Altered drought propagation under the influence of reservoir regulation

Abstract

Human interventions (HI) are significantly affecting the land surface hydrological cycle, and thus altering the occurrence of hydrological drought. So far, however, how HI affect the propagation from meteorological to hydrological drought is still unclear. In this study, we proposed a quantitative diagnosis framework and assessed the impacts of HI on drought propagation across varying scales over the typical reservoir-dominant Daling River basin (DRB) in China, in which the Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSI) were utilized to identify the meteorological drought (MD) and hydrological drought (HD), respectively. Our results show that the in-situ streamflow records were found with an evident turning point around 2003, coincident with the operation of the largest reservoir in DRB. Under the influence of reservoir operation, the HD frequency saw an obvious intensification and the correlations between MD and HD exhibited a decreasing tendency, especially during the wet season. The seasonality of drought propagation changed significantly for both up-downstream and MD-HD, as indicated by the advance of drought events from autumn to summer and the aggravation of autumn drought. The reservoir operation changed the HD events characteristics by increasing the drought duration and severity. Our results highlight the strong aggravating effect of reservoirs on drought propagation.