Concentrations Fluxes And Yields Of Nitrogen Phosphorus And Suspended Sediment In The Illinois River Basin 1996 2000

Knowledge about sediment yields is important in developing management strategies for fluvial systems. The effect of sediment must be considered in the design of river structures and in determining water quality for biotic systems. Changes in sediment transport regimes are difficult to understand or predict due to the complexity of factors that influence sediment flux in fluvial systems. Relationships about sediment source, sinks and transport have long been studied and many of these relationships have been quantitatively and qualitatively defined. However, due to the scarcity of long-term sediment records it is often difficult to test these relationships. This study examines one of these long-term suspended sediment records for the Mississippi River at East Dubuque, Illinois from 1943 to 1996. Daily suspended sediment concentrations from the United States Army Corps of Engineers station at East Dubuque were analyzed for the spring and summer months (March - August). Sediment concentrations were analyzed in terms of average concentration during different hydrologic events at the large basin scale. These events included the spring snowmelt runoff (low and high magnitude) and different intensity storm runoff (low, moderate and high). Additionally, peak sediment concentrations during storm runoff were also analyzed. The general trend for all of these analyses suggests a significant decrease in sediment concentrations from the 1940s to the 1990s. The strongest trends are found in high magnitude snowmelt runoff and in high and moderate magnitude storm runoff. Peak concentrations in storm runoff have decreased from about 1000 ppm in the l940s to about 200 ppm in the 1990s. Average concentrations have likewise decreased from about 200 ppm in the 1940s to 100 ppm in the 1990s. Changes in land management practices are identified as being the primary environmental factor influencing sediment concentrations.

The environmental impacts of agricultural non-point source pollution, due in part to the intensification of agriculture to meet the nutritional needs of a growing population, indicate a need for the further implementation of Best Management Practices (BMPs) that can mitigate soil erosion and reduce the export of sediment and nutrients to receiving waters. Water and Sediment Control Basins (WASCoBs) and cover crops are both considered effective in-field BMPs that have been utilized by landowners to reduce soil and nutrient losses from fields. While each of these BMPs has been individually researched for their impacts on soil and water quality, there is little existing research that examines the impact of WASCoBs paired with cover crops on water quality. This study compared four sub-watersheds on the same field near Atterberry, Illinois: 1) a basin drained by a WASCoB, 2) a basin drained by a WASCoB and planted with a cover crop, 3) a basin drained by an ephemeral gully and planted with a cover crop, and 4) a control basin drained by an ephemeral gully. Runoff samples were collected from these watersheds and analyzed for total phosphorus, dissolved reactive phosphorus (DRP), ammonium-nitrogen, nitrate-nitrogen, and total suspended solids (TSS). Nutrient and sediment concentrations were used along with the discharge and duration of runoff events in order to determine event loads for each watershed. The WASCoBs utilized in this study were able to trap 97.3-99.2% of total phosphorus, 84.3-94.4% of DRP, 51.4-78.6% of ammonium-nitrogen, 11.8-56.3% of nitrate-nitrogen, and 98.68-99.21% of TSS. The cover crop treatments in this study did not show a significant impact on water quality, which was likely attributed to poor establishment of the cover crop. These results suggest that early planting is critical for maximizing cover crops establishment and benefit. Reductions in nutrient and sediment loads in this study suggest that WASCoBs have the potential to reduce the discharge of nutrients and sediment to waterways, indicating that their continued implementation may help to accomplish water and soil conservation goals.

Completely revised and updated, Treatment Wetlands, Second Edition is still the most comprehensive resource available for the planning, design, and operation of wetland treatment systems. The book addresses the design, construction, and operation of wetlands for water pollution control. It presents the best current procedures for sizing these syste