The Development of a Nonstationary Standardised Streamflow Index Using Climate and Reservoir Indices as Covariates

Under current global change, the driving force of evolution drought has gradually transitioned from a single natural factor to combination and anthropogenic factors. Therefore, widely used standardised indices based on assumption stationarity are challenged may not accurately assess characteristics processes. In this study, nonstationary streamflow index (NSSI) that incorporates climate reservoir as external covariates was developed access hydrological drought. The first step proposed approach is apply methods trend change point analysis nonstationarity series determine type regime, is, altered regime. Then, different models were constructed calculate NSSI by selecting for with covariate Four stations in upper reaches Huaihe River basin, China, selected examine performance NSSI. results indicated Dapoling (DPL), Changtaiguan (CTG), Xixian (XX) had regimes, while Nanwan (NW) station an deviances optimal 17 (2.2%), 18 (2.9%), 26 (4.0%), 22 (3.5%) less than those stationary DPL, CTG, NW, XX stations, respectively. Especially, NW influenced regulations, frequency slight moderate 12.8% lower 13.1% greater SSI, Overall, influence variability regulations provided more reliable assessment traditional SSI.