Nutrient and Suspended-Sediment Trends in the Missouri River Basin, 1993-2003

Abstract

The U.S. Geological Survey (USGS) is committed to providing the Nation with credible scientific information that helps to enhance and protect the overall quality of life and that facilitates effective management of water, biological, energy, and mineral resources (http://www.usgs.gov/). Information on the Nation's water resources is critical to ensuring long-term availability of water that is safe for drinking and recreation and is suitable for industry, irrigation, and fish and wildlife. Population growth and increasing demands for water make the availability of that water, now measured in terms of quantity and quality, even more essential to the long-term sustainability of our communities and ecosystems. The USGS implemented the National Water-Quality Assessment (NAWQA) Program in 1991 to support national, regional, State, and local information needs and decisions related to water-quality management and policy (http://water.usgs.gov/nawqa). The NAWQA Program is designed to answer: What is the condition of our Nation's streams and ground water? How are conditions changing over time? How do natural features and human activities affect the quality of streams and ground water, and where are those effects most pronounced? By combining information on water chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide science-based insights for current and emerging water issues and priorities. From 1991-2001, the NAWQA Program completed interdisciplinary assessments and established a baseline understanding of water-quality conditions in 51 of the Nation's river basins and aquifers, referred to as Study Units (http://water.usgs.gov/nawqa/ studyu.html). In the second decade of the Program (2001-2012), a major focus is on regional assessments of water-quality conditions and trends. These regional assessments are based on major river basins and principal aquifers, which encompass larger regions of the country than the Study Units. Regional assessments extend the findings in the Study Units by filling critical gaps in characterizing the quality of surface water and ground water, and by determining status and trends at sites that have been consistently monitored for more than a decade. In addition, the regional assessments continue to build an understanding of how natural features and human activities affect water quality. Many of the regional assessments employ modeling and other scientific tools, developed on the basis of data collected at individual sites, to help extend knowledge of water quality to unmonitored, yet comparable areas within the regions. The models thereby enhance the value of our existing data and our understanding of the hydrologic system. In addition, the models are useful in evaluating various resource-management scenarios and in predicting how our actions, such as reducing or managing nonpoint and point sources of contamination, land conversion, and altering flow and (or) pumping regimes, are likely to affect water conditions within a region. Other activitie...

Long-Term Agroecosystem Research in the Central Mississippi River Basin: SWAT Simulation of Flow and Water Quality in the Goodwater Creek Experimental Watershed

“…Claypan soils are unique because of their low percolation and high runoff potential. Claypan soils are defined by a naturally occurring, subsurface argillic clay layer with an abrupt increase in clay content, from 15 to 30% in the topsoil to 50 to 60% in the clay layer (Soil Science Glossary Terms Committee, 2008). Additionally, the claypan has a very low saturated hydraulic conductivity when wet, but cracks form during extensive dry periods and allow subsequent runoff to infiltrate throughout the soil profile and recharge the aquifer.…”

Pre‐ and post‐impoundment nitrogen in the lower Missouri River

“…Sprague et al . () calculated statistically significant, flow‐adjusted increases in total‐N concentrations at St. Joseph, Mo of 13% per year ( p = 0.0002) and 3.2% per year also was calculated at Hermann, Mo. ( p = 0.012) from 1997 through 2003.…”

“…(3.2% per year) computed by Sprague et al . () from 1997 through 2003. This higher rate of flow‐adjusted N increases at the middle station in the lower Missouri River indicates the reach between Omaha and St. Joseph is a larger source of nitrate than the reach from St. Joseph to Hermann, Mo.…”

“…The leveling off of nitrate‐N concentrations between 1993 and 2003 at Hermann was identified by Sprague et al . (), who calculated a small and statistically insignificant ( p = 0.19), flow‐adjusted, average decrease in nitrate‐N concentrations. However, flow‐adjusted and non‐flow‐adjusted nitrate‐N increases were large (5.5 to 12% per year) and significant from 2000 through 2008 at Omaha, St Joseph, and Hermann ( p < 0.02, Table ).…”

Modeling Variability and Trends in Pesticide Concentrations in Streams1

“…Parametric models tend to focus on relatively well‐behaved chemical constituents such as major ions, certain nutrients, or suspended sediment (for example, Langland et al. , 2004; Vecchia, 2005; Sprague et al. , 2006).…”