Inundation impacts and risk assessment of Qinghai Lake from 2004 to 2024

To understand the submerged areas and impacts of expansion of Qinghai Lake and to improve early-warnings of lakeside inundation and risk-avoidance strategies, this study quantifies the inundation patterns, environmental effects of rising water levels, and predictions of future flood risk through geospatial analyses (normalized difference water index and digital elevation model simulations) of integrated Landsat TM/OLI imagery (2004-2024), elevation data, land-use maps, and regional meteorological and hydrological records. From 2004 to 2024, the lake level rose by 4.2 m while the surface area increased at 19.3 km2 per year, permanently submerging 197.3 km2 of grassland and 131.7 km2 of sandy land. The inundation frequency along the shoreline strongly depends on elevation, being high in the Shadao area on the eastern shore and moderate-to-low in the mouths of Buha and Shaliu Rivers on the northwestern shore. Scenario simulations indicated that the expanding lake area does not affect the surrounding highways or railways over the short-term. However, if the water level reaches 3202 m, it will threaten a section of the G109 national highway on the southern shore, and if it rises to 3204 m, it may inundate the Qinghai-Xizang railway on the northwestern shore.