Assessment of Long-term Trends in Water Level and Water Volume Changes in Erhai Lake, Southwest China (1987–2020)

Understanding the dynamic changes of lake water level and water volume is conducive to the protection and restoration of the environment of a lake. Taking Erhai Lake in Southwest China as the study area, this research quantifies and analyzes the long-term variation trends of water level and water volume from 1987 to 2020 based on multi-source data and an integrated approach. The results show that annual water level and annual water volume of the Erhai Lake generally show a downward trend, and fluctuate between years. Annual water level and annual water volume of the Erhai Lake increased most rapidly in 1989-1990, and decreased most rapidly in 2013-2014. Compared with 1987, annual water level and annual water volume of the Erhai Lake decreased by 2.14 m and 0.41 billion m³ respectively in 2020. In 1991, the Erhai Lake had the most abundant water resources, with annual water level and annual water volume of 1968.98 m and 4.39 billion m³; in 2016, the Erhai Lake had the most scarce water resources, with annual water level and annual water volume of 1961.05 m and 2.89 billion m³. The results from this study provide basic data for the rational use of water resources, the management and protection of the environment of the Erhai Lake.