Author(s): Lingjiang Lu; Yongcan Chen; Zhaowei Liu

Linked Author(s):

Keywords: Nansi Lake; Hydrodynamic simulation; Water quality; South-to-North Water Diversion Project

Abstract: The Nansi Lake is one of the key storage reservoirs in the Eastern Route of the South-to-North Water Diversion Project (SNWDP-ER) in China, which was divided into the Upper Lake and Lower Lake by the Erji Dam. Due to water diversion being conducted only during the dry season, Nansi Lake experiences periodic flow reversals during diversion and non-diversion periods, leading to frequent water exchange between the Upper and Lower Lakes. A comprehensive hydrodynamic and water quality simulation of Nansi Lake and its connected canals is essential for understanding water quality evolution and variations during different operational periods. Based on the T-UWMM model for complex water systems, a multi-region solver was constructed to sequentially simulate the Upper and Lower Lakes. An internal boundary mechanism was implemented in the Erji Dam to enable the exchange of flow and substance concentrations between the two lakes in order to establish an integrated numerical model for Nansi Lake. Numerical simulations of the hydrodynamic and water quality conditions in Nansi Lake for 2021 showed that during the water diversion period, water stages were higher in the south, with flow moving south-to-north, while the opposite occurred during the non-diversion period, consistent with observed conditions. The water quality simulation revealed that the Lower Lake had slightly better water quality than the Upper Lake, suggesting that diverted water from the Lower Lake during the diversion period can improve the Upper Lake’s water quality, demonstrating a positive impact of SNWDP-ER. Additionally, water quality was more stable during the diversion period, whereas CODMn concentrations fluctuated significantly during the non-diversion period, with tributary pollution being more pronounced in the latter, emphasizing the importance of tributary management. These findings provide a quantitative basis for analyzing water flow and material exchange processes between the Upper and Lower Lakes and offer theoretical support for operational management and water quality improvement in the Nansi Lake Basin.

DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P1728-cd

Year: 2025