Simulation study of reservoir water environment based on Mike21-taking Baisha reservoir as an example

Abstract

This study aims to simulate the reservoir area by constructing a coupled model to analyze the variations in the water flow field and the migration patterns of pollutants in the Baisha Reservoir under different flow increments. One of the key challenges in this process is selecting an appropriate model and calibrating its parameters. The MIKE21 hydrodynamic-water quality coupled model was employed to simulate the reservoir area, with extensive experimental calibration of the HD and Ecolab models' parameters based on the actual conditions of Baisha Reservoir. The performance of the models was evaluated, and the results indicated a high level of reliability. In the Ecolab model, three commonly used water quality indicators—BOD, NH₃-N, and NO₃—were considered for simulation and analysis. To examine the changes in the water flow field under different flow increments, three distinct flow increment scenarios were tested. The results showed that the best simulation performance occurred when the flow increment was 30 %, with BOD improvement of 51.02 %, NH₃-N improvement of 26.31 %, and NO₃ improvement of 37.13 %. Furthermore, an ESN model was developed to predict future water quality changes in Baisha Reservoir. The accuracy of the ESN model was validated using the water quality simulation results from Scenario 3, yielding an average relative error of 3.26 %. The water quality concentrations predicted under this scenario were significantly lower than the initial concentrations, providing practical insights into addressing issues related to water quantity and quality in the reservoir.