Search Results

This paper reports on a project to compare predictions from a range of catchment models applied to a mesoscale river basin in central Germany and to assess various ensemble predictions of catchment streamflow. The models encompass a large range in inherent complexity and input requirements. In approximate order of decreasing...

A one-dimensional heat-transport model for conduit flow in karst aquifers is presented as an alternative to two or three-dimensional distributed-parameter models, which are data intensive and require knowledge of conduit locations. This model can be applied for cases where water temperature in a well or spring receives all or part...

Determining atmospheric deposition rates of mercury and other contaminants using lake sediment cores requires a quantitative understanding of sediment focusing. Here we present a novel approach that solves mass-balance equations for two cores algebraically to estimate contaminant contributions to sediment from direct atmospheric fallout and from watershed and in-lake focusing....

This paper describes a new divide and conquer approach that leverages big environmental data, utilizing all available categorical and time-series data without subjectivity, to empirically model hydrologic and water-quality behaviors across expansive regions. The approach decomposes large, intractable problems into smaller ones that are optimally solved; decomposes complex signals into...

Current-use pesticides associated with suspended sediments were measured in the San Joaquin River, California and its tributaries during two storm events in 2008. Nineteen pesticides were detected: eight herbicides, nine insecticides, one fungicide and one insecticide synergist. Concentrations for the herbicides (0.1 to 3000 ng/g; median of 6.1 ng/g) were...

The Des Moines River that drains a watershed of 16,175 km2 in portions of Iowa and Minnesota is impaired for nitrate-nitrogen (nitrate) due to concentrations that exceed regulatory limits for public water supplies. The Soil Water Assessment Tool (SWAT) model was used to model streamflow and nitrate loads and evaluate...

Three sediment cores were collected off the Mississippi River delta on the Louisiana Shelf at sites that are variably influenced by recurring, summer-time water-column hypoxia and fluvial loadings. The cores, with established chronology, were analyzed for their respective carbon, nitrogen, and sulfur elemental and isotopic composition to examine variable...

The purpose of this paper is to identify simple connections between observations of hydrological processes at the hillslope scale and observations of the response of watersheds following rainfall, with a view to building a parsimonious model of catchment processes. The focus is on the well-studied Panola Mountain Research Watershed (PMRW),...

With the goal of improving the understanding of the subsurface structure beneath the Harkins Slough recharge pond in Pajaro Valley, California, USA, we have undertaken a multimodal approach to develop a robust velocity model to yield an accurate seismic reflection section. Our shear-wave reflection section helps us identify and map...

Bear Lake sediments were predominantly aragonite for most of the Holocene, reflecting a hydrologically closed lake fed by groundwater and small streams. During the late Pleistocene, the Bear River flowed into Bear Lake and the lake waters spilled back into the Bear River drainage. At that time, sediment deposition was...

The release of endocrine-disrupting chemicals (EDCs) in wastewater treatment plant (WWTP) effluent poses a significant threat to the ecology of surface water receptors, due to impacts on the hormonal control, sexual development, reproductive success and community structure of the indigenous aquatic organisms and associated wildlife. Among the EDCs commonly observed...

The effects of sediment, ground-water, and surface-water processes on the timing, quantity, and mechanisms of N and P fluxes were investigated in the Wood River Wetland 57 years after agricultural practices ceased and seasonal and permanent wetland hydrologies were restored. Nutrient concentrations in standing water largely reflected ground water in...

New isotope laboratories can achieve the goal of reporting the same isotopic composition within analytical uncertainty for the same material analysed decades apart by (1) writing their own acceptance testing procedures and putting them into their mass spectrometric or laser-based isotope-ratio equipment procurement contract, (2) requiring...

The kinetics of iodide (I−) and molecular iodine (I2) oxidation by the manganese oxide mineral birnessite (δ-MnO2) was investigated over the pH range 4.5–6.25. I− oxidation to iodate (IO3-)">(IO3-) proceeded as a two-step reaction through...

Streamflow characteristics in the Yukon River Basin of Alaska and Canada have changed from 1944 to 2005, and some of the change can be attributed to the two most recent modes of the Pacific Decadal Oscillation (PDO). Seasonal, monthly, and annual stream discharge data from 21 stations in the Yukon...

Sedimentary basins in general, and deep saline aquifers in particular, are being investigated as possible repositories for large volumes of anthropogenic CO2 that must be sequestered to mitigate global warming and related climate changes. To investigate the potential for the long-term storage of CO2 in such aquifers, 1600 t of...

The haloalkaliphilic bacterium Alkalilimnicola ehrlichii is capable of anaerobic chemolithoautotrophic growth by coupling the oxidation of arsenite (As(III)) to the reduction of nitrate and carbon dioxide. Analysis of its complete genome indicates that it lacks a conventional arsenite oxidase (Aox), but instead possesses two operons that each encode a putative...

The naturally abundant nitrogen in soil and aquatic NOM samples from the International Humic Substances Society has been characterized by solid state CP/MAS 15N NMR. Soil samples include humic and fulvic acids from the Elliot soil, Minnesota Waskish peat and Florida Pahokee peat, as well as the Summit Hill soil...

The seasonal occurrence of organic contaminants, many of which are potential endocrine disruptors, entering the Potomac River, USA, watershed was investigated using a two-pronged approach during the fall of 2005 and spring of 2006. Passive samplers (semipermeable membrane device and polar organic chemical integrative sampler [POCIS]) were deployed in tandem...

[1] The quality and quantity of dissolved organic matter (DOM) exported by Arctic rivers is known to vary with hydrology and this exported material plays a fundamental role in the biogeochemical cycling of carbon at high latitudes. We highlight the potential of optical measurements to examine DOM...

The biogeochemistry at the interface between sediments in a seasonally ponded wetland (slough) and an alluvial aquifer contaminated with landfill leachate was investigated to evaluate factors that can effect natural attenuation of landfill leachate contaminants in areas of groundwater/surface-water interaction. The biogeochemistry at the wetland-alluvial aquifer interface differed greatly between...

Knowledge of key sources and biogeochemical processes that affect the transport of nitrate (NO3-) in streams can inform watershed management strategies for controlling downstream eutrophication. We applied dual isotope analysis of NO3- to determine the dominant sources and processes that affect NO3- concentrations in six stream/river watersheds of different land...

Investigations within the Silverton caldera, in southwestern Colorado, used a combination of traditional geological mapping, alteration-assemblage mapping, and aqueous geochemical sampling that showed a relationship between geological and hydrologic features that may be used to better understand the provenance and evolution of the water. Veins containing fluorite, huebnerite, and elevated...

Microbial mats are a visible and abundant life form inhabiting the extreme environments in Yellowstone National Park (YNP), WY, USA. Little is known of their role in food webs that exist in the Park's geothermal habitats. Eukaryotic green algae associated with a phototrophic green/purple Zygogonium microbial mat community that inhabits low-temperature regions...

Three-dimensional density-dependent flow and transport modeling of the Floridan aquifer system, USA shows that current chloride concentrations are not in equilibrium with current sea level and, second, that the geometric configuration of the aquifer has a significant effect on system responses. The modeling shows that hydraulic head equilibrates first, followed...