Study region: Xinjiang Study focus: Lakes play a crucial role in the extensive mountain-oasis-desert ecosystems of Xinjiang, exhibiting a high dependency on meltwater from mountainous regions, thus being extremely sensitive to climatic changes. Due to its geographic remoteness and underdeveloped infrastructure, Xinjiang lacks an understanding of the quantitative contributions of the primary factors driving lake changes and the underlying mechanisms. This study used Landsat remote sensing images and topographic data to establish an empirical equation for area-water storage changes, monitored and calculated the lake surface area (LSA) and lake water storage change (LWSC) of all lakes larger than 1 km2 (324 in total) in Xinjiang from 1990 to 2022. The major factors influencing changes in LWSC were quantitatively assessed based on the lake water balance. New hydrological insights: From 1990-2022, the number of lakes in Xinjiang increased by approximately one quarter (59 lakes), with the LSA expanding by about one third. LWSC has significantly expanded, with maximum and minimum LWSC (maxLWSC and minLWSC) increasing by 40.98 and 38.37 Gt, respectively. Notably, the lakes in South Xinjiang approximately doubled in LWSC. These lakes are primarily distributed in the southern mountainous areas, which are less affected by human interference, while the plain areas are influenced by human activities and annual ecological water deliveries. In this region, both the interannual variations of maxLWSC and minLWSC exhibit considerable fluctuations. By establishing a lake water balance for nearly 80 % of the expanded water volume in Xinjiang, it was found that the expansion is mainly controlled by groundwater recharge (96.11 %) and lake surface evaporation (-90.63 %). This study systematically analyzed the changing characteristics of lakes in Xinjiang and provided important scientific evidence for a deeper understanding of the lake water cycle processes.