Numerical modeling of water quality and sediment related processes

A three-dimensional water quality model (CCHE3D_WQ) was developed for simulating temporal and spatial variations of water quality with respect to phytoplankton, nutrients, and dissolved oxygen. Four major interacting systems were simulated, including phytoplankton dynamics, nitrogen cycle, phosphorus cycle, and dissolved oxygen balance. The effects of suspended and bed sediment on the water quality processes were also considered. The model was verified using analytical solutions for the transport of non-conservative substances in open channel flow, and then calibrated and validated by applying it to the study of the water quality of a natural shallow oxbow lake. The simulated time serial concentration of phytoplankton (as chlorophyll) and nutrients were generally in good agreement with field observations. Sensitivity studies were then conducted to demonstrate the impacts on water quality due to varying nutrients and suspended sediment loads to the chlorophyll concentration.