Extreme drought affects lake water quality, quantity, morphometry: Evidence from China’s largest fresh water lake under the 2022 global drought

Extreme drought poses a significant threat to humanity. In the summer of 2022, the world experienced the worst drought in recent years, with a precipitation deficit and an abnormal high temperature, profoundly affecting human life and the aquatic environment. However, the drought influence on large freshwater lakes remains unclear. In this study, we selected China’s largest freshwater lake (Poyang Lake) as the research object and investigated the lake water area, quantity, lake morphology and water quality in 2018 (normal season) and 2022 (extreme drought period). Results showed that standardized precipitation index (SPI), standardized runoff index (SRI) and standardized precipitation-evapotranspiration index (SPEI) reached moderate to severe drought in the summer of 2022. From 2018 to 2022, lake water area decreased (1789.62 km²), water quantity reduced (15.40 × 10⁹ m³) and lake shoreline decreased (2923.70 km). The shoreline development index, size ratio and energy factor decreased by 4.87, 198.53 m and 963.60, specifically. The dynamic ratio, relative depth and Schindler’s ratio increased by 1457.10, 0.04 and 13.48 m⁻¹, respectively. The water chemical indicators varied significantly in two years and the water hydrochemical types changed from SO₄·Cl − Ca·Mg type and HCO₃ − Ca·Mg type to SO₄·Cl − Ca·Mg type from 2018 to 2022. Water-rock interaction, alternating cation adsorption and anthropogenic influence on water quality represented different patterns in two periods. Our findings demonstrate significant differences in water resources and quality between common and extreme drought conditions in China’s largest fresh water lake, which can inform research on climate change effects on international large freshwater lakes.