Numerical modeling of water diversion impacts on water quality improvement in Lake Dianchi

Abstract

A coupled hydrodynamic-water quality model was employed to investigate water quality improvement in Waihai of Lake Dianchi under different water diversion scenarios, including different volumes, inflow/outflow locations, and seasonal allocations. The accuracy of coupled model was reasonably validated against observed data on water level and temperature, total phosphorus (TP), total nitrogen (TN), dissolved oxygen (DO) and chlorophyll-a (Chl-a) concentrations. Further analysis reveals water diversion significantly improves Waihai's water quality. In northern Waihai, the annual average TP and TN concentrations decrease by 27.2% and 26.1%. The average Chl-a concentration decreases by 36.8% during wet season. Increasing water diversion volume emerges as the most effective strategy for improving water quality. Designating the Panlong River as the inlet and the Jiezhi Gate as the primary outlet for diverted water proves more advantageous in reducing TP, TN, and Chl-a concentrations. Concentrating diverted water during wet season leads to more substantial reductions in Chl-a concentrations.