|Shields Jr, Fletcher|
Submitted to: International Hydro-Science & Engineering International Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/10/2005
Publication Date: 9/19/2005
Citation: Chao, X., Jia, Y., Shields Jr, F.D., Wang, S.Y. 2005. Development and application of a three dimensional water quailty model for a shallow oxbow lake. International Hydro-Science & Engineering International Proceedings. National Center for Computational Hydroscience and Engineering. The University of Mississippi. CD-ROM. Interpretive Summary: Lakes in agricultural watersheds sometimes have water quality problems due to soil eroded from surrounding fields that enters the lake with runoff. For example, water made turbid by suspended sediment will transmit less light to lower levels, hindering photosynthesis by simple plants (algae). Various best management practices (BMPs) may be used by farmers to reduce the amount of fine sediment leaving agricultural lands, but it is difficult to predict how much water quality improvement will follow a given BMP application. A computer program to simulate lake water quality was developed to address this need. The program was tested using simple, hypothetical conditions, and then was adjusted to match actual conditions in Deep Hollow Lake, an oxbow lake surrounded by fields in the Mississippi Delta. Computer outputs were compared with weekly water quality measurements. The computer program reproduced observed levels of chlorophyll with reasonable accuracy, showing that reduction of fine sediment entering the lake triggered more desirable conditions. These results provide a foundation for developing better tools for predicting the benefits of BMPs.
Technical Abstract: A three-dimensional numerical model was developed for simulating the concentration of water quality constituents. Four interacting systems were simulated, including phytoplankton dynamics, nitrogen cycle, phosphorus cycles, and dissolved oxygen balance. The effects of suspended and bed sediment on the water quality were also considered. The model was tested using analytical solutions for the transport of non-conservative substances in open channel flow, then calibrated and applied to a shallow oxbow lake to simulate the concentration of phytoplankton (as chlorophyll) and nutrients. The simulated trends and magnitudes of water quality constituents were generally in good agreement with field observations.