Causes of continuous decline in water level of Fuxian Lake and quantitative evaluation of contributions of multiple factors in 2023

Abstract

[Objective] The persistent decline in the water level of Fuxian Lake has significantly impacted the ecological environment within its basin and the production and livelihoods in surrounding areas. Investigating the causes of this decline is crucial for protecting Fuxian Lake's ecosystem and realizing its socio-economic value.[Methods] A distributed hydrological model, Water and Energy Transfer Processes in Large River Basin(WEP-L), was applied to simulate the water resource volume of the Fuxian Lake Basin from 1956 to 2023. Based on the long-term average net water balance under natural conditions, the contributions of meteorological drought, the diversion of outflow from Xingyun Lake, water consumption, and external drainage to the reduction of Fuxian Lake's water volume in 2023 were quantified using observational data, contribution rate analysis, and the water balance equation.[Results] The result showed that:(1) the water level of Fuxian Lake generally showed a slow declining trend at a rate of 0.12 m·a^-1, with a drop of 1.6 m below the multi-year average water level.(2) From 1956 to 2023, the inflow into Fuxian Lake from the entire basin showed a declining trend. In 2023, the net water balance of Fuxian Lake was-111 million m³, a decrease of 204 million m³ compared with the 93 million m³ under the multi-year average natural conditions.(3) According to the calculation of the water balance equation, the contribution rate of reduced precipitation and increased lake evaporation caused by rising temperatures to the net water balance decline of Fuxian Lake was 65.7%, the contribution rate of the Xingyun Lake diversion project was 19.6%, and the contribution rate of water consumption and external drainage was 14.7%.[Conclusion] The decline in Fuxian Lake's water level is influenced by multiple factors. The study highlights the dominant role of climate change, providing a scientific basis for watershed managers to formulate water resource allocation strategies and holding great significance for ensuring the ecological security of Fuxian Lake.

Keywords

WEP-L model / water level decline / Fuxian Lake Basin / meteorological drought / water balance equation / contribution rate / parameter sensitivity / influencing factors