Numerical modeling of the Xiangxi River algal bloom and sediment-related process in China

A three-dimensional unstructured mesh eco-dynamic model was developed to simulate temporal and spatial variations in water quality with respect to phytoplankton, nutrients, dissolved oxygen, and suspended sediment, based on the ELcirc model. Four major interacting systems were simulated, including phytoplankton dynamics, nutrient cycles, dissolved oxygen balance, and suspended sediment. The effects of suspended and bed sediment on water quality processes were also considered. The model was applied to simulate algal bloom processes in the Xiangxi River (XXR), a tributary of the Yangtze River that was affected by the impounding of the Three Gorges Project. The model was calibrated and verified by field data during the XXR algal blooms. The simulated time serial concentrations of phytoplankton (chlorophyll) and nutrients were generally consistent with field observations. Sensitivity studies were then conducted to assess the impacts of varying inlet discharges, suspended sediment loads, and nutrient loading on the chlorophyll concentration of algae.