AN Lesheng, LIU Chun, FAN Zhongya, LIAO Kaihua, WANG Wencai, WANG Nan
To explore water level variations and their dynamic influence on the water quality of Huayang Lakes, the water level from 1967 to 2023 and water quality from 2015 to 2023 were analyzed using the Mann-Kendall trend test, box plots, and violin plots. The results show a notable hydrological rhythm of water level alternation between dry and flood seasons in Huayang Lakes, with an average water level of 12.82 m and a monthly range of 11.21-17.24 m. Since 2017, the water level of Huayang Rivers has shown a decreasing trend of -0.02 m/a. Total phosphorus (TP) has become the primary pollutant. The TP concentrations in Longgan Lake (the largest lake) during the dry, rising, flood, and retreating seasons from 2015 to 2023 were 0.083, 0.061, 0.050, and 0.059 mg/L, respectively. The effect of water level on TP was mainly observed during the low-water period. When the water level in the dry season rose to 12.25 and 13.00 m, the percentage of TP exceeding 0.1 mg/L in Longgan Lake decreased to 55.8% and 33.3%, respectively. During the dry season, wind and wave disturbances caused the release of endogenous phosphorus in Huayang Lakes. This led to drastic fluctuations in TP concentration, reducing the correlation between water level and TP. When external control is limited, the water level during the dry season should be maintained between 12.25 and 13.0 m. Additionally, it is necessary to accelerate the restoration of submerged macrophyte species (such as Hydrilla verticillata and Vallisneria natans) in the Huayang Rivers.