Simulation of pollution tracing for shallow lakes based on hydrodynamic and environmental capacity analysis: a case study on Lake Futou, China

This study employed the environmental fluid dynamics code model framework to construct a hydrodynamic-water quality model for Futou Lake, a typical shallow lake located in Hubei Province, China. Critical findings of this work were as follows: (1) tracer simulations indicate that pollutants discharged from the Gan He River, the main inflow river of Futou Lake, took approximately 45 days to reach the monitoring section at the center of the lake; (2) the spatial distribution of flow fields and water quality parameters in Futou Lake exhibited significant variability under different hydrological and meteorological conditions and were closely linked to hydrodynamic characteristics, flow velocity, water level and discharge; and (3) under the Class II water quality standard, the simulated environmental capacities for total phosphorus, ammonia nitrogen and chemical oxygen demand at the center of the lake were 0.18, 1.08 and 159.64 kt/a, respectively, in 2023. Among the major inflow rivers, Gan River contributed the highest pollutant load, and the required reduction in total phosphorus and chemical oxygen demand loads were quantified. These results provide a scientific basis for understanding the spatiotemporal hydrodynamic-water quality dynamics and supporting aquatic environment management strategies in Futou Lake and similar shallow lake systems.