Strategies for Managing Environmental Flows Based on the Spatial Distribution of Water Quality: A Case Study of Baiyangdian Lake, China.

Water shortages and deterioration of water quality become more serious as a result of industrial development and urbanization, but both can be mitigated by optimal management of environmental flows. In this paper, we used Baiyangdian Lake as a case study of this form of management. We divided the lake into 13 sub-areas using GIS software, and analyzed water-quality processes in each sub-area using an eutrophication model based on the WASP 7 software. The model considered the dissolved oxygen content, the nitrogen and phosphorus cycles, and phytoplankton growth. We used monitoring data for Baiyangdian Lake to parameterize and validate the model. Using the model, we then analyzed water quality variations for different non-point-source pollution load scenarios and artificial water release scenarios to reveal the relationships between water quality and these factors. We found that return water such as industrial wastewater and domestic sewage with a large organic load worsened eutrophication, whereas reducing pollutant loads, transferring water into the lake, or a combination of the two approaches improved water quality. The detailed spatial distribution of water quality supplied key information to support further analysis of ecological water demand and water allocation. Our simulation revealed environmental flows of 3.87x10⁸, 3.70x10₈, and 3.23x10₈ m³/a, respectively, for scenarios with pollutant load reductions of 30, 50, and 90% under various water-release strategies. On this basis, we propose optimal water quality management strategies for Baiyangdian Lake to improve its water environment. [ABSTRACT FROM AUTHOR]