Insights for river water resource management on the Qinghai–Tibet Plateau: Perspectives from stable isotopes and the ecological environment

Abstract

Directly quantifying river evaporation loss and internal water vapor circulation on the Qinghai–Tibet Plateau (QTP) poses significant challenges. However, stable isotope technology has emerged as an effective method for revealing the internal dynamics of river water. This study was the first to estimate the evaporation loss and recirculating precipitation of rivers in summer on the QTP based on the stable isotope technology. Combined with remote sensing technology, the ecological and hydrological effects of river internal circulation on vegetation growth were revealed. Our findings revealed that the average river evaporation loss ratio was 14.86 % ± 1.2 %, whereas the average river recycled precipitation ratio was 12 % ± 0.36 % in summer on the QTP. Notably, the cumulative recycled precipitation of rivers in summer reached 702.5 × 10⁸ m³, which was comparable to the water capacity of Qinghai Lake. Vegetation around the river on the QTP has demonstrated a nuanced nonlinear response to both river evaporation loss and recycled precipitation. Specifically, the normalized difference vegetation index (NDVI) value of 0.4 and the recycled precipitation of 10 mm emerged as critical thresholds, marking significant inflection points for vegetation growth promotion around the river. Notably, the regions with the highest river evaporation loss were concentrated in river source regions in summer, underscoring the necessity of implementing ecological stewardship in these critical zones. In light of these observations, it is imperative to consider the far-reaching ecological consequences of river evaporation loss and recycled precipitation, particularly within the river source regions on the QTP. The research and vigilant monitoring are essential to facilitate sustainable river water resource management and mitigate potential ecological disruptions in this ecologically sensitive region.