Temporal Changes in Nutrient Concentrations in the Lower Grand River and Selected Drainage Basins, Missouri and Iowa, During the Mississippi River Basin Healthy Watersheds Initiative (2010–23)
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- Document: Report (2.4 MB pdf) , HTML , XML
- Table: Tables 1.1 to 1.5 (xlsx)
- Dataset: USGS National Water Information System database - USGS water data for the Nation
- Data Release: USGS data release - Archive of the load estimation models used in the analyses of temporal changes in nutrient concentrations in the Lower Grand River and selected drainage basins, Missouri and Iowa (2010–23)
- Download citation as: RIS | Dublin Core
Abstract
This report describes a cooperative study by the U.S. Geological Survey and Missouri Department of Natural Resources that evaluated temporal changes in total nitrogen (TN) and total phosphorus (TP) concentrations in the Lower Grand River hydrologic unit. The study focused on trends since 2010, when the basin was designated as a priority drainage basin of the Mississippi River Basin Healthy Watersheds Initiative (MRBI). At three local drainage basins within the Lower Grand hydrological unit (MRBI sites), stream nutrient trends were evaluated using flow-adjusted (FA) TN and TP concentrations for water years 2011 through 2023. FATN concentration trends were not statistically significant for any MRBI site. One site (site 2) showed a statistically significant increasing trend in FATP concentration, indicating a possible increase in phosphorus sources in parts of the basin. Overall, streamflow variability appeared to be the dominant factor affecting nutrient concentrations at MRBI sites. At five regional drainage basins, including the Grand River and nearby rivers with data from 1994 through 2023 (long-term sites), annual flow-normalized (FN) TN and TP concentrations were evaluated for trends before (water years 2000–10) and during (water years 2010–23) the MRBI. For water years 2010 through 2023, annual FNTN and FNTP concentrations decreased in the Grand River, as well as in the Nodaway and Chariton Rivers, which were not targeted by the MRBI. The Grand River (site 9) reversed from increasing to decreasing FNTP concentrations after 2010, with a 26-percent reduction. Annual FNTN and FNTP concentrations also decreased at the Missouri River sites. While nutrient reductions in the Grand River may reflect the effects of implemented conservation practices, similar trends in nearby, nontargeted rivers and the absence of strong decreasing trends at MRBI sites suggest that broader regional factors, instead of or in addition to MRBI efforts, may have contributed to nutrient reductions in the Grand River.
Plain Language Summary
The U.S. Geological Survey, in cooperation with the Missouri Department of Natural Resources, estimated total nitrogen and total phosphorus concentrations at three local and five regional monitoring sites in Missouri. Temporal changes in total nitrogen and total phosphorus were quantified to evaluate whether instream nutrient concentrations have changed at local or regional scales. At the local scale sites, total phosphorus concentrations substantially increased at one site, which indicated a possible increase in phosphorus sources in the Lower Grand River hydrologic unit, while total nitrogen concentrations did not change substantially. At the regional site, annual total nitrogen and total phosphorus concentrations generally decreased. The regional decline in stream nutrients paired with the lack of nutrient reduction at the local sites indicated that nutrient reductions in the Grand River may have been driven by regional changes in nutrient export, instead of or in addition to conservation practices implemented as part of the Mississippi River Basin Healthy Watersheds Initiative.
Suggested Citation
Kamrath, B.J.W., Lauderback, C.N., and Murphy, J.C., 2025, Temporal changes in nutrient concentrations in the Lower Grand River and selected drainage basins, Missouri and Iowa, during the Mississippi River Basin Healthy Watersheds Initiative (2010–23): U.S. Geological Survey Scientific Investigations Report 2025–5099, 19 p., https://doi.org/10.3133/sir20255099.
ISSN: 2328-0328 (online)
Study Area
Table of Contents
- Acknowledgments
- Abstract
- Plain Language Summary
- Introduction
- Previous Investigations
- Purpose and Scope
- Site Description
- Streamflow and Water-Quality Data Collection
- Methods for Assessing Temporal Changes in Nutrient Concentrations
- Temporal Changes in Annual Mean Nutrient Concentrations at Mississippi River Basin Healthy Watersheds Initiative Sites
- Temporal Changes in Flow-Adjusted Nutrient Concentrations at Mississippi River Basin Healthy Watersheds Initiative Sites
- Temporal Changes in Annual Flow-Normalized Concentrations at Long-Term Sites
- Nutrient Dynamics Within the Lower Grand During the Mississippi River Basin Healthy Watersheds Initiative
- Nutrient Dynamics in the Grand River and Similar Nearby Tributaries During the Mississippi River Basin Healthy Watersheds Initiative
- Summary
- References Cited
- Appendix 1. Supplemental Data for Selected Sites in Missouri and Iowa
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Temporal changes in nutrient concentrations in the Lower Grand River and selected drainage basins, Missouri and Iowa, during the Mississippi River Basin Healthy Watersheds Initiative (2010–23) |
| Series title | Scientific Investigations Report |
| Series number | 2025-5099 |
| DOI | 10.3133/sir20255099 |
| Publication Date | November 26, 2025 |
| Year Published | 2025 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Publisher location | Reston, VA |
| Contributing office(s) | Central Midwest Water Science Center |
| Description | Report: vii, 19 p.; 5 Linked Tables; Data Release; Dataset |
| Country | United States |
| State | Iowa, Missouri |
| Other Geospatial | Lower Grand River |
| Online Only (Y/N) | Y |
| Additional Online Files (Y/N) | Y |