Location: Water Quality and Ecology ResearchTitle: The impact of agricultural activities on water quality in oxbow lakes in the Mississippi Delta Author
Submitted to: International Conference on Hydroscience and Engineering (ICHE)
Publication Type: Proceedings
Publication Acceptance Date: 7/2/2014
Publication Date: 9/28/2014
Citation: Chao, X., Locke, M.A., Jia, Y., Lizotte Jr, R.E. 2014. The impact of agricultural activities on water quality in oxbow lakes in the Mississippi Delta. International Conference on Hydroscience and Engineering (ICHE). 2014, Hamburg, Bundesanstalt fur Wasserbau ISBN 978-3-939230-32-8. 1155 pp. (Conference Proceedings). Interpretive Summary: As we continue to improve our understanding of how agricultural activity contributes to nonpoint source pollutants such as sediments nutrients and pesticides, the use of lake models based on field measurements can be a powerful tool to help assess the long-term effectiveness of agricultural conservation practices. The study used a new 3-dimensional lake water quality model validated from long term measured lake data to analyze suspended sediment loads and their effects on algae and nutrients before and after implementation of conservation practices. The newly improved and validated 3-dimensional lake water quality model was able to better simulate real water quality conditions with better agreement with measured field observations in the lake and allow improved assessments of the effectiveness of agricultural conservation practices using this model. These results are of interest to regulatory and other agencies and farming stakeholders by providing additional information to improve and sustain lake water quality and overall environmental quality using conservation practices.
Technical Abstract: In the Mississippi Delta, agricultural activity is a major source of nonpoint source (NPS) pollutants. Sediment, nutrients and pesticides have been considered as priority NPS pollutants and greatly affect the water quality in this area. The impacts of agricultural activities on water quality in oxbow lakes in this area were assessed based on field measurements and numerical model. The long term measured data was used to analyze the concentration distribution of sediment in the lakes pre- and post- implementation of BMPs installed in the watersheds. Three major sediment-associated water quality processes were studied, including the effect of sediment on the growth of phytoplankton, the adsorption-desorption of nutrients by sediment and the release of nutrients from bed sediment layer. The newly improved and validated 3D water quality model was used to simulate the water quality constituents with considering more realistic 3D mixing in the oxbow lakes by wind shear on water surface. As a result, the simulated concentration of chlorophyll and nutrients were generally in better agreement with field observations. This study confirms that the water quality of the lakes was sensitive to suspended sediment concentrations. Of equal importance, the capability of simulating various physical and chemical rate processes, such as growth, death, settling, degradation, etc. in the water have been added in the computational model. Therefore, when watershed water quality is concerned, one has to consider factors such as sediment loadings and agriculture activities. And, the effectiveness of the BMP can be assessed by newly improved 3D water quality computational model.