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Eutrophication of lakes due to increased loading of nutrients negatively affects water quality, warranting worldwide efforts to reduce the limiting nutrient in most lakes, phosphorus (P). Government regulations on excess nutrient loads entering the James River Arm (JRA) of Table Rock Lake, Missouri began in 2001 with upgrades at a major sewage treatment plant (STP). The present study aims to quantify the spatial and temporal distribution of sediment P in the James River Basin by (1) quantifying present sediment-P concentrations in the basin, (2) describing the spatial patterns of sediment-P reduction, and (3) investigating the link between upstream sediment and P sources and JRA sediment-P response. Lake sedimentation zones are identified based on physical and chemical sediment characteristics and lake morphometry. Sediment-P concentrations are highest immediately downstream of the STP (620-1,190 ppm) and in the JRA (370-1,580 ppm) and are lower in the James River (170-640 ppm). Sediment-P concentrations in the JRA are strongly correlated to depth and Mn (r2 = 0.92). Sediment-P concentrations have decreased downstream of the STP since 2001, ranging from 14-58% in stream sediments, and 31-36% in the JRA. Lake sediment-P reductions are greatest in deeper areas of the JRA. Concentrations of A1 have decreased by 9-70% in the James River and Wilson's Creek, and have increased in the JRA by 9-34%, potentially reflecting the influence of STP treatment procedures or variable sediment sources on sediment geochemistry. Nonpoint P may have increased since 2001, warranting future attention.
The Chesapeake Bay is North America's largest and most biologically diverse estuary, as well as an important commercial and recreational resource. However, excessive amounts of nitrogen, phosphorus, and sediment from human activities and land development have disrupted the ecosystem, causing harmful algae blooms, degraded habitats, and diminished populations of many species of fish and shellfish. In 1983, the Chesapeake Bay Program (CBP) was established, based on a cooperative partnership among the U.S. Environmental Protection Agency (EPA), the state of Maryland, and the commonwealths of Pennsylvania and Virginia, and the District of Columbia, to address the extent, complexity, and sources of pollutants entering the Bay. In 2008, the CBP launched a series of initiatives to increase the transparency of the program and heighten its accountability and in 2009 an executive order injected new energy into the restoration. In addition, as part of the effect to improve the pace of progress and increase accountability in the Bay restoration, a two-year milestone strategy was introduced aimed at reducing overall pollution in the Bay by focusing on incremental, short-term commitments from each of the Bay jurisdictions. The National Research Council (NRC) established the Committee on the Evaluation of Chesapeake Bay Program Implementation for Nutrient Reduction in Improve Water Quality in 2009 in response to a request from the EPA. The committee was charged to assess the framework used by the states and the CBP for tracking nutrient and sediment control practices that are implemented in the Chesapeake Bay watershed and to evaluate the two-year milestone strategy. The committee was also to assess existing adaptive management strategies and to recommend improvements that could help CBP to meet its nutrient and sediment reduction goals. The committee did not attempt to identify every possible strategy that could be implemented but instead focused on approaches that are not being implemented to their full potential or that may have substantial, unrealized potential in the Bay watershed. Because many of these strategies have policy or societal implications that could not be fully evaluated by the committee, the strategies are not prioritized but are offered to encourage further consideration and exploration among the CBP partners and stakeholders.
Using the Soil and Water Assessment Tool (SWAT) for large-scale watershed modeling could be useful for evaluating the quality of the water in regions that are dominated by nonpoint sources in order to identify potential "hot spots" for which mitigating strategies could be further developed. An analysis of water quality under future scenarios in which changes in land use would be made to accommodate increased biofuel production was developed for the Missouri River Basin (MoRB) based on a SWAT model application. The analysis covered major agricultural crops and biofuel feedstock in the MoRB, including pasture land, hay, corn, soybeans, wheat, and switchgrass. The analysis examined, at multiple temporal and spatial scales, how nitrate, organic nitrogen, and total nitrogen; phosphorus, organic phosphorus, inorganic phosphorus, and total phosphorus; suspended sediments; and water flow (water yield) would respond to the shifts in land use that would occur under proposed future scenarios. The analysis was conducted at three geospatial scales: (1) large tributary basin scale (two: Upper MoRB and Lower MoRB); (2) regional watershed scale (seven: Upper Missouri River, Middle Missouri River, Middle Lower Missouri River, Lower Missouri River, Yellowstone River, Platte River, and Kansas River); and (3) eight-digit hydrologic unit (HUC-8) subbasin scale (307 subbasins). Results showed that subbasin-level variations were substantial. Nitrogen loadings decreased across the entire Upper MoRB, and they increased in several subbasins in the Lower MoRB. Most nitrate reductions occurred in lateral flow. Also at the subbasin level, phosphorus in organic, sediment, and soluble forms was reduced by 35%, 45%, and 65%, respectively. Suspended sediments increased in 68% of the subbasins. The water yield decreased in 62% of the subbasins. In the Kansas River watershed, the water quality improved significantly with regard to every nitrogen and phosphorus compound. The improvement was clearly attributable to the conversion of a large amount of land to switchgrass. The Middle Lower Missouri River and Lower Missouri River were identified as hot regions. Further analysis identified four subbasins (10240002, 10230007, 10290402, and 10300200) as being the most vulnerable in terms of sediment, nitrogen, and phosphorus loadings. Overall, results suggest that increasing the amount of switchgrass acreage in the hot spots should be considered to mitigate the nutrient loads. The study provides an analytical method to support stakeholders in making informed decisions that balance biofuel production and water sustainability.
"The Great Lakes hold over 20% of the earth's surface fresh water. Due to intense agricultural practices, the ecosystems of the Great Lakes have deteriorated. As the water pollution caused by agricultural activity is non-point source pollution, it is much harder to assess the pollution as compared to point sources of pollution where we can identify the sources of pollution easily. With the help of mathematical modeling, we can make a reasonable assessment of such pollution as well as provide different options (best management practices (BMPs)) for mitigating the problem. The Soil & Water Assessment Tool (SWAT) was selected to model the hydrology of the Gully Creek watershed in Ontario. SWAT is a watershed scale, continuous simulation model. Available data were used to calibrate and validate the model, and the Nash-Sutcliffe Efficiency (NSE), Percent Bias (PBIAS), and Coefficient of Determination (R2) statistics were used to evaluate the model's performance for simulating flow, sediment yield, and phosphorus yield. Due to the scarcity of observed data, calibration was performed for flow, sediment, and phosphorus between the start of 2011 and 2013. Flow calibration of the model was found to be satisfactory, with an NSE of 0.5, a PBIAS of 24.8%, and an R2 of 0.53. Calibration of sediment yield did not provide satisfactory results for NSE, PBIAS, and R2, with values of -0.75, 33.8%, and 0.14, respectively. Additionally, total phosphorus load was tested based on the calibration results, and it too did not provide satisfactory results. A "no BMP" scenario was created to evaluate the effectiveness of current and potential BMPs. "Retire to Forest" and "Retire to Pasture" reduced the total phosphorus load the most. Compared to the present practice, "Retire to forest" reduced phosphorus loss by 90%, compared to 73% under "pasture retirement." Conservation tillage BMPs could reduce the phosphorus burden. No-till BMP reduced phosphorus by 23% annually and 16% during the growing season, while minimum tillage reduced it by 8% annually and 1% during the non-growing season. Vegetated filter strips (VFS) at field boundaries reduced phosphorus loss (61%). The cover crop BMP was found to reduce annual phosphorus loss by 13%, whereas during spring, it shows a considerable reduction (29%). This study demonstrates how BMPs and hydrological modeling using SWAT will assist planners in controlling soil and water pollution at the watershed scale. The current study demonstrates conservation methods and offers practical guidance on how to choose the best BMPs for agricultural watersheds"--