Impact of Artificial Water Replenishment on Spatiotemporal Distribution of Local Water Renewal Time in West Lake

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Abstract
Water replenishment projects (WRP) are widely regarded by lake managers as an effective method for ecological restoration. But studies on multiple water receiving lakes indicate that multi-source water supplementation may exacerbate spatial heterogeneity in water quality. The primary causes are the uneven quality of external water sources and the morphology of the lakes themselves. Hangzhou’s West Lake, which relies on a single water source, also exhibits ecological differences between its lake areas. To explain this phenomenon from a hydrodynamic perspective, this study employs Delft3D model simulations to determine the spatiotemporal heterogeneity in the impact of artificial water replenishment on local water renewal times (LWRT) across different lake areas. The results indicate that, compared to natural conditions, WRP shortens the typical LWRT at most sites in West Lake and reduces the seasonal variation amplitude of LWRT. The WRP impedes local water exchange capacity in certain lake areas during specific months, potentially creating stagnant zones. Moreover, the spatiotemporal heterogeneity of its impact on West Lake’s hydrodynamic conditions amplifies differences in flow rhythms between lake regions, leading to fragmented water movement. This may ultimately compromise the integrity of the lake’s overall ecological environment. Managers of receiving lakes should consider increasing monitoring frequency and the number of monitoring stations to address more complex water quality conditions. Future designers of WRPs should incorporate the prevention of fragmented hydrodynamic conditions as an evaluation criterion in diversion scheme planning. This study provides references and evidence for lake ecological management and research on the impact mechanisms of WRPs on shallow lakes.
Funding Information
  • National Natural Science Foundation of China (61991454)
  • National Key Research and Development Program of China (2023YFC3107605)
  • Oceanic Interdisciplinary Program of Shanghai Jiao Tong University (SL2022ZD206)
  • Scientific Research Fund of Second Institute of Oceanography, MNR (SL2302)

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