 1998–2022

Mon, 11 May 2026 17:07:27

This study was conducted by the U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board, to update the hydrogeologic framework and conceptual flow model for the panhandle and northwest parts of the High Plains (Ogallala) aquifer in Oklahoma, which together compose the Ogallala aquifer focus area. The study included the construction of a potentiometric surface, and available geologic and hydrologic data were used to evaluate saturated thickness of the aquifer. The water budget for the updated conceptual groundwater-flow model was based on estimated inflows and outflows for the 1998–2022 study period.

Saturated thickness of the Ogallala aquifer averaged 127 and 116 feet for the panhandle and northwest parts, respectively. Groundwater withdrawals from the Ogallala aquifer for 1998–2022 averaged 422,054 and 39,645 acre-feet per year (acre-ft/yr) for the panhandle and northwest parts, respectively. Recharge, the primary inflow, was estimated at 0.63 inch per year for the 1998–2022 study period, with the panhandle part of the Ogallala aquifer receiving 175,068 acre-ft/yr and the northwest part of the Ogallala aquifer receiving 49,376 acre-ft/yr. Additional inflows included irrigation return flows, estimated at 8,111 and 642 acre-ft/yr for the panhandle and northwest parts, respectively, of the Ogallala aquifer. Net lateral groundwater flows, considered to be aquifer outflows, were estimated to account for 31,908 acre-ft/yr for the Ogallala aquifer focus area. Streambed seepage, which was an outflow of 5,535 acre-ft/yr, was only present in the northwest part of the Ogallala aquifer. Vertical leakage and saturated-zone evapotranspiration were considered negligible outflows. These findings provide a revised conceptual groundwater-flow model water budget for the Ogallala aquifer focus area in Oklahoma.

Hazard potential of compound flooding from rainfall, storm surge, and groundwater in coastal New York and Connecticut

Mon, 11 May 2026 15:47:26

Compound flood events, the co-occurrence of multiple flood drivers, can result in flood hazard potential exceeding that of any single driver alone. To evaluate compound flooding in a semi-urbanized coastal area, historical records dating back to 1970 are used to study the co-occurrences of high precipitation, storm surge, and shallow groundwater conditions along the coastlines of New York and Connecticut. Joint return periods for coincident precipitation-surge events were computed using statistical dependence models and compared to the assumption of independence as a ratio, referred to here as a return period adjustment. Results indicate distinct seasonality where compound events in the area disproportionately occur in the cold season between October and April. Return period adjustments range from a factor of 1 to almost 9, demonstrating the range in precipitation-storm surge dependence across the study area. Across all 24 station triad locations, groundwater levels were elevated during times of precipitation- surge co-occurrence, reflecting the tendency for coastal storms and shallow groundwater conditions to co-occur seasonally. The result is a pseudo-trivariate compound flood hazard score and corresponding hazard map that integrates dependence between daily precipitation-surge events and overall monthly groundwater levels (as a precondition) into a relative compound hazard score. The location with the highest compound flood hazard score is on the south shore of Long Island, as well as locations across coastal Connecticut where groundwater levels compound the co-occurrence of heavy precipitation and storm surge.

Refinement of a framework for Moving Aircraft River Velocimetry (MARV) and application to particle tracking along Alaskan rivers

Legleiter, Carl; Kinzel, Paul; Laker, Mark; Conaway, Jeff — Tue, 12 May 2026 13:47:57

Information on river velocities enhances understanding flood hazards, evaluating habitat conditions, and predicting the transport of floating materials. In this follow-up study, we used data from two new sites, one with a more complex morphology and the other with a lower suspended sediment concentration, to provide further evidence that Moving Aircraft River Velocimetry (MARV) can yield accurate velocity estimates ( R² up to 0.87 when compared to field measurements) for long segments of large, turbid rivers. The MARV workflow is packaged in freely available software and is robust to implementation details; neither buffering to mitigate edge effects nor a new approach to aggregating velocity vectors improved performance. MARV was not sensitive to parameters used to establish overlapping image sequences, but combining a long window with a short jump between consecutive windows was the optimal configuration. Although accuracy varied from one cross section to the next, agreement between remotely sensed velocities and those measured in the field was independent of position within a frame range. As an initial step toward application of the approach to help address practical problems, we showed how MARV can drive particle tracking models. Our first-order simulations suggest that channel morphology and flow velocity are the primary controls on travel time and particle fate, with diffusive processes playing a lesser role. Although MARV can be used to characterize an instantaneous flow field, a more comprehensive framework that accounts for other physical processes would be required to model specific types of events like oil spills.

Simulation of groundwater flow to evaluate hydrogeologic controls on a PFAS plume, Coakley Landfill Superfund site, Rockingham County, New Hampshire

Harte, Philip; Collins, Andrew — Mon, 11 May 2026 20:03:08

Per- and polyfluoroalkyl substances (PFAS), including perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), have been detected at combined concentrations above 2,000 nanograms per liter (ng/L) at groundwater seep locations near the Coakley Landfill Superfund site, in North Hampton, New Hampshire. The landfill was active from 1972 to 1985. An impermeable cap was placed on the landfill in 1998. The adjacent area to the Coakley Landfill has many water supply wells, and transport of PFAS compounds to the wells is a concern. Fracture anisotropy in the underlying bedrock aquifer complicates the understanding of PFAS transport because groundwater preferentially travels along fractures that may not align with the prevailing groundwater flow direction.

In 2018, the U.S. Environmental Protection Agency and the U.S. Geological Survey began an investigation of the groundwater flow from the Coakley Landfill site. This report describes the modification of a numerical groundwater-flow model for the local area around the Coakley Landfill and summarizes findings of the investigation. In addition, this report includes a brief description of PFOA and PFOS occurrence, a discussion of model construction, evaluation of model performance through calibration, and discussion of simulation results for two periods (before and after capping). Limitations are also discussed.

Results show that simulated groundwater flow moves from the Coakley Landfill to the west and north. Advective transport modeling using particle tracking shows that groundwater from the landfill discharges primarily to streams to the west and north, and a small amount is transported to distal wells. Dilution of contaminants through advection and dispersion likely plays a role in whether PFAS compounds from the landfill will be detected above laboratory reporting levels at distal wells.

Landscape connectivity and wildlife access to water across an international border: Barriers and opportunities for facilitating transboundary movement

Tue, 19 May 2026 13:56:31

Rapid global acceleration in the construction of physical barriers along international borders has greatly influenced biodiversity and animal movement. Physical barriers can fragment landscapes, hinder access to essential resources, impact long-distance migrations, and inhibit dispersal and gene flow. The effects of physical barriers on animal movement and landscape connectivity can be exacerbated in dryland environments where access to water is a limiting factor. In recent decades, the construction of border barrier infrastructure has accelerated along the international boundary between the United States and Mexico. Here, we used a landscape connectivity model to investigate the effects of barriers on wildlife access to the river in the Lower Rio Grande Valley. We used a modified omnidirectional connectivity model to compare access to the river for three large, terrestrial mammal species across three border barrier scenarios: (1) a landscape without border barriers; (2) a landscape with the existing barrier system; and (3) a potential future landscape with a continuous barrier system. The existing barrier system includes many discrete sections of barrier within tracts of the Lower Rio Grande Valley National Wildlife Refuge or on lands associated with the region's flood control system. Our results indicate that the existing border barriers can impede connectivity and wildlife access to the river in some areas, while some existing gaps between border barrier sections can serve as conduits for wildlife movement and river access. Our future scenario results show how a potential continuous border barrier system could further impede wildlife access to the river. We discuss management and landscape conservation options for enhancing wildlife access to water and riverine habitats. Collectively, our results illustrate the potential effects of border barriers on wildlife movement and access to water, providing information that can be used to better anticipate and lessen the ecological impacts of transboundary barriers.

Regression models for estimating suspended sediment concentrations and loads and comparison with acoustic surrogate model on the Snake River, Weiser, Idaho, 1977–2022

Kenworthy, Megan — Mon, 11 May 2026 17:06:06

The U.S. Geological Survey, in cooperation with Idaho Power, developed streamflow- based regression models to estimate suspended sediment concentration (SSC) and loads on the Snake River at Weiser, Idaho site (U.S. Geological Survey streamgage 13269000; hereafter referred to as “Snake at Weiser site”). This site sits upstream from the dams and reservoirs of the Hells Canyon Complex and the Hells Canyon National Recreation Area, where large sandbars along the Snake River that provide recreation and riparian habitat and host archaeological resources have declined since 1973. Analyses of samples from historical (1977- 2003) and modern (2017- 22) periods show that SSC has decreased over time, with median concentrations declining from 50 milligrams per liter (mg/L) to 28 mg/L. Mann- Kendall trend tests confirm statistically significant declines in total SSC and the fine and sand fractions of suspended sediment through the full period of record.

Regression models specific to each period outperformed models using the full dataset, suggesting changes in the sediment supply to this reach of the Snake River and highlighting the need for period- based approaches. Regression models for total SSC and fine sediment were more accurate than those for sand, which exhibited greater error and bias, likely reflecting a sand supply limited by upstream dams. The regression model for modern period total SSC and a previously developed acoustic surrogate model showed similar performance, indicating both methods are viable for estimating SSC and loads.

These findings help to better quantify suspended sediment concentrations and loads upstream of the Hells Canyon Complex and provide resource managers with tools to better quantify sediment loads affecting reservoir storage and the maintenance of sandbars in the Hells Canyon National Recreation Area.

Water use in Louisiana, 2020

Robinson, Angela — Mon, 11 May 2026 17:02:38

The U.S. Geological Survey (USGS), in cooperation with the Louisiana Department of Transportation and Development, collected water-withdrawal and water-use data from a 2020 inventory of water withdrawals in Louisiana. In 2020, approximately 8,700 million gallons per day (Mgal/d) of water was withdrawn from groundwater and surface-water sources in Louisiana, which represented a 0.22-percent decrease from 2015. Total groundwater withdrawals were about 1,900 Mgal/d, an increase of 7.1 percent from 2015, and total surface-water withdrawals were about 6,800 Mgal/d, a decrease of 2.1 percent from 2015 to 2020.

Total water withdrawals, in million gallons per day, in 2020 for the various categories of use were as follows: public supply, 720; industry, 2,100; power generation, 4,100; rural domestic, 39; livestock, 7.0; rice irrigation, 930; general irrigation, 250; and aquaculture, 590. From 2015 to 2020, Louisiana’s total withdrawals for public supply increased by 1.4 percent, industry decreased by 2.3 percent, power generation decreased by 4.9 percent, rural domestic decreased by 1.2 percent, livestock increased by 11 percent, rice irrigation increased by 13 percent, general irrigation increased by 12 percent, and aquaculture increased by 20 percent.

About 51 percent (approximately 960 Mgal/d) of all groundwater withdrawn was from the Chicot aquifer system and 24 percent (approximately 450 Mgal/d) was withdrawn from the Mississippi River alluvial aquifer. Since 2015, withdrawals from the Chicot aquifer system increased by 13 percent, and withdrawals from the Mississippi River alluvial aquifer increased by 18 percent. About 72 percent (4,900 Mgal/d) of all surface water withdrawn was from the Mississippi River main stem. This value represents a 1.1-percent decrease in withdrawals from 2015 to 2020.

All water-withdrawal and water-use data presented in this report should be considered estimates. Because of rounding, totals and percentages presented in the tables, figures, and text in the report may differ slightly from totals or percentages calculated individually.

Riverine pesticide trends in the United States: Assessing a decade of national-scale monitoring

Shoda, Megan; Breitmeyer, Sara; Hinman, Elise Danica; Stackpoole, Sarah — Mon, 11 May 2026 14:19:13

Pesticides in freshwater systems can compromise water availability by degrading water quality, with implications for human health and aquatic life. Despite recognition of the need for national-scale monitoring and analysis, few studies have documented long-term trends in surface water pesticide contamination across the US. This study addresses that need by analyzing temporal trends and acute and chronic benchmark exceedances for aquatic life and human health from 81 river sites sampled from 2013 to 2022 using an analytical method targeting 80 pesticides. The majority (79%) of single site and pesticide combinations had too few pesticide detections to estimate trends. When detections were more frequent, increasing trends in concentration were twice as common as decreasing trends. Increasing pesticide concentrations were common in primary drainages of the Mississippi River Basin. Aquatic life benchmarks were exceeded by 19 pesticides, and exceedances were geographically widespread, with both acute and chronic aquatic life benchmark exceedances at 62% of sites. The herbicides atrazine and metolachlor and the insecticide imidacloprid were identified as the greatest threats to surface water availability based on their trends and aquatic life benchmark exceedances. These findings demonstrate the need for continued monitoring and trend analysis, driver investigation, and management strategies to protect freshwater resources.

Los Planes watershed vegetation monitoring: Standard operating procedures

Wilson, Natalie R. — Mon, 11 May 2026 13:48:50

This is a description of survey procedures for short term vegetation monitoring at Natural Infrastructure in Dryland Stream (NIDS) structure sites and control sites a ranch in the Los Planes, La Paz, Baja California Sur. This study design was modified from USGS Short Term Vegetation Response Study (Wilson et al. 2021) with the goal to quantify changes in species abundance/cover, structure, and composition. The Society of Ecological Restoration identifies 3 major ecosystem attributes of importance when assessing restoration projects, such as the installation of NIDS (Society for Ecological Restoration International Science & Policy Working Group 2004; Ruiz-Jaen and Mitchell Aide 2005). These attributes are vegetation structure, diversity, and ecological processes. Our protocol can be used to directly quantify vegetation structure and diversity and by collecting data over several years we can indirectly assess the ecohydrological processes associated with NIDS (Norman, Lal, et al. 2022).

Natomas basin giant gartersnake annual monitoring report 2024

Fri, 8 May 2026 17:28:23

The giant gartersnake (Thamnophis gigas) is a semi aquatic snake endemic to the Central Valley of California. After losing 95 percent of its historic wetland habitat (Frayer and others, 1989), giant gartersnakes became state and federally listed as a threatened species (California Fish and Game Commission, 1971; U.S. Fish and Wildlife Service 1993, 1999). Continued monitoring of current populations and implementation of suggested management actions is necessary to recover the species. The Natomas basin in Sacramento, California, supports a population of giant gartersnakes persisting in restored marshes and rice agriculture. This annual report summarizes the giant gartersnake monitoring project for 2024, focusing on the apparent survival, abundance, density, and distribution of the giant gartersnakes and the connectivity of habitat throughout the Natomas basin. In 2024, 131 giant gartersnakes were captured 216 times at 44 sites by hand or trap. The catch-per-unit effort decreased from 2023 to 2024 but was similar to other years of the study. Estimates of occupancy increased between 2023 and 2024, although the trend of occupancy from 2011 through 2024 is still decreasing overall at a mean annual rate of 3 percent per year. Apparent survival was much higher at Betts-Kismat-Silva from 2018 to 2019 and from 2021 to 2022 than in other years, but this may be partly attributed to different sampling efforts over the years. Trapping effort was more consistent in the Sills tract, and apparent survival was slightly higher in later years (2022–23 and 2023–24). Giant gartersnake populations appeared to remain stable in 2024, but abundance, density, survival, and distribution is highly variable across different sites and years of the study. Continued monitoring of the populations would allow for better trend estimates over time and assessment of the effects of management activities. Giant gartersnake populations throughout the basin and on reserve lands would likely benefit from the following: (1) creating more managed marsh; (2) increasing the amount of emergent tule vegetation in existing marshes (for example, Cummings, Natomas Farms, and Lucich South); (3) continuing to flood existing marshes in early spring; (4) maintaining rice agriculture; and (5) continuing research into conservation actions that target the giant gartersnake, such as habitat and water management and translocation.

Assessment of undiscovered oil and gas resources in the Bossier Formation within the onshore United States and State waters of the Gulf Coast Region, 2025

Mon, 11 May 2026 17:00:49

Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 3 million barrels of oil and 343.5 trillion cubic feet of gas in reservoirs of the Bossier Formation within the onshore United States and State waters of the Gulf Coast region.

Inland recreational fisheries harvest far exceeds reported inland harvest in the United States

Thu, 7 May 2026 15:11:11

Recreational fisheries are important global contributors to food security, socio-cultural practices, and local and regional economies. However, inland recreational fisheries are often overlooked by policymakers due to a limited understanding of the magnitude of participation, harvest, and economic impact. Here, we used the U.S. Inland Creel and Angler Survey Catalog and catch and effort model (CreelCatch) and several assumptions to provide an initial estimate of the magnitude of total inland recreational fisheries harvest in the conterminous USA. The CreelCatch model projected fishing harvest across lakes, ponds, and reservoirs based on fishing effort, water body area, and regional effects. We estimated that recreational lake fisheries in the conterminous USA likely harvest 236,000–671,000 tonnes of fish per year, 17–48 times greater than total inland fisheries harvest reported to the United Nations. Inland recreational fisheries may warrant greater consideration for their contribution to national scale socioeconomics and impacts on fish stocks and ecosystems.

Drift and dispersion of silver carp (Hypophthalmichthys molitrix) eggs and larvae for hypothetical spawning scenarios in the Upper Mississippi River

LeRoy, Jessica; Loppnow, Grace; Jackson, P.; Lasher, G. — Thu, 7 May 2026 14:43:22

Invasive carp pose ecological and economic risks to North American freshwater systems. This study uses the Fluvial Egg Drift Simulator to model the drift of invasive silver carp (Hypophthalmichthys molitrix) eggs and larvae after hypothetical spawning in Pools 1–10 of the Upper Mississippi River. Although adult invasive carps have been detected in this region, no reproduction has been confirmed as of this publication. A total of 450 spawning scenarios were simulated, representing 5 water temperatures, 9 flows, and 10 spawning locations in the tailwaters of lock and dam structures. The study examined egg and larval positions at two key developmental stages: hatching and gas bladder inflation, when larvae seek nursery habitat. Under a wide variety of flow conditions and water temperatures, eggs spawned upstream from Lake Pepin (Pool 4) are likely to settle in the lake before hatching, possibly increasing mortality rates. Eggs that survive passage through Lake Pepin reach gas bladder inflation within the study area, except in scenarios with lower temperatures and higher flows. Conversely, larvae spawned downstream from Lake Pepin generally drift out of the study area before reaching gas bladder inflation, except in cases of higher temperatures and lower flows. These findings inform ichthyoplankton sampling strategies and management actions aimed at reducing invasive carp populations in areas likely to support recruitment.

Water scarcity and infrastructure risk of amplified seasonal sediment transport

Tue, 19 May 2026 14:28:32

Climate warming and deglaciation are reshaping hydrological seasonality in cold–dry regions, threatening the long-term sustainability of agriculture, ecosystems and local communities. However, existing evidence is limited to runoff seasonality. Changing sediment-transport seasonality, a more sensitive component, is emerging as a substantial yet under-recognized threat to water infrastructure. Leveraging monthly observations from the upper Tarim River from the 1960s to 2000s, we show that a warmer and wetter climate has intensified sediment-transport seasonality, with a 43% increase in summer sediment fluxes. Over half of this amplification stems from more frequent extreme sediment transport, particularly events triggered by high sediment supply rather than high discharge. Supported by a state-of-the-art river change dataset, we show that enhanced sediment seasonality and extreme sediment transport have largely contributed to increased river mobility since 2000. Sediment-driven changes are pushing riverine processes towards greater unpredictability and pose growing threats to water infrastructure and water security in vulnerable cold–dry regions.

Restoration in motion: Expanded migration and distribution of silver redhorse Moxostoma anisurum and shorthead redhorse M. macrolepidotum

Mon, 8 Jun 2026 13:16:07

Habitat fragmentation poses a significant threat to migratory species. Dams are a common form of fragmentation, and recent restoration efforts around the Great Lakes have prioritized dam removal. We used acoustic telemetry to describe migratory movements of two redhorse species in the Sandusky and Cuyahoga rivers, Ohio, USA in relationship to habitat reconnection. Shorthead redhorse (Moxostoma macrolepidotum) typically migrated from both rivers into Lake Erie between May and July, moving 40–248 km straight-line distance from the river before returning the following spring. We recorded individual cumulative distances up to 809 km between spawning seasons. Shorthead redhorse demonstrated tributary fidelity, but individuals from both rivers co-occurred along southern Lake Erie. Silver redhorse (M. anisurum) largely remained in their tagging tributary watersheds year-round. Cuyahoga River silver redhorse moved upstream from March to April 28.8 km on average and passed upstream of the historical Brecksville Dam (removed in 2020), occasionally reaching the next upstream dam. Telemetry data revealed redhorse use of newly available habitat upstream of dam removals and previously undescribed long-range adfluvial migration by shorthead redhorse.

Analysis of alternative weir designs for improved passage of select fish at the U.S. Geological Survey streamgaging weir at Blackwells Mills, New Jersey

Suro, Thomas; Niemoczynski, Michal; Mulligan, Kevin — Mon, 11 May 2026 16:59:37

As the population of New Jersey continues to remain dense, the need for water supply will likely continue to be high, which can lead to water managers needing to make difficult decisions about managing drinking-water supply. Streamgaging weirs like the ones used by the U.S. Geological Survey (USGS) play a critical role in providing accurate and stable streamflow data, but their presence can affect the passage of diadromous fish species such as river herring (Alosa pseudoharengus [alewife], Alosa aestivalis [blueback herring], and Alosa sapidissima [American shad]). In some situations, weirs existing in rivers and streams are no longer used because they were part of a farm irrigation system or some type of industrial operation. The weir at the USGS streamgage 01402000 Millstone River at Blackwells Mills, New Jersey, was purposefully built as a hydraulic-control structure that provides a precise and stable control for the measurement of stage and computation of continuous streamflow. To satisfy the dual need of maintaining accurate streamflow data and providing improved fish passage for select species of fish during migration season, the USGS proposed the development and evaluation of two alternative weir designs that would meet the criteria established for successful passage of American shad, alewife, and blueback herring during their yearly migration. The designs were also required to maintain adequate control of the upstream pool elevation necessary for the precise computation of streamflow used by State agencies for municipal water-supply purposes for surrounding communities.

Two alternative weir design modifications were incorporated at the center of the Blackwells Mills weir and modeled using two-dimensional hydraulic modeling software and three-dimensional computational fluid-dynamics software to simultaneously evaluate conditions for passage of the target fish species and effects to streamflow computations at the streamgage. The models were calibrated to existing conditions around the weir location using surveyed-elevation data and recorded stage, streamflow, and velocity in the Millstone River. The alternative weir designs lowered the weir crest by 1.02 feet (ft) and the resulting simulations showed an effective increase in depth of 0.98 ft at the median streamflow of 251 cubic feet per second (ft³/s) and 0.96 ft at the 95-percent exceedance streamflow of 98 ft³/s. The alternative weir designs were also found to increase streamflow depth across the shallowest portions of the weir structure at the downstream anti-scour skirt by lowering the skirt about 4 inches, allowing for two or more body depths of water for American shad, alewife, and blueback herring at the median migration streamflow of 251 ft³/s. The alternative weir designs also reduced the highest stream velocities across the downstream weir sill and anti-scour skirt from about 9 to 10 feet per second, and the depth-averaged velocity to about 7 to 8 feet per second. The sensitivity of the weir with respect to the computation of streamflow was increased from about 1.8 cubic feet per second per hundredth foot to 1.6 cubic feet per second per hundredth foot for streamflows of about 10–100 cubic feet per second.

Regional conservation planning tool: A spreadsheet model to support spatial prioritization and resource allocation decisions

Fri, 8 May 2026 14:24:23

Prioritization is a central component of natural resource management because conservation needs routinely exceed available resources. Waterfowl and wetland conservation programs in North America are at the forefront of landscape-scale prioritization and transboundary management decisions due to the migratory nature of ducks, geese, and swans. The growing availability of geographic information systems (GIS) and geospatial technologies has accelerated the development of multi-objective landscape prioritization models, including applications of structured decision making and multi-criteria decision analysis to spatial planning for waterfowl and wetlands at the continental scale. However, regional managers and conservationists could benefit from flexibility in downscaling continental tools, selecting objectives, and assigning weights for rapid production of spatial prioritization models at smaller spatial scales without extensive computer coding or GIS analysis. We developed a spatial value model that prioritizes landscapes at sub-continental scales (e.g., states and provinces, bird conservation regions, etc.) and provides flexibility for users to select waterfowl conservation objectives of interest and weights. Our model can be used for direct downscaling of an existing continental geospatial model or further customized with region-specific geospatial data. We illustrate how regional prioritization can vary with the spatial scale selected by the user. The spatial value modeling framework and the downscaling tool presented here could increase the use of multi-criteria decision analysis and linear value modeling in spatial landscape prioritization, while also providing flexibility for selecting scales, objectives, and weights. Our spreadsheet tool was developed specifically for use by regional biologists, conservationists, and managers and does not require knowledge of GIS software (although results can be exported from the spreadsheet for spatial analysis using GIS). Together, the model outputs and the accompanying spreadsheet tool provide a bridge between continental waterfowl conservation and regional implementation, enabling rapid, stakeholder-driven, value-explicit prioritization.

An automated geographic information system-based hydraulic modeling tool for developing preliminary culvert designs for stream crossings in Massachusetts

Fri, 1 May 2026 19:08:48

Introduction

Currently (2026), many of the about 25,000 roadway crossing structures over rivers and streams in Massachusetts are undersized. Undersized culverts and bridges can be detrimental to fish and wildlife movement, habitat continuity, and the health of aquatic organisms. Undersized culverts also can lack the resiliency needed to withstand large floods, which could be worsened by potential increases in flood magnitude and frequency due to climate change. Improving culvert and bridge designs for stream crossing projects may improve aquatic organism passage, stream continuity, and resiliency during future floods by decreasing upstream overbank flooding, road flooding and erosion, and degradation of aquatic habitat.

The U.S. Geological Survey (USGS), Massachusetts Department of Environmental Protection (MassDEP), and University of Massachusetts Amherst began a series of cooperative studies in July 2019 to develop an automated geographic information system (GIS) hydraulic modeling tool for preliminary culvert designs for stream crossings. The USGS plans to provide preliminary culvert designs in the web-based StreamStats application, which enables municipalities and engineers to view potential designs and related information for stream crossing replacement projects in Massachusetts. This application can (a) provide information on hydrology, hydraulics, and ecological conditions at stream crossing sites, (b) provide users with potential culvert designs to improve aquatic organism passage and flood resiliency, and (c) assist MassDEP in implementing the Massachusetts Wetlands Protection Act regulations for stream crossing projects.

Informing policy response to declining water supply in the Colorado River basin: Linking water supply management with outcomes for fish communities

Schmidt, John; Yackulic, Charles — Wed, 20 May 2026 16:45:06

Water-supply managers in the Colorado River Basin are tasked with balancing consumptive water use with natural water supply. Decisions associated with water-supply policy can include where and how much water consumption occurs, where water could be stored, and how to operate reservoirs. Water-supply decisions often affect other resources including energy production, recreation and aquatic ecosystems.

The goal of this project was to model how different water supply management scenarios might affect riverine ecosystems with a specific focus on potential impacts on federally listed fish populations, including threatened humpback chub (Gila cypha) and endangered Colorado pikeminnow (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus). Threats to these endemic species include introduced non-native fish species that often become invasive, like smallmouth bass (Micropterus dolomieu), and altered physical conditions that may favor these non-native fish species over the endemic fish species. Changes in how water supply may be managed in the Colorado River Basin can affect physical conditions in rivers by altering how much water flows through a particular river segment at a given time, by changing the extent of riverine ecosystems between reservoirs, and by determining the quality of water released from storage reservoirs with fixed release elevation (e.g., full reservoirs generally release colder water). To address our goal, we developed tools that coupled water storage models, river temperature models and fish population models to examine how different scenarios to operate Lake Mead, Lake Powell, and Flaming Gorge Reservoir, the three largest reservoirs in the watershed, may affect fish populations.

We developed our work plan when available water supply was diminished. At the end of our project period (May 2022), Lake Powell and Lake Mead contained historically low water levels, and our models were being used in evaluating different options for operating Lake Powell by the Bureau of Reclamation and other stakeholders.

Geochemical geodatabase of sedimentary strata (coal, coal-adjacent rocks, tuffaceous oil shale, phosphate-rich rocks) and produced water in the Uinta region, Utah and Colorado

Thu, 28 May 2026 14:50:26

The Geochemical Geodatabase of Sedimentary Strata (Coal, Coal-adjacent Rocks, Tuffaceous Oil Shale, Phosphate-rich Rocks) and Produced Water in the Uinta Region, Utah and Colorado, consists of compiled datasets acquired as part of the Carbon Ore, Rare Earth, and Critical Mineral (CORE-CM) Uinta Region assessment funded by the U.S. Department of Energy (DEFE0032046, 2021–2024; Birgenheier et al., 2024). The CORE-CM assessment focused on providing comprehensive geological and geochemical characterization of current and prospective sedimentary-hosted resources including coal, oil shale, phosphatic limestone, and produced water from oil and gas targets present in eastern Utah and northwestern Colorado (Figure 1).

This Data Series includes a geodatabase that consists of analytical geochemical data collected September 2021 through December 2024 via portable X-ray fluorescence (pXRF), and laboratory measured analyses produced by inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The coal-related geochemical data are derived primarily from the Cretaceous Blackhawk Formation and Ferron Sandstone of Utah, and the Mesaverde Group of Colorado. Additional non-coal resources assessed include oil shale-bearing strata of the Eocene upper Green River Formation (Utah and Colorado), phosphate-rich limestone of the Permian Park City Formation (Utah) and produced water from oil and gas-bearing strata of the Eocene Green River and Wasatch Formations (Uinta Basin) and the Pennsylvanian Paradox Formation (Paradox Basin) (Table 1). The CORE-CM assessment included a wide range of lithologies present in the coal, oil shale, and phosphate geologic resource systems whether or not the specific lithology has current economic value. Geochemical analyses of produced water from oil and gas wells focused on current and emerging hydrocarbon targets in the central Uinta Basin and northern Paradox Basin. A total of 13,092 geochemical analyses from these geologic systems is provided in the included geodatabase. A series of coal quality data (e.g., composition and maceral analyses) is also included in the database and was digitized from archived coal samples from the Utah Geological Survey (Appendix A).

Science for drought response

Wilson, Tamara; McAfee, Stephanie — Mon, 1 Jun 2026 14:38:14

Droughts impact water availability and quality, agriculture, energy production, ecosystem health, cultural resources, and wildfire risk. In an average year, nearly 15% of the US experiences significant drought, and in some recent years, drought conditions have impacted more than a third of the nation (U.S. Drought Monitor).

The U.S. Geological Survey (USGS) Climate Adaptation Science Centers (CASCs) deliver actionable science to help land and resource managers prepare for, reduce the risk of, and recover from drought.

Understanding the occurrence and distribution of per- and polyfluoroalkyl substances (PFAS) in surface waters of the nontidal Passaic River Basin

Fri, 1 May 2026 16:47:30

This study, completed by the U.S. Geological Survey in cooperation with the North Jersey District Water Supply Commission (NJDWSC), was designed to characterize the occurrence and distribution of per- and polyfluoroalkyl substances (PFAS) in surface waters of the nontidal Passaic River Basin in New Jersey that have the potential to affect public-drinking-water quality. In 2025, 37 sites in the Wanaque, Ramapo, Pompton, and Passaic River watersheds were sampled in January, March, July, and September under base-flow conditions and a subset of sites was sampled during two rain events. Samples were analyzed for 40 individual PFAS and total organic carbon and a subset of samples was analyzed for 1,4-dioxane and trace elements. Fifteen PFAS were detected at least once, with individual concentrations ranging from 0.42 to 28 nanograms per liter (ng/L; median, 2.8 ng/L). Perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) were widespread and detected in 100 and 97 percent of the samples, respectively. Concentrations of PFOA and PFOS ranged from 1.2 to 28 ng/L (median, 7.7 ng/L) and from 0.52 to 12 ng/L (median, 3.8 ng/L), respectively. Generally, concentrations were lower in the Wanaque and Ramapo River watersheds compared to the Pompton and Passaic River watersheds. Concentrations of PFOA and PFOS were highest in July and September when flows were low. During rain events, median concentrations of PFOS were elevated compared to those observed under base-flow conditions, indicating potential inputs from non-point sources. To understand potential drivers of PFAS concentrations, land cover and potential PFAS sources were summarized for each sampling site, and an accumulated wastewater model was used to estimate the percentage of wastewater from upstream municipal and industrial sources in all flowlines of the Passaic River Basin. Developed land, the number of potential sources, and the mean-annual accumulated wastewater percentage were highly correlated with PFAS concentrations and Deciduous Forests were negatively related to concentrations. Data provided by this study can be used by water purveyors and resource managers to make treatment and mitigation decisions to minimize PFAS in local surface waters used as drinking-water resources.

Assessment of long-term trends in streamflow statistics within and near the Mobile Bay and Perdido Bay watersheds, United States, 1950–2022

Asquith, William; Crowley-Ornelas, Elena; Whaling, Amanda — Fri, 1 May 2026 16:45:34

The U.S. Geological Survey, in cooperation with the Gulf Coast Ecosystem Restoration Council, assessed monotonic trends for a variety of streamflow statistics for 69 long-term U.S. Geological Survey streamgages within either the Mobile Bay or Perdido Bay watersheds that were active through at least at the end of calendar year 2019. Long-term data were defined for this investigation as having at least 50 years of cumulative record within the period since January 1, 1950, with a requirement for a complete record of streamflow during the 2010s (2010–19). The 69 streamgages have at least 54 years and as many as 73 years of daily mean streamflow data; the median period of record is 72 years; and 15 of the streamgages are identified as “major nodes” on the basis of the criteria described. The occurrence of statistically monotonic significant trends for the 69 streamgages at the 0.05 significance level is spatially shown for six statistics. For the major node streamgages, the study depicts (1) time-series graphics of annual mean, annual harmonic mean, decadal 10th, 50th, and 90th-percentile streamflows, and (2) a variation on Quantile-Kendall plots of Kendall’s tau and streamflow nonexceedance probabilities for each of the 365 days of a year. Trend assessment synthesis shows that, except for a few streamgages with relatively greater counts of statistically significant trends than others, the majority (about 93 percent) of individual trend tests indicate no trend in the streamflow and ecological metrics considered.

Evaluating approximations of river channel shape using a national cross section database

Legleiter, Carl; Kinzel, Paul — Fri, 1 May 2026 14:00:47

Many hydrologic applications require basic information on the size and shape of river channels, but measuring cross section (XS) geometry in the field or via remote sensing can be costly and often provides only partial coverage. Given these challenges, we capitalized upon an existing data set of 46,971 XS from gaging stations to evaluate various approximations of channel shape. After screening and pre-processing these data, we fit four model types to each XS, including a new approach that involves Stacking PDFs (probability density functions) to Approximate River Channel Shapes (SPARCS). This framework produced depth estimates that closely matched field measurements, with typical cross-sectional area errors <1% and a median R² of 0.77 for comparison of observed and predicted depths. SPARCS model parameters can be interpreted in terms of channel characteristics: mean depth, asymmetry, bar convexity, and flatness of the bed. The model performed well for the XS included in the database, which was biased toward straight, uniform channels conducive to operational streamflow measurement. Neither model parameters nor accuracy were dependent on discharge. We also assessed the potential of SPARCS to fill in measurement gaps and found that although the model can help, the accuracy of inferred depths decreased as the observable fraction of the channel decreased. An important limitation of SPARCS is that mid-channel bars or multi-threaded morphologies cannot be produced. Graphical tools can help visualize how model parameters affect simulated river forms. SPARCS could facilitate satellite-based discharge estimation by providing prior information on channel shape.

Changes in suspended sediment concentration along tidal rivers of the Chesapeake Bay: The tidal freshwater “sediment shadow”

Noe, Gregory; Murphy, Rebecca; Krauss, Ken — Fri, 15 May 2026 13:15:07

Transport of terrigenic sediment from nontidal watersheds into estuaries has important impacts on coastal habitat quality, pollutant transport, and resilience to sea-level rise. However, relatively little is known about changes in suspended sediment as nontidal rivers encounter tide, transition into tidal rivers through the tidal freshwater zone (TFZ), and enter saline portions of estuaries. The goal of this paper is to identify spatial and temporal patterns in suspended sediment concentration (SS) changes across tidal and salinity gradients over multiple tidal rivers, using a robust monitoring long-term dataset from the Chesapeake Bay. The multiple TFZs in the Chesapeake Bay consistently have a “sediment shadow” shown by a local spatial minimum in SS compared to upstream nontidal and downgradient oligohaline river reaches. Similarly, freshwater inputs from nontidal rivers have diminishing influence on tidal SS temporal dynamics with distance downstream from the head-of-tide. Therefore, little of the contemporary watershed sediment load is likely transported past the TFZ except during extreme floods when some sediment may be delivered to saline portions of the estuary. Tidal freshwater and brackish portions of the estuary have spatially variable trends in SS over time, both increases and decreases. However, the more saline downstream ends of tidal rivers and the mainstem of the Chesapeake Bay have had a consistent average 25% decline in SS over the past decades. In summary, the presence of “sediment shadows” suggests watershed loads of sediment are currently mostly not transported through the TFZ into the saline estuary, and likely generate sediment deficits for tidal freshwater wetlands.

Geospatial assessment of agrivoltaic opportunities and land use requirements in Nigeria

Tue, 9 Jun 2026 15:28:29

Agrivoltaics, the co-location of agriculture and solar photovoltaic (PV) infrastructure, can deliver co-benefits like reduced plant drought stress and improved yields of shade-tolerant crops, particularly in water-scarce regions. Despite growing global interest, the technical potential and opportunities for agrivoltaics remain poorly understood in many regions facing both food and energy insecurity, such as sub-Saharan Africa. Here we provide a spatial assessment of agrivoltaic opportunities in Nigeria by integrating cropland distribution, solar resources, and water stress. We find that northern states—where cropland is abundant and water-stressed, solar irradiance is high, and electricity access remains low—offer the greatest potential for agrivoltaic systems to generate co-benefits. In contrast, the humid forest regions of southern Nigeria exhibit lower suitability, with sparse cropland and weaker solar potential. We also estimate that northern states could fully meet their projected 2050 solar energy targets by allocating less than 1% of existing cropland to agrivoltaics, whereas southern states would require much larger fractions (5.9–18.9%). Notably, in the northern state of Kano, the country’s most populous, allocating 0.6–1.8% of cropland would be sufficient to meet mid-century solar energy projections. Collectively, our findings highlight priority regions where agrivoltaics could most effectively strengthen food-energy security linkages and support equitable energy transition in Nigeria.

Habitat and landscape variables affecting Corbicula fluminea presence in the upper Savannah River drainage (USA)

Tue, 9 Jun 2026 14:57:03

Aquatic invasive species (AIS) are amongst the greatest threats to native aquatic biodiversity. These introduced species often thrive in human-altered environments and spread through human-mediated pathways to invade new watersheds. Corbicula fluminea is a freshwater bivalve native to southeastern Asia first introduced in North America in Seattle, WA, in 1938 and has spread to nearly every major watershed in the southeastern United States. In the present study, we use an information theoretic framework to compare landscape and stream habitat variables associated with C. fluminea presence across five HUC10 watersheds in the upper Savannah River basin of South Carolina and Georgia, USA. Predictive models included landscape-level and site-level habitat variables associated with agricultural, developed, and forested landscapes. Models with variables associated with forested and developed landscapes were the top performing models based on AICc values. In top performing models C. fluminea presence was positively correlated with increased stream width, but negatively correlated with substrates dominated by cobble. Lower performing models highlight positive correlations with the presence of upstream reservoirs and increased developed landscape surrounding the site. Identification of habitat and landscape correlates with invasive species presence may lead to more efficient introduction monitoring efforts for conservation managers.

Hydrologic investigation of water level fluctuations at Moreau Lake, Moreau Lake State Park, town of Moreau, New York

Heisig, Paul M. — Fri, 1 May 2026 16:44:17

The causes of water level fluctuations at Moreau Lake, within Moreau Lake State Park in the town of Moreau, New York, were investigated from 2016 to 2021 after lake water levels dropped between 2015 and 2016, raising concerns about the loss of a shallow swimming area at the park beach. Annual variation in precipitation records from the area did not account for the lake water level decline. Two possible causes for the low lake water levels were investigated: the increase in groundwater withdrawals from new residential development since about 2000 and seasonal changes (nongrowing and growing seasons) in precipitation.

Investigation of the potential effects of nearby groundwater withdrawals required the compilation and collection of well-log data, seismic surveys, and measurements of lake and groundwater levels, field chemical parameters, and water isotopes to define the hydrogeologic system and to estimate water use. The net result of this work was the determination that Moreau Lake is a “flow though” lake with no surface water outlet; groundwater enters the lake on the upgradient side and exits through the downgradient side, however, groundwater does not flow southward from the lake toward nearby groundwater withdrawals from the semiconfined aquifer, and thus groundwater withdrawals were unlikely to have an effect on lake water levels.

Investigation of the historic precipitation records during nongrowing (November through April) and growing (May through October) indicated that (1) nongrowing season precipitation from 2011–12 to 2015–16 was more deficient than any similar period during the past 78 years and (2) since about 2000, nongrowing seasons have been drier overall and growing seasons have been considerably wetter. Initiation of lake water level monitoring in 2016 provided an opportunity to compare seasonal precipitation with seasonal lake water level changes. Nongrowing season lake water levels are very sensitive to precipitation, such that high precipitation (40 percent above the seasonal median) resulted in a 5-foot rise in lake water level. In contrast, the growing season lake water levels are sensitive to dry conditions; for example, deficient rainfall (about 6 percent below the seasonal median) resulted in a decline of lake water levels of about 3.5 feet. However, lake water levels are insensitive to high growing season rainfall inputs (about 10 to 47 percent above the seasonal median); lake water levels consistently declined about by 0.8 feet above this range of seasonal excessive precipitation.

Shallow hydrogeologic framework of the Tully Valley mudboil area, Onondaga County, New York

Fri, 1 May 2026 16:42:15

Mudboils have been documented in the Tully Valley in southern Onondaga County, New York, since the late 1890s. Sediment-laden water from the mudboils flows into Onondaga Creek, which empties into Onondaga Lake at Syracuse 15 miles to the north. Turbidity from the mudboils has degraded the water quality of Onondaga Creek despite a series of mitigation efforts that began in the early 1990s. Turbidity mitigation actions presently (2025) being considered include creek relocation and offline sediment settling. In support of these proposed actions during 2021–23, the U.S. Geological Survey, in cooperation with the New York State Department of Environmental Conservation, U.S. Environmental Protection Agency, Onondaga Nation, Onondaga Environmental Institute, and Central New York Regional Planning and Development Board, collected and analyzed geologic, hydrologic, geophysical, and geotechnical data to characterize the shallow hydrogeology along four proposed creek-relocation paths and in the proposed offline settling basin area.

The investigation indicated that the four proposed creek-relocation paths, two east of Onondaga Creek and two west of Onondaga Creek, are underlain by sediments including muck, alluvium, mudboil deposits, alluvial-fan sand and gravel, and lacustrine fines. The proposed excavations would penetrate partially to fully saturated conditions: generally, the water table is shallow near the creek and deep on the alluvial fans. The shallowest excavation, about 5 feet below land surface, would be near the creek and primarily in alluvium, and the deepest excavation, as much as 30 feet below land surface, would be in the alluvial-fan deposits. Brackish waters would be penetrated by proposed channel excavations on the eastern side of Onondaga Creek in an area downgradient from a potentially leaking historical salt-exploration borehole and near the main mudboil area. Excavation in these areas likely would provide a continuous source of brackish groundwater to the relocated creek. Proposed channel excavations of muck, soft to very soft lacustrine fines, and mudboil-type sediments in mudboil and suspected mudboil areas would pose an excavation and slope stability challenge and would have the greatest potential to create new mudboils. Proposed channel excavations below the water table on the Rattlesnake Gulf and Rainbow Creek alluvial fans would intercept groundwater and make the constructed streambank susceptible to seepage-induced slope instability. The substantial water-level fluctuation in the sediments of both alluvial fans would aggravate the stability condition. In addition, excavation on the Rattlesnake Gulf alluvial fan would have the potential to affect water-supply springs at the toe of the fan.

The proposed offline settling basin area is in the northern part of the Rattlesnake Gulf alluvial fan. Natural and man-made diversions of Rattlesnake Gulf have resulted in saturated conditions in the general area of the proposed basin. The proposed offline settling basin would be excavated in, and berms would be constructed on, alluvial-fan deposits and lacustrine fines. In the proposed basin area, the alluvial deposits overlying the lacustrine fines are less than 10 feet thick. Excavation, berm construction, and loading of the saturated, soft to very soft lacustrine fines may be problematic and require soil strengthening.

Characterizing the long-term (1981–2023) temperature and precipitation dynamics in the Trans-Mountain regions of Kazakhstan, Central Asia

Wed, 29 Apr 2026 14:27:38

Mountain regions are highly climate-sensitive, yet long-term observational evidence of elevation and seasonal climate dynamics in Central Asia remains limited. This study examines spatiotemporal trends in temperature (Tmean, Tmax, Tmin, and diurnal temperature range [DTR]) and precipitation across Kazakhstan’s transmountain regions using 74 meteorological stations (1981–2023). Data were analyzed using the Mann–Kendall test and Sen’s slope estimator, stratified across six elevation zones from lowlands (<400 m) to high mountains (>1500 m). Results reveal a robust, spatially coherent warming signal across all zones. Annual Tmean increased at a median rate of ~0.30 °C decade⁻¹, peaking at 0.36 °C decade⁻¹ above 1500 m, corresponding to an absolute increase exceeding 1.5 °C. Warming exhibited strong seasonal and diurnal asymmetries. Spring warmed most rapidly, with Tmean increasing >0.60 °C decade⁻¹ (approaching 3 °C total). Winter warming was driven by Tmin increases (up to 0.44 °C decade⁻¹), causing widespread DTR contraction, whereas summer warming was driven by Tmax increases, expanding DTR at higher elevations. Tmin showed the strongest elevation amplification overall. In stark contrast, precipitation trends were weak, spatially heterogeneous, and largely non-significant. Annual changes ranged from −6.63 to +14.35 mm decade⁻¹, with seasonal tendencies indicating modest, non-significant winter/spring wetting and summer drying. Ultimately, the results demonstrate a profound decoupling between strong, elevation-dependent warming and weak precipitation changes. The acute amplification of temperature, particularly during spring and summer at high elevations, has severe implications for snowmelt timing, glacier mass balance, evapotranspiration demand, and long-term water security in Kazakhstan.

Peak-, mean-, and low-streamflow regional-regression equations for natural streamflow in central and western Colorado, 2019

Kohn, Michael; Mast, M.; Gross, Tara — Mon, 18 May 2026 16:07:47

The U.S. Geological Survey (USGS), in cooperation with the Colorado Department of Transportation, developed peak-, mean-, and low-streamflow regional-regression equations for estimating various statistics for natural streamflow in hydrologic regions of central and western Colorado. The peak-streamflow regression equations were developed using data from 418 streamgages, consisting of 15,202 years of record and a mean of approximately 36 years of record per streamgage. The mean- and low-streamflow regional-regression equations were developed using data from 323 streamgages where daily streamflow data were collected year-round. The annual exceedance-probability discharges for each streamgage were computed using the USGS software program PeakFQ. Mean monthly and 7-day minimum and maximum streamflows were computed using the USGS software program SWToolbox. Streamflow-duration values were computed using an R script. The regional-regression equations were determined using data for the period of record for a given streamgage through water year 2019. Geographic information systems datasets were used to develop 55 basin and 42 climatic characteristics, which were evaluated as candidate explanatory variables in the regression analysis.

For the peak-streamflow regional-regression equations, the study area was divided into four hydrologic regions based on mean basin elevation, including the Plateau (less than 8,014 feet), Mid-Elevation (8,015 feet to 9,492 feet), Sub-Alpine (9,493 feet to 10,490 feet), and Alpine (greater than 10,490 feet) regions. For the peak-streamflow equations, the selection of basin and climatic characteristics was based on the 1-percent annual exceedance-probability discharge for each hydrologic region.

For the mean streamflow, streamflow-duration values, and 7-day minimum and maximum streamflows, the study area was divided into four hydrologic regions based on river basin, including the (1) Colorado-East Slope Headwaters, (2) Green River, (3) Rio Grande, and (4) San Juan-Dolores. For mean streamflows, basin and climatic characteristics were evaluated separately for the annual period and each month for each hydrologic region. Regional regression equations published in this report are available for use in the USGS web-based program StreamStats.

Cyanobacterial bloom occurrence and emergency department visits for asthma or wheeze, Wisconsin, 2017–2019

Thu, 7 May 2026 15:56:42

Background:

Cyanobacterial harmful algal blooms (cyanoHABs) pose risks to human and animal health.

Methods:

We investigated the relationship between cyanoHABs and asthma or wheeze-related emergency department (ED) visits near three Wisconsin cities (Green Bay, Madison, and Oshkosh) during 2017–2019. CyanoHAB exposure was approximated using the Cyanobacterial Assessment Network remotely sensed satellite indicator of cyanobacterial biomass, a chlorophyl algorithm (Chl_BS) aggregated by water-adjacent ZIP Code Tabulation Areas (ZCTA), and distance weighted from the nearest waterbody. Weekly counts of ED visits for asthma or wheeze were aggregated by ZCTA. Poisson generalized linear models estimated the association between the weekly number of ED visits and weekly Chl_BS, adjusting for maximum temperature, dewpoint, fine particulate matter (PM_2.5), month, and correlation within ZCTA.

Results:

During 2017–2019, 7,057 ED visits for asthma or wheeze occurred in the study area (42 ZCTAs). Peaks in Chl_BS occurred between June and October, with higher values in Lake Winnebago and Lake Mendota compared to Green Bay. Chl_BS was not associated with ED visits for asthma or wheeze (adjusted rate ratio = 1.00, 95% confidence interval = 0.99, 1.00), and the presence of onshore winds did not change this result. Monthly aggregations of ED visits and Chl_BS showed a monotonic trend between increasing Chl_BS and ED visits during July–September.

Conclusion:

This study demonstrates the utility of remote sensing data in environmental health research. Future studies could explore individual-level exposure and outcomes to refine health risks associated with cyanoHABs.

Spatially consistent but temporally divergent changes in nitrate and phosphorus loads and yields in Illinois watersheds, 1997–2022

Wed, 29 Apr 2026 15:01:54

Illinois contributes substantial nutrient loads to the Gulf of America, warranting watershed-scale assessment. This study estimated nitrate-nitrogen (nitrate-N) and total phosphorus (TP) loads and yields for 49 Illinois 8-digit hydrologic unit code (HUC8) watersheds draining to the Mississippi River Basin from 1997–2022, comparing recent (2018–2022) to baseline (1997–2011) conditions. Estimates included point and nonpoint source contributions, dissolved phosphorus, and water yields. During the recent period, nonpoint sources dominated nutrient export (82% nitrate-N, 78% TP), though point sources drove high yields in the Chicago area. Spatially, nonpoint source nutrient hotspots persisted with nitrate-N yields highest in east-central and northern Illinois and TP yields higher in southern and western Illinois. Temporally, statewide nitrate-N loads decreased 9%, while TP loads increased 27%. Nitrate-N yields increased in 22 HUC8s and decreased in 20, while TP yields increased in 32 HUC8s and decreased in 9. For both nutrients, baseline yields were negatively correlated with yield changes, indicating high-yielding watersheds tended toward larger decreases or smaller increases. Water yields increased 19% on average but were weakly correlated with nutrient yield changes (r = 0.23 and 0.20 for nitrate-N and TP). These results reveal spatially persistent yet temporally divergent nutrient export across Illinois, with contrasting nitrate-N and TP trajectories for nonpoint sources.

Standardized method for logging drill core at the Idaho National Laboratory, Idaho

Dietz, Haley — Tue, 21 Apr 2026 14:52:03

The U.S. Geological Survey’s (USGS) Lithologic Core Storage Library (CSL) at the Idaho National Laboratory stores more than 120,000 feet of drill core that is accessible to the public for research and sampling. To effectively convey the physical and descriptive properties of the drill core, USGS staff at the Idaho National Laboratory Project Office log the drill core and publish the lithologic logs as data releases. The logs provide essential data on the lithology, texture, mineralogy, alteration, and other physical properties of the core, which serve as valuable information for researchers to guide their research and sampling efforts. To ensure consistent, quality, and dependable lithologic logs, this document outlines the procedures and expectations for logging drill core at the CSL. This document describes the processes for storing, photographing, and logging core, and includes a variety of resources, reference materials, and appendixes designed to standardize and aid the logging process. Following the procedures outlined in this document will produce consistent, detailed logs that facilitate dependable observations and serve as an easy reference for researchers and other interested parties.

Modeling future groundwater depletion to evaluate sustainability goals set under the Sustainable Groundwater Management Act in the critically overdrafted basins of the Central Valley, California, USA (2020–2070)

Wed, 20 May 2026 14:13:52

In 2014, California's Sustainable Groundwater Management Act (SGMA) mandated local agencies to devise and implement groundwater sustainability plans to address critically overdrafted conditions throughout the state's aquifers. However, the feasibility of these agencies' sustainability goals has not previously been assessed through a regional-scale, integrative lens. Here, we develop and analyze a novel, basin-wide database of 936 sustainability indicator wells located within Central Valley subbasins designated as critically overdrafted, most of which lie in the San Joaquin Valley. Our database shows 2040 groundwater elevation goals vary widely from 60 m above to 80 m below 2020 levels, with variability within and between adjacent subbasins. To evaluate the feasibility of achieving these goals, we coupled the database with a regional hydrologic model (Central Valley Hydrologic Model version 2) and simulated multiple future pumping scenarios. Results show that under increased groundwater demand, 60%–70% of indicator wells may fail to meet their 2040 goals. Even a 50% reduction from 2020 demand levels leaves nearly 40% of wells failing to meet their sustainability thresholds by 2040. Baseline models show that by 2070, up to 70% of wells could fail to meet their goals due to large-scale, spatially connected regions of groundwater depletion. This integrated framework, linking the first region-wide compilation of SGMA indicator wells with a regional groundwater model, demonstrates that many local sustainability goals may be unattainable with substantial (up to 50%) reductions in pumping. Additional management interventions, such as expanded recharge or coordinated demand reductions, may help achieve sustainability goals.

Assessment of groundwater quantity and quality contributions to Lake Huron

Kaemming, Bridget; Ford, Chanse; Martin, Sherry — Fri, 24 Apr 2026 18:36:33

Lake Huron, one of the five Great Lakes, borders the United States and Canada, with Michigan as the only U.S. State on its shoreline. Like other freshwater lakes, it faces water-quality challenges from nutrients and chemicals applied across its drainage basin. Although past studies focused on surface-water sources, groundwater contributions remain less understood. To address this gap, the U.S. Geological Survey, as part of the Cooperative Science and Monitoring Initiative, classified drainage basins to Lake Huron into eight hydrogeologic zones based on bedrock rock type and glacial sediment transmissivity. Utilizing existing data and empirical field data, we quantified groundwater discharge and identified areas of concern for loading of chloride and nitrate to Lake Huron. Groundwater contributions, including indirect and shoreline discharge, ranged from 5.8 to 11.5 inches annually, totaling 1.9 cubic miles and 0.09 cubic mile, respectively. Hydrogeologic zones with higher glacial sediment transmissivity yielded greater indirect groundwater discharge. Chloride levels above the U.S. Environmental Protection Agency’s 250-mg/L recommendation were mainly in the Saginaw lowlands, whereas nitrate above the 10-mg/L standard was rare—found in only 11 wells. Together, the analysis of where groundwater discharge is occurring in the Lake Huron Basin and the identification of areas with potential groundwater-quality concerns can help prioritize areas that are critical to protecting the long-term health of Lake Huron.

A novel drive-point multilevel system to investigate PFAS and other contaminants of global concern in the hyporheic zone of a wastewater effluent dominated stream

Meyer, J.; Mianecki, A.; Occhi, E.; Kolpin, Dana W.; LeFevre, G. — Wed, 29 Apr 2026 14:14:57

Contaminants found in treated wastewater discharged to streams, including pharmaceuticals and per- and polyfluoroalkyl substances (PFAS), are of global concern due to their deleterious effects on aquatic ecosystems and potential impacts to human health. Hyporheic zones have strong potential for contaminant attenuation. Assessing this potential requires collection of physical and biogeochemical data within the hyporheic zone. This study tested the applicability of a novel drive-point multilevel system (DP-MLS) for quantifying head profiles and characterizing contaminant concentrations in the hyporheic zone of a temperate region effluent dominated stream (EDS). DP-MLS, each with 4 ports, were installed in the stream bed at two sites, DS-1 and DS-2, 0.2 and 4.7 km downstream of the effluent outfall, respectively. Head profiles were measured and groundwater collected for analysis of pharmaceuticals and PFAS temporally over two years. The DP-MLS withstood rapid changes in stage, ice formation, and floating debris. Vertical hydraulic gradients (VHG) were generally upward but varied in magnitude indicating heterogeneity in hydraulic conductivity and variability in flow conditions. Upward VHG were also about 2X larger at DS-1 than at DS-2. Contaminant concentration profiles consistently showed penetration of pharmaceuticals and PFAS to 1 m below the bed at DS-2 while there was less penetration, lower groundwater concentrations, and more temporal variability in concentrations at DS-1. Integration of the physical and chemical data suggests weaker upwelling conditions at DS-2 are more easily reversed during periods of high stream stage, which could facilitate migration of wastewater contaminants into the bed. However, further studies incorporating other transport processes and reach scale dynamics are required to fully characterize these exchanges. Overall, this study demonstrates the efficacy of these novel DP-MLSs for characterization of the hyporheic zone and provides new insights into the occurrence, composition, and persistence of wastewater derived contaminants in the hyporheic zone of a well-studied EDS.

The role of groundwater in contributing to surface water salinization in the Upper Colorado River Basin

Tue, 21 Apr 2026 15:13:37

Freshwater salinization impacts the availability of water for human use and ecosystem needs worldwide. It has been estimated that total dissolved solids (TDS) in the Colorado River Basin cause $350 million/year in damages and substantial resources are devoted to reducing TDS loading to streams. This study describes the development and application of coupled watershed models that enable TDS source tracking through the subsurface and across the landscape at a seasonal timestep for 35 years in the Upper Colorado River Basin. Results indicate that, on average, 75% of TDS loading to streams originates as baseflow, and 50% of loading is lagged in delivery by longer than one season. Snowmelt was identified as a dominant process controlling the transport of lagged TDS to streams. This approach informs when and where TDS mitigation efforts may be effective in a watershed that serves as a critical water supply for the southwestern United States.

Hydrogeology, groundwater salinity distributions, and assessment of the effect of oil-production activities on groundwater in the Midway Valley area, western Kern County, San Joaquin Valley, California

Fri, 24 Apr 2026 14:10:27

This study seeks to determine the effects of oil field produced water disposal operations and well mechanical integrity issues on groundwater quality in oil fields in the southwest San Joaquin Valley, California. Whereas previous studies used groundwater wells to study shallow aquifers outside the oil fields, this study demonstrates that future approaches may use oil well geophysical logs to map groundwater head gradients, create salinity profiles and document changes in salinity over time in oil field areas with sparse groundwater well data and at depths greater than 330 m. We also incorporate an analysis of well histories to determine potential effects of compromised wellbore seals on changes in aquifer quality that cannot be explained by water disposal practices. Water quality in the aquifers is naturally brackish across most of the area, with better quality groundwater occurring in the eastern part. Geophysical logs are used to determine salinity variations within aquifers including the depth at which TDS exceeds 10,000 mg/L. This depth ranges from 366 m in the northwest to approximately 1,500 m in the southeast. Oil well porosity logs are used to determine water table elevations. These logs indicate the water table slopes south-southeast, showing the predominant groundwater flow direction is from oil field disposal areas toward better quality groundwater east of the oil fields. Geophysical logs show formation resistivity near some disposal facilities has decreased over time, indicating the salinity of the aquifer has increased due to disposal of saline produced water in injection wells and ponds. Oil well history analysis suggests that increased salinity over time in water-saturated sand intervals >1.5 km from disposal facilities may be caused by mechanical failures and/or incomplete borehole seals in poorly constructed or abandoned wellbores prevalent throughout the study area—particularly wells drilled prior to 1930.

Water volumes, heat flow, and solute discharge from Old Faithful Geyser eruptions, Yellowstone National Park, USA

Tue, 21 Apr 2026 15:01:47

The iconic Old Faithful Geyser in Yellowstone National Park, USA, has attracted a significant amount of research because of the relative regularity and impressive size of its eruptions. Numerous studies have included observations, measurements, and analyses that informed models of geyser eruptions. However, fundamental quantities, including the associated mass and heat discharged, remain poorly constrained. In April 2025 we measured the volume of water from 45 Old Faithful Geyser eruptions using a portable flume in an outflow channel and specific conductance measurements in the Firehole River. We used high-speed video to perform velocimetry, measured changes in water chemistry to calculate the volume of water evaporated along the outflow channels, and used thermodynamic calculations to estimate the volume of water erupted as steam and to quantify the geyser's heat output. The calculated average volume of water discharged by Old Faithful Geyser in each eruption is 27.9 ± 9.4 m³, with no relation between eruption volume and the length of the preceding eruption interval. Video analysis of the eruption's liquid-dominated phase yields similar volumes of 21–30 m³. The calculated heat flow from the geyser is 2.2–2.4 MW and the average annual discharge of chloride, fluoride, and arsenic are 63 tons, 3.9 tons, and 241 kg, respectively. Average annual silica deposition rate on the geyser cone and along the outflow channels is 7 tons. This study provides a methodology for future studies at geysers worldwide and a baseline for monitoring future activity changes at Old Faithful.

Computation of regional groundwater budgets for the Virginia Coastal Plain aquifer system

Pope, Jason; Gordon, Alison; Frederiks, Ryan — Mon, 20 Apr 2026 17:44:26

Computation of detailed groundwater flow budgets for subdivisions of the Virginia Coastal Plain aquifer system has enabled quantification and more thorough understanding of groundwater flow within this important water resource. A zone budget analysis based on previously published groundwater models of the Virginia Coastal Plain and Virginia Eastern Shore indicates that groundwater conditions vary substantially throughout the Coastal Plain aquifer system because of local variations in hydrogeology and historical and ongoing variations in groundwater use and management. Decades of substantial groundwater withdrawal from the Coastal Plain aquifer system have altered groundwater flow from predevelopment conditions. Rates of sustainable withdrawal are limited because the downward groundwater flow rate into confined aquifers is a relatively small part of the total groundwater budget for the aquifer system compared to the rate of recharge at the land surface.

Analyses of groundwater budgets from the Virginia Coastal Plain model indicate that groundwater flow is generally outward from the surficial aquifer to rivers and coastal waterbodies and downward through a series of underlying aquifers and confining units to the Potomac aquifer, which is the deepest aquifer and the source of most groundwater withdrawals. Downward flow into the Potomac aquifer is estimated to be only 7 percent of total net precipitation-derived net recharge at the land surface but makes up about 66 percent of inflow to the aquifer in Virginia, with much of the remaining inflow occurring laterally from outside of defined groundwater budget regions in Virginia. For several decades prior to 2010, high rates of withdrawal from the Potomac aquifer resulted in substantial decline in groundwater storage in the aquifer and in most overlying aquifers and confining units. From 2010 to 2023, rates of withdrawal substantially lower than the historical maximum resulted in small net increases in groundwater storage in the confined aquifer system for most regions of the Virginia Coastal Plain. Nevertheless, for the same period, groundwater storage for the entire model domain continues to incrementally decline, indicating that storage recovery in Virginia is offset by a continued decrease in storage in areas beneath the Chesapeake Bay or adjacent areas of Maryland and North Carolina. Withdrawals from the Potomac aquifer have induced substantial downward flow which is a large part of groundwater budgets for confined aquifers such as the Potomac. For the most recent simulated conditions (2023) downward groundwater flow continues, but because vertical flow rates are a function of the difference between water pressure in the upper surficial systems and lower confined units, rates of downward flow are lower than those in earlier decades as the confined water levels partially recover from larger groundwater withdrawals in the past. Geographically, groundwater flow is generally inward from perimeter regions of the Virginia Coastal Plain toward central regions with the largest withdrawal rates. Groundwater inflow from coastal regions could be contributing to saltwater intrusion, even though that was not measured in this study.

Analyses of groundwater budgets from the Virginia Eastern Shore peninsula, a geographic region of the Virginia Coastal Plain, indicate that groundwater flow for that isolated aquifer system is generally outward from the surficial aquifer to coastal water bodies and downward into the confined Yorktown-Eastover aquifer system, which is the source of most withdrawals. Downward groundwater flow into the confined Yorktown-Eastover aquifer system is estimated to be less than 2 percent of total recharge and less than 9 percent of net recharge at the water table but makes up more than 93 percent of all inflow to the confined aquifer system. Decades of substantial but relatively consistent groundwater withdrawals have induced greater downward flow rates into the confined aquifer system but also have resulted in loss of groundwater from storage. For the most recent simulated period (2023), estimated storage loss accounts for slightly under 7 percent of withdrawals from the confined aquifer system. The reported withdrawal rate for this period from the confined Yorktown-Eastover system is near the highest reported rate for the Virginia Eastern Shore, which means that the storage depletion is expected to continue, even though groundwater levels appear to be relatively stable. Estimated groundwater flow rates upward from the confining unit underlying the Yorktown-Eastover system and low rates of inflow from coastal water bodies underscore ongoing concerns about up-coning and lateral intrusion of salty groundwater.

Historical ice jams and associated environmental conditions on Osoyoos Lake

Sutfin, Nicholas; Breen, Stephen — Mon, 20 Apr 2026 17:42:39

Ice jams occur regularly at the southern outlet of Osoyoos Lake, which spans the border between the State of Washington and British Columbia, Canada. In recent winters, ice jams caused (1) decreases in downstream discharge that may adversely affect salmon spawning habitat and (2) short-duration lake-level rise that can interfere with lake level management agreements. In response, water managers sought to understand the environmental conditions associated with the historical ice-jam occurrences on Osoyoos Lake. Researchers compiled datasets of discharge, lake level, and air temperature from four meteorological and three hydrologic stations near Oroville, Washington, to determine “ice-jam” or “non-ice-jam” days from 1942 to 2024.

After confirming known ice jams since 1994 using Landsat 8–9 and Sentinel–2 satellite imagery along with discharge, lake level, and air temperature data, researchers designated ice-jam days. They conducted statistical analyses to examine environmental conditions associated with ice-jam occurrences on Osoyoos Lake. Statistical tests indicated significant differences in wind speed, wind direction, and air temperature between ice-jam and non-ice-jam days. A linear discriminant-analysis model correctly predicted 12 of 13 historical ice-jam days since 1994 and determined that ice jams are more likely under westerly and northwesterly winds near or above 10 kilometers per hour (km/h) and minimum temperatures near or below –9.4 degrees Celsius (°C). An analysis of historical discharge suggests that ice jams have occurred since at least the 1940s, but 13 ice jam days occurred in the past decade (2014–2024), exceeding any previous decade. The daily minimum air temperature in the Osoyoos Lake region has increased at a rate of 0.021 °C per year since the 1940s, but ice jams usually occur in winters with colder average temperatures.

Comparative assessment of STIC sensors, streamflow and rain gauges for quantifying river connectivity in intermittent systems

Cooper, Cienna; Rogosch, Jane; Smith, Nathan; Robertson, Clinton; Wilson, Wade — Mon, 4 May 2026 16:56:07

In intermittent stream systems, including those occurring in Texas, USA, the severity of low-flow conditions, duration of seasonal disconnection, and frequency of no-flow events have been amplified by drought. Documentation of these no-flow events is necessary to evaluate ecosystem health. However, many intermittent reaches remain un-gauged given that perennial river sec-tions are often prioritized for gauge placement. Our objectives were to 1) document stream flow using Stream Temperature, Intermittency, and Conductivity (STIC) loggers to determine the frequency and duration of no-flow events in intermittent tributaries of the Colorado River, Texas and 2) compare logger data to publicly available data from streamflow discharge and precipitation gauge networks to understand differences among these data types for drying event characterization. We use these comparisons to summarize benefits and limitations of the application of in-stream data loggers. STIC loggers were deployed at 19 sites, one in each pool and riffle habitat of a stream reach. STIC loggers recorded a measurement of relative conductance every six hours from June 2022 to March 2024, which was used to determine the presence or absence of flow connectivity in a reach. No-flow duration among intermittent reaches varied between 37 and 270 days across tributaries during an ongoing drought in the study area. Overall, logger data was more precise than discharge data for characterizing no-flow events or precipitation data when documenting presence of water in the stream channel due to runoff. Lack of discharge gauges in intermittent tributaries left large sections of stream reaches undocumented and resulted in mischaracterization of flow patterns. Drought severity across the tributaries did not follow longitudinal patterns that would be expected by the climatic precipitation gradient of the study area. More research is needed to determine if factors such as population size affect severity. Likewise, precipitation data did not correlate well with logger water presence data, lacking consideration for groundwater recharge, soil hydrophobicity, and surface compaction. This study shows that to monitor no-flow events, detailed spatial datasets are necessary and that STIC loggers are useful tools that provide data to fill spatial information gaps and facilitate more accurate flow characterization and water presence data in intermittent systems.

Late Miocene Colorado River arrival in the Bidahochi basin supports spillover origin of Grand Canyon

Fri, 24 Apr 2026 14:51:49

The timing and mechanism of the integration of the Colorado River and incision of the Grand Canyon remain among geology’s enduring controversies. A key question is the configuration of the upper Colorado River watershed between 11 and 6 million years ago. In this study, we present new evidence from zircon uranium-lead geochronology for the arrival of distinctive Colorado–Green River sediment in the Bidahochi basin by 6.6 million years ago derived from the Browns Park Formation. This is coeval with an order-of-magnitude increase in depositional rate, an increase in carbonate strontium isotope (⁸⁷Sr/⁸⁶Sr) ratios, the appearance of large fish species characteristic of fast-flowing waters, and other sedimentological changes. This evidence is consistent with the Colorado River supplying water and sediment to the Bidahochi basin before spillover integration of the river through the Grand Canyon.

Logical data model for hydrographic data based on HY_Features concepts

Mon, 18 May 2026 14:33:53

This report describes background and design of the “hydrofabric data model” which defines logic for implementation of data schemas and software that deals with hydrologic geospatial data. As a “logical” data model, the hydrofabric data model specifies details necessary to support compatibility of data and software that satisfy diverse needs without unnecessarily restricting implementation details. The logic presented in this report is based on concepts defined in WaterML2 Part 3 Surface Hydrology Features Concepts and is designed to serve the needs of a range of hydroscience use cases.

Development of international community standards applicable to hydrofabrics began, prompted by the World Meteorological Organization Commission for Hydrology, in 2012 [5] . More than 10 years later, this report documents one aspect of a long-term research and development activity that traces its roots back that far.

This report describes terminology, use cases, and background as context preceding presentation of the logical model and discussion of its design. Three appendices document related data models, an example encoding of the hydrofabric data model, and an artificial schematic and tabular data example. The sections of the report can be accessed in the Clause 5 section.

Analyses of meteorological and hydrological records support Tribal members’ accounts of changing climate on the Fort Apache Reservation, east–central Arizona

Mason, Jon — Mon, 20 Apr 2026 17:40:45

The Fort Apache Reservation in east–central Arizona, home to the White Mountain Apache Tribe of the Fort Apache Reservation, Arizona, contains several climate zones because of the large variation in surface elevation within the reservation. This study was carried out in cooperation with the White Mountain Apache Tribe of the Fort Apache Reservation, Arizona, to raise awareness of how the changing climate affects the Fort Apache Reservation. This report documents the evaluation of existing multidecadal meteorological and hydrological datasets for the Fort Apache Reservation, used to evaluate the effects of a changing climate on the reservation. In this evaluation, near-surface air temperature, snow depth, snow water equivalent, precipitation, and streamflow datasets were analyzed for monotonic trends indicative of changing climatic conditions during specified periods of time. The results of these trend analyses were then compared with the Tribal community's memories of the changing climate.

Trend analysis of near-surface air temperatures from a U.S. Historical Climatological Network station on the Fort Apache Reservation at Whiteriver, Arizona, indicated that mean annual air temperatures have increased by an average of 2.48 degrees Fahrenheit from 1980 to 2023. Records from the same station also indicated that average monthly maximum temperatures recorded for March increased by 5.39 degrees Fahrenheit for the same time period.

Annual precipitation at the five precipitation stations used in this study decreased greatly from the 1980s to 2023. The largest total decrease was 10.07 inches, or 34.7 percent. However, only one of the two precipitation stations with longer term data available prior to 1980 had a significant negative trend when data from the entire period of record, from 1901 to 2023, were analyzed.

Trend analyses show a decrease in the annual maximum snow water equivalent and an earlier disappearance of the snowpack at two Natural Resources Conservation Service snow telemetry stations in the mountainous region just east of the Fort Apache Reservation from 1981 to 2023. Based on the trend analyses, the average annual maximum snow water equivalent has decreased by more than 40 percent at both stations, and the average date when the snowpack was fully melted at the stations in the spring has moved earlier in time from late April to early April or late March. However, a statistically significant trend was not determined for the early April snow water equivalent measured at a nearby Natural Resources Conservation Service snow course across its period of record, indicating that the history of mountain snowpack in this area is not fully understood. Analysis of snowfall data from a National Oceanic and Atmospheric Administration Cooperative Observer Program network station on the Fort Apache Reservation at McNary 2N, AZ (station 025412) indicated that, on average, the measured total annual snowfall at the station decreased 42.4 percent from 1935 to 2023.

Streamflow data from six U.S. Geological Survey streamgages on the Fort Apache Reservation were analyzed for trends. For most streamflow gages, statistically significant trends were not determined for tested parameters when the entire streamflow period of record was used for stations with records going back to at least the 1960s. However, when the data from 1980 to 2023 was tested, most of the streamflow parameters had statistically significant negative trends. All six streamgages showed a decrease in average annual runoff of at least 50 percent from 1980 to 2023; one streamgage showed an 81.8 percent decrease.

A similar statistical finding was observed in the analysis of the annual spring snowmelt peak from one of the six streamgages used in the study and located in an area receiving measurable amounts of snowmelt runoff. When data from the entire period of record (1958–2023) was used, no trend in streamflow was determined; however, a significant negative trend was determined from 1980 to 2023, indicating a decrease in average annual springtime runoff of 62.6 percent. Statistical analysis on the timing of the annual spring snowmelt peak at the same streamgage indicated the snowmelt peak is happening on average about 12 days earlier now (2023) than it did in the past. The trend results for the timing of the annual spring snowmelt peak were the same and statistically significant for both periods tested (1958–2023 and 1980–2023). Two of the streamflow records from the Fort Apache Reservation were compared to the Palmer Hydrological Drought Index computed for Arizona Climate Division 4 (East Central) by the National Centers for Environmental Information. The comparison showed that the streamflow records generally tracked the Palmer Hydrological Drought Index.

In interviews, Tribal community members living on the Fort Apache Reservation described the changes in climate that they observed during their lifetimes. Common themes reported were that air temperatures have become warmer, and the weather is less predictable with changes in seasonal patterns. Drier conditions, lower snowfall, shorter winters, and lower river levels were also reported. These community member observations align with the results of this study.

The global proliferation of aquatic, benthic Microcoleus: Taxonomy, distribution, toxin production, ecology, and future directions

Wed, 11 Feb 2026 15:20:31

There have been sporadic reports of aquatic, benthic Microcoleus proliferations in freshwater rivers, lakes, and reservoirs for four decades, with reports increasing in frequency over the last twenty years, suggesting a possible rise in their global distribution, frequency, and intensity. Microcoleus can produce anatoxins which are neurotoxic, and ingestion of toxic mats has caused hundreds of dog fatalities and raised serious human and ecological health concerns. This review synthesizes and evaluates current knowledge on Microcoleus distribution, taxonomy, toxin production, toxicity, ecology, environmental drivers, and biotic interactions. Toxin-producing Microcoleus have been reported in at least 18 countries, though many regions have not conducted toxin testing, suggesting a broader but under-reported distribution. Proliferations occur across diverse habitats, including cobble-bedded streams, large sandy rivers, reservoirs, and lakes. Microcoleus proliferations also occur on macrophytes, both in lakes and rivers. Genomic analyses currently classify anatoxin-producing Microcoleus into distinct species, with all known anatoxin-producers isolated from freshwater ecosystems. Anatoxin concentrations vary widely over space and time, within and among waterbodies. While studies on environmental drivers remain limited, research in cobble-bedded rivers suggests that moderate enrichment of dissolved inorganic nitrogen and low dissolved reactive phosphorus concentrations in the water column promote proliferation. Metagenomic approaches have revealed unique nutrient acquisition and storage strategies used by Microcoleus. Key knowledge gaps remain around the environmental and ecological triggers of proliferation, toxin production, genomic diversity and microbial interactions. Addressing these gaps through coordinated, global studies using robust datasets and consistent methods is critical to improve prediction, monitoring, and mitigation of this increasingly widespread public and ecological health threat.

Mount Rainier volcanic hazard information

Weiss-Racine, Holly; Bard, Joseph A.; Ball, Jessica; Mastin, Carolyn — Mon, 20 Apr 2026 17:37:33

Introduction

Eruptions at Mount Rainier produce lava flows, plumes of airborne volcanic ash, and avalanches of hot rock, ash, and gas—pyroclastic flows—that rush down the steep, ice-covered slopes of the volcano. Hot rock and ash ejected during an eruption can melt large quantities of snow and ice, forming huge, fast moving mudflows called lahars that travel 30+ miles, all the way to Puget Sound. Very large lahars can also form when weak and water-saturated rock high on the volcano collapses with or without volcanic activity. Learn more inside!

Evaluation of benthic habitat change within the national historic sites of Hawaiʻi’s Kona Coast

Mon, 20 Apr 2026 17:39:04

Executive Summary

Coral bleaching events have become increasingly common across the Hawaiian Archipelago since 1996 because of more frequent and intense marine heatwaves. The most significant bleaching event to date occurred from 2014 to 2015, which resulted in catastrophic state-wide coral loss. Bleaching events with less severe effects also occurred in 1996 and 2019. To understand the long-term effects of repeated bleaching events, along with other anthropogenic factors such as water quality, storms, sewage runoff, and coastal development, on coral reefs on the Kona Coast of the Island of Hawaiʻi, the U.S. Geological Survey, in collaboration with the National Park Service, collected underwater imagery in the early 2000s (baseline survey) and again in 2022 (resurvey). These images were captured within and adjacent to the National Historic Parks (NHP) and National Historic Sites (NHS) of Kaloko-Honokōhau NHP (KAHO), Puʻuhonua o Hōnaunau NHP (PUHO), and Puʻukohola Heiau NHS (PUHE). Imagery was classified for live coral cover and dominant type (four coral types, rubble, macroalgae, and two bottom substrate types). Change of percent live coral cover was determined for all sites. Change of coral and non-coral dominant types were calculated by aggregating classifications for each park into coral and non-coral. Net coral cover decreased between the baseline and resurvey period across all three parks, though PUHE exhibited the greatest loss of live coral cover. Across all three parks, the occurrence of lower coral cover classes (0–20 percent) increased and higher coral cover classes (greater than 50 percent) decreased. Furthermore, the total occurrence of non-coral dominant type classifications (rubble, macroalgae, sand, and volcanic pavement) increased by approximately 25 percent across all three parks, with PUHE experiencing a nearly 90-percent increase in the occurrence of non-coral types. There was little to no effect of water depth on change of live coral cover, indicating that marine heatwave driven bleaching events and additional anthropogenic influences affected the entire reef across all water depths from the lower fore reef to the reef flat.

Because coral loss was more severe at PUHE and PUHO than KAHO, creating a monitoring framework that utilizes periodic underwater camera surveys and fixed diver transects by the National Park Service would contextualize the periodic spatial surveys to the fixed transects that have greater temporal resolution. Similarly, increased frequency of spatial surveys would allow for the National Park Service to continue monitoring changes to critical nearshore habitats and marine resources relevant to National Park jurisdiction.

Assessment of natural gas pipeline construction on stream temperature and turbidity in southwestern Virginia, 2017–25

Foster, Brendan; Maas, Carly; Flota, Alejandra — Mon, 27 Apr 2026 18:42:46

Despite the extensive natural gas pipeline network in the United States that intersects streams and other sensitive habitats, few case studies use a comparative upstream-to-downstream approach to evaluate potential short- and long-term effects of pipeline stream crossings from pre-construction through post-restoration. In 2017, the U.S. Geological Survey, in cooperation with the Virginia Department of Environmental Quality, deployed real-time continuous stream monitoring stations upstream and downstream from six proposed Mountain Valley Pipeline stream crossings in southwestern Virginia. Water temperature and turbidity data collected at the upstream and downstream sites were compared across three periods—before stream crossing construction, during stream crossing construction, and after stream crossing construction—to determine potential influences from the pipeline stream crossing. Additionally, the monitoring network was used to notify regulators of potentially anomalous conditions throughout the entire monitoring period.

The results of this study indicate that pipeline stream crossing did not affect long-term or short-term upstream-to-downstream water temperature conditions or long-term upstream-to-downstream turbidity conditions in any of the six monitored streams. Some short-term anomalously elevated turbidity conditions were observed and attributable to pipeline stream crossing; however, the magnitudes and durations were not sufficient to alter the long-term turbidity regimes of the streams in which they were observed. The application of the monitoring network as a real-time alert system successfully alerted regulators to potentially anomalous conditions.

Proceedings of the Floodplain Vegetation Monitoring Workshop for the Long Term Resource Monitoring Element of the Upper Mississippi River Restoration Program, January 7–8, 2025, Moline, Illinois

Wed, 15 Apr 2026 14:24:34

Preface

In anticipation for increased funding made possible by the Water Resources Development Act of 2020, the Upper Mississippi River Restoration (UMRR) Program identified a need to conduct river-wide assessments of floodplain vegetation. In January 2025, we assembled a group of subject matter experts to perform the following tasks:

Review Upper Mississippi River Restoration’s current floodplain vegetation research portfolio,
Identify important features and goals for long-term floodplain vegetation monitoring,
Evaluate the suitability of existing datasets for system-wide vegetation assessments, and
Discuss emerging opportunities to learn about floodplain vegetation dynamics from local-scale restoration and management projects.

This document is a summarization of what occurred at the meeting and provides suggested next steps toward developing the capacity to conduct routine long-term monitoring and assessment of floodplain vegetation as part of the Upper Mississippi River Restoration Program.

Opportunities and challenges in using Solid Phase Adsorption Toxin Tracking (SPATT) samplers for monitoring cyanotoxins in freshwater and estuarine environments

Tue, 28 Apr 2026 17:26:16

Cyanobacterial toxins (cyanotoxins) represent a substantial threat to drinking water supplies and safe recreational uses of freshwater resources in watersheds worldwide. Monitoring cyanotoxins can be difficult because toxin events are variable in both space and time, are not always persistent, can be moved easily by wind and currents, and may be degraded biotically or abiotically. Thus, monitoring programs that collect discrete samples on a monthly or even bimonthly interval can miss key events and underestimate cyanotoxin risk or if they capture a high-concentration event, can give a false impression that cyanotoxins are a widespread health hazard. The use of Solid Phase Adsorption Toxin Tracking (SPATT) samplers helps address this issue by providing a time-weighted average estimate of dissolved cyanotoxin occurrence and relative concentrations. SPATT samplers have been used as a complement to traditional monitoring programs and can help elucidate cyanotoxin dynamics. SPATT samplers have been used by six U.S. Geological Survey (USGS) Water Science Centers (New York, California, Oregon, Upper Midwest, New Jersey, and Lower Mississippi-Gulf) to monitor various cyanotoxins in waterbodies such as streams, rivers, lakes, waterfalls, estuaries, and drinking-water intakes. Despite their use across the USGS, there is little guidance available to ensure consistent approaches and data quality across the Bureau. This report summarizes best practices for SPATT deployment and analysis, synthesizes data and describes lessons learned from USGS studies, identifies priority knowledge gaps, and offers considerations for future targeted experiments to help improve data collection and interpretation.

The Sedimentary Geochemistry and Paleoenvironments Project Phase 2 data release: An open data resource for the study of Earth's environmental history

Wed, 22 Apr 2026 15:01:35

Geochemical data from sedimentary rocks are the primary source of information regarding Earth's surface evolution through time, including its air and water envelopes and interactions with life and deep Earth processes. The Sedimentary Geochemistry and Paleoenvironments Project (SGP) is a scientific consortium centered around open data and community-driven development of cyberinfrastructure tools and resources for sedimentary geochemistry and Earth history. Here we describe the SGP Phase 2 data release, which focused on incorporating Paleoproterozoic and Mesoproterozoic (2500–1000 million years ago) data and better accommodating carbonate data. This data release was built through the involvement of >200 researchers worldwide in academia, government, and industry, and provides the largest available public data resource for our user community in the academic fields of geochemistry, sedimentology, tectonics, paleontology, Earth history, and paleoclimate, as well as the petroleum and minerals industries. The dataset now encompasses 126,006 samples and 4,132,371 geochemical analyses. In addition to direct entry by SGP Team Members, we have ingested and incorporated datasets from the Geoscience Australia OZCHEM database, the Alberta Geological Survey, and the Deep-Time Marine Sedimentary Element Database (DM-SED) compilation. This paper details sampling in the Phase 2 dataset with respect to age, geography, lithology, and other geological characteristics, documents access via our search website and API, discusses possible issues and/or biases in the dataset that could impact analyses, describes plans for governance and stewardship of data from Indigenous lands, and serves as the citable reference paper for the data release.

Hydrogeology of the Tully Valley and characterization of mudboil activity, Onondaga County, New York

Kappel, William; Sherwood, Donald; Johnston, William — Tue, 9 Jun 2026 20:15:31

Mudboil activity in the Tully Valley, in central New York, is causing turbidity in nearby Onondaga Creek, where it has caused a bridge to collapse; it also has threatened or damaged other structures and has caused extensive land subsidence. Mudboil activity was intermittent from its first reported appearance in the 1890's until the 1970's, when the rates of mudboil discharge and land subsidence began to increase. Historically, the water discharged from mudboils was reported as fresh, but chemical analyses in the late 1970's indicated an increase in specific conductance and chloride concentration.

Mudboil discharge is driven by artesian pressure in unconsolidated sediments that are confined by a 60-foot layer of silt and red clay. This process, once begun, has been self-propagating. Artesian pressures are about 20 feet above land surface over most of the valley floor but exceed 30 feet above land surface along Onondaga Creek where Rattlesnake Gulf and Rainbow Creek enter the Tully Valley. The source of artesian pressure is recharge from the Tully (Valley Heads) Moraine at the south end of the valley, and the alluvial fans of Rattlesnake Gulf and Rainbow Creek. The mudboils are found within a 300-foot-wide by 1,500-foot-long corridor along Onondaga Creek just upstream from the two alluvial fans, and in a 5-acre subsided area just west of that corridor.

Remediation efforts have entailed (1) diversion of flow from the tributary that feeds the subsided area, (2) installation of depressurizing wells at several locations, and (3) construction of a dam and settling impoundment to detain mudboil sediment that would normally discharge to Onondaga Creek. These efforts have been partly successful, but further work is needed to slow the mudboil activity, which is expected to persist in both areas. Mudboil activity is normally greatest during the early spring and late fall, when artesian pressures increase in response to seasonal ground-water recharge.

Suspended-sediment concentrations at the out-flow of the subsidence area ranged from 31,210 mg/L (milligrams per liter) in October 1991 to 17 mg/L after remediation efforts in the summer of 1993. Yearly average suspended-sediment loads to Onondaga Creek from the subsidence area for water years 1992, 1993, 1994, and 1995 were 29.8, 9.75, 1.41, and 1.80 tons per day, respectively. Sediment discharged from the mudboils initially was 30 to 60 percent clay and 80 to 100 percent silt-sized or smaller sediment, and the sand fraction never exceeded 20 percent. After the remediation projects, 50 to 80 percent was clay, and nearly all sediment was silt size or smaller.

Analyses of water from upstream and downstream of the subsidence area, as well as from mudboil vents within that area, indicate that the source of water for some mudboils is a confined freshwater aquifer, whereas for others it is an underlying, brackish-water aquifer. Water from the freshwater aquifer has specific conductance values ranging from about 400 (μS/cm (microsiemens per centimeter at 25° Celsius) to almost 900 (μS/cm, dissolved chloride concentrations range from 37 to 430 mg/L, and dissolved-solids concentrations range from 215 to 463 mg/L. Specific conductance of water from the brackish-water aquifer ranges from 17,000 to 28,000 (μS/cm, chloride concentrations range from 2,000 to 7,100 mg/L, and dissolved-solids concentrations range from 4,200 to 12,800 mg/L.

The largest landslide in New York State in the last 75 years occurred at the foot of Bare Mountain, 1 mile downstream from the mudboil area, in April 1993 and was the fourth in a series of slides that have occurred at the base of this hill. Slope instability was reported as early as May 1990. After the slide, intermittent mudboil-like activity was observed at several springs within the backscarp of the slide; water from these springs ranged from fresh to brackish. The chemical similarity between water from some springs in the backscarp area and water in the lower (brackish) aquifer beneath the mudboil area may indicate a hydraulic connection between this aquifer and the surficial deposits.

Hydrologic changes in the valley during the last 100 years have been attributed to salt-solution mining in the upstream (southern) end of the valley. The removal of nearly 150 feet of salt from four evaporite beds in the Syracuse Shale of the Salina Group has caused the collapse of bedrock and unconsolidated deposits in and near the brine field, 3 miles south of the mudboil area. These collapses have created a hydraulic connection among bedding plane aquifers in the bedrock and increased the hydraulic connection with unconsolidated aquifers. The ground-water flow system after brine field closure in 1988 may have reached a new semiequilibrium, but mudboil activity will likely continue because artesian pressures remain. Whether mudboils were present before salt solution-mining began is unknown.

Fluvial sediment data for Iowa—Suspended-sediment concentrations, loads and sizes; bed-material sizes; and reservoir siltation

Schuetz, Joel; Matthes, Wilbur — Mon, 8 Jun 2026 18:12:28

This report is a compilation of the fluvial sediment data collected and published by the U.S. Geological Survey and other Federal agencies for the State of Iowa. The compilation includes daily extremes, monthly summaries, particle-size analyses of suspended-sediment, particle-size analyses of bed materials at some daily suspended-sediment stations, suspended-sediment concentrations and loads for samples collected at periodic and miscellaneous sites, and reservoir sedimentation studies on streams.