Hydrodynamic features and water ecology improvement of Yuehai Lake based on ecological water diversion

Abstract

To mitigate lake eutrophication, this paper collects the relevant data and monitors the water of Yuehai Lake, the seat of Ningxia Hui Autonomous Region, China, and constructs an eco-dynamics model of the lake water. Then, the alternating direction implicit (ADI) method was adopted to discretely solve the hydraulic equation and the convective diffusion equation, and the model parameters were calibrated and verified against the monitoring data of hydrology, meteorology, and water quality from May 2018 to October 2019. After that, the laws of nutrient transmission, diffusion, and spatiotemporal distribution were obtained through simulation with such factors as chemical oxygen demand (COD), ammonia nitrogen, total nitrogen, total phosphorus, and chlorophyll a; the simulation results agree well with the measured data. Based on the actual situation of the lake, a scheme was prepared to change the hydrodynamic condition from three aspects: replenished water flow, rainfall, and wind-driven circulation. The results show that the flow field of Yuehai Lake is not greatly affected by the first two factors, but determined by wind-driven circulation. The proposed scheme for ecological water diversion is expected to effectively improve the water quality of Yuehai Lake.