Study on hydrological drought evolution characteristics in Ankang Reach of upper Hanjiang River from 1991 to 2022

In order to ensure the water resource security of the upper Hanjiang River, Standardized Runoff Index(SRI) was used to calculate the runoff from 1991 to 2022 of Ankang Reservoir, the main control project of the upper Hanjiang River.Then combined with risk indicators (reliability, elasticity and vulnerability), the hydrological drought evolution characteristics assessment index (SRI-RRV) was constructed to evaluate the hydrological drought evolution characteristics of Ankang Reach of upper Hanjiang River.The results show that: ① The annual runoff of Ankang Reservoir fluctuated greatly from year to year during 1991 to 2022, but showed a relatively obvious increasing trend in general.② There was no special drought in the study area, except one severe drought occurred.The hydrological drought was mainly light and moderate drought, of which 95 were light drought, indicating that there was a certain risk of hydrological drought in the study area.③ At the seasonal scale, the decreasing order of the degree of drought tendency in the study area was winter > spring > autumn > summer.④ In the hydrological drought risk assessment of the study area, the reliability and resilience from 2007 to 2022 were generally increased compared with that before 2006, and the vulnerability was reduced compared with that before 2006, indicating that the hydrological drought risk of Ankang section in the Hanjiang River had decreased as a whole in recent years.⑤ From 1991 to 2022, the comprehensive evaluation results of hydrological drought in the study area were mainly poor (19 times), and the evaluation grade was good only once, indicating that the risk of hydrological drought in the study area still cannot be ignored, and it is necessary to further strengthen the protection and management of water resources to cope with the adverse effects of hydrological drought.