The water level change and its attribution of the Qinghai Lake from 1960 to 2020

Study region: The Qinghai Lake basin on the Qinghai-Tibetan Plateau. Study focus: The abrupt rise of the water level of the Qinghai Lake after 2004 has garnered significant attention. Combining remote sensing and observed data, this study estimated the longterm variations in the water area and volume of the lake. In order to explore the factors contributing to the fluctuation in water level, the study developed annual and inter-annual water budgets for two time intervals: 1960 to 2004 and 2004 to 2020. Additionally, a hydrological model was implemented in the Buha River Basin, to gain further insight into the increased runoff and the impact of frozen soil. New hydrological insights for the region: The study found that the rise in lake level since 2004 was primarily driven by increased runoff, followed by increased precipitation, and decreased evaporation. Furthermore, water budgets were established for the freezing period (November to March of the next year) and the thawing period (April to October), respectively. The results revealed that the contribution of surface runoff during the thawing period was significantly larger at 68.20 % compared to 15.64 % during the freezing period, which is consistent to the conclusions of model simulation suggested. These findings suggest that the degradation of frozen soil in the Qinghai Lake Basin was a significant factor positively influencing surface runoff, with its impact intensifying after 2004.