Abstract: Based on Google Earth Engine (GEE) remote sensing cloud computing platform and Landsat TM, ETM+ and OLI satellite image data, a comprehensive water body identification algorithm with multiple indices such as Modified Normalized Difference Water Index (MNDWI), Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) was used to extract the area of lakes larger than 1 km² in the Three-River Headwaters region (source region of the Yangtze River, the Yellow River, and the Lancang River) from 1990 to 2020. In association with meteorological, glacier cataloguing and permafrost distribution data, the changes of lake area along with their influencing factors were analyzed. The findings of the study reveal a 15% increase in the overall lake surface area from 10 811.8 km² to 12 449.53 km², with 46 new lakes in the Three Rivers area since 1990. Specifically, the increase in lake area differed across sources, with more visible changes observed in the Yangtze River source area (29%) compared to the Yellow River source area (10%). Rising average temperature and increased precipitation were identified as the primary factors behind the increase in lake area. Specifically, increasing temperature caused glacier retreat and permafrost degradation, resulting in a faster increase in the area of glacier-replenished lakes and lakes located in permafrost areas. Precipitation was more closely related to the increase of lake area in the Yellow River source area.

Key words: Three-Rivers Headwaters, GEE remote sensing cloud computing platform, lake area, dynamic changes of lake, climate change