Evolution and resource utilization assessment of floodwater resources in the Hotan River Basin during the flood season

The influence of global warming, hydrological processes in the arid river basins of Northwest China are becoming increasingly extreme. Clarifying the evolution patterns of extreme hydrological events and advancing flood resource utilization to alleviate regional water scarcity are critical pathways for supporting high-quality regional development. Considering the Hotan River Basin in southern Xinjiang as the study area, we systematically analyzed the spatiotemporal evolution characteristics of flood resources during the flood season from 1962 to 2021. Based on this foundation and considering the current status of water conservancy projects in the basin, we assessed the potential for floodwater resource utilization and projected the impact of water conservancy construction on floodwater resource utilization in the basin. The results indicate the following. (1) Floodwater resources in the basin during the flood season are highly concentrated in July and August, accounting for 72.63% of the total annual flood resources; specifically, the proportion reaches 69.27% and 75.99% at the Wuluwati and Tongguziluoke Stations, respectively. Since 2010, floodwater resources in the basin have generally shown a trend of abundance, with the cumulative anomaly curve of the Tongguziluoke Station exhibiting more drastic fluctuations, reflecting the higher sensitivity of runoff to climate change in the Yulongkashi River than in the Karakash River. (2) Over the past six decades, flood resources during the flood season have increased markedly at a rate of 0.67×108 m3·(10a)-1. The Wuluwati and Tongguziluoke Stations show an increasing trend, with the increment in the latter [0.55×108 m3·(10a)-1] being 4.58 times that in the former. The Hurst index of both stations is 0.72, which is significantly higher than 0.5, indicating a strong persistence in the increasing trend, which provides a stable water volume basis for flood resource utilization. The correlation of flood resources with temperature is significantly stronger than that with precipitation (with an average correlation coefficient of -0.09 and 0.10 for June and July, respectively), indicating greater sensitivity to temperature changes, mainly because glacial and snowmelt runoff accounts for 74.56% of the total runoff in the basin. (3) Between 1999 and 2021, the average available flood resources in high- and normal-water scenarios were 1.36×108 m3 and 1.26×108 m3, respectively. The basin exhibits no potential for flood resource utilization in low-water scenarios. (4) After replacing the plain reservoir with the Yulongkashi Water Conservancy Hub, the flood resource potential can be fully tapped, with an estimated additional 2.74×108 m³ flood resources becoming available. This study provides theoretical support and practical reference for efficient flood resource utilization in arid regions.