| The two-dimensional hydrodynamic and eutrophication model of a Pumped-Storage Reservoir was developed based on MIKE21 ECOLab, to investigate the methods of improving calibration efficiency, and to analyze the spatiotemporal pattern of residence time, nitrogen, phosphorus, and chlorophyll-a in the pumped-storage reservoir. The results indicate that the calibration sequence for 9 state variables in the ECOLab module is: BOD>PO43-=NH4+>NO2->NO3->Chl-a=FC=TC>DO，and 11 of the 41 parameters are primary calibration parameters. The model satisfactorily represented the hydrodynamic and water quality processes of the reservoir, by validating with actual measurement data from 2022. Using this model, the simulated average residence time of water in the reservoir is 9 days, given an annual water diversion volume of 490 million cubic meters. The residence time along the mainstream direction is relatively shorter, but it increases towards both sides, inversely proportional to the distance from the shore, indicating a high spatial variability. In reservoir bays, the residence time notably increases, reaching a peak of over 200 days. Based on observed water quality data of pumping water over the past five years, the simulation results indicate that the annual average concentrations of inorganic nitrogen, inorganic phosphorus, and chlorophyll-a are 0.75 mg/L, 1.93 μg/L, and 20.93 μg/L, respectively. Influenced by seasonal variations in non-point source pollution inputs from the Dongjiang River basin, the concentrations of nitrogen, phosphorus, and chlorophyll-a are higher during the wet season compared to the dry season. In regions with shorter residence times, nitrogen and phosphorus concentrations tend to increase, while chlorophyll-a concentrations tend to decrease. The outcomes of this study provide important information for model construction and eutrophication control in pumped-storage reservoirs. |
