Surface water dynamics and driving factors in the Huangshui River Basin of the Xining-Haidong Corridor in China from 2000 to 2024 based on Google Earth Engine

Sustaining surface water in arid mountain-valley corridors has become increasingly difficult under a warming-wetting climate and urbanization. Focusing on the Huangshui River Basin in the Xining-Haidong Corridor of China, this study used Google Earth Engine (GEE) to process Landsat 5/7/8/9 surface reflectance imagery to reconstruct open-water dynamics within the riparian corridor. A three-expert ensemble voting framework integrated spectral water indices, Dynamic Surface Water Extent rules, and a Random Forest classifier, and the extraction results were validated using 1200 manually interpreted points. Trend analysis, Random Forest attribution, and GeoDetector were then applied to assess temporal changes and the combined effects of climate, topography, and human activity. The extraction achieved an overall accuracy of 96.17% and a Kappa coefficient of 0.923. The mapped open-water area increased from 74.33 km 2 in 2000 to 121.67 km 2 in 2024, corresponding to a net gain of 47.34 km 2 (63.68%). The Mann-Kendall test indicated a significant upward trend ( Z =6.66; P <0.001), with a Theil-Sen slope of 1.45 km 2 /a. Sequential Mann-Kendall analysis identified no robust year of abrupt change, although the increasing trend became significant after 2007. Attribution results showed that topography remained the dominant spatial regulator of water persistence, as low-elevation valley floors concentrate both runoff accumulation and human land use. Population density (PD) and nighttime light (NTL) signals were stronger in urbanized reaches, where high impervious-surface values and mapped water co-occurred around managed water environments, including regulated channels, impoundments, and reservoir storage. Overlay analysis of barriers and reservoirs further suggested that engineering regulation may account for part of the persistent water patches along the corridor. These findings reveal a coupled mechanism involving climate, topography, and human regulation in shaping surface water change in a water-limited plateau river corridor, and provide evidence for water-resource management and ecological restoration in the upper Yellow River Basin.