Bivariate socioeconomic drought assessment based on a hybrid framework and impact of human activities

Abstract

Socioeconomic drought generally occurs when water supply cannot satisfy water demand. This study proposed a hybrid framework for socioeconomic drought assessment, involving the construction of standardized water supply-demand reliability index (SWSDRI), truncation of drought events, and classification of bivariate drought levels. Using the run theory, socioeconomic drought events and their properties, including duration and severity, were characterized by the SWSDRI series. Then, bivariate socioeconomic drought levels, based on the Kendall frequency of drought duration and severity, were classified using the copula function. Impacts of human activities on socioeconomic drought, including mainly the regulation of reservoirs and water consumption were quantified in the Dongjiang River basin, located in the south of China. Results showed that the framework, based on SWSDRI, facilitated the investigation of socioeconomic drought properties. The joint distributions of drought duration and severity, based on naturalized streamflow and under the individual and total impacts of human activities, were fitted well by the Archimedean copulas. Both drought duration and severity clearly exhibited the slight, moderate, severe, and extreme droughts classified by bivariate drought levels. For naturalized streamflow, socioeconomic drought occurred approximately once a year in the Dongjiang River basin. Design values of the combination of drought duration and severity accounted for 3.4 months and 8.0 hundred million cubic meters of the boundary between slight and moderate droughts, 4.9 months and 13.6 hundred million cubic meters of the boundary between moderate and severe droughts, and 6.9 months and 20.0 hundred million cubic meters of the boundary between moderate and severe droughts, respectively. Under the impact of human activities, in particular the regulation of reservoirs, socioeconomic drought was remarkably alleviated with a decrease of 45.8% in quantity. If the impact of water consumption was considered, drought events in quantitive terms remained almost unchanged, but more extreme and severe droughts occurred, because some slight, moderate, and severe droughts were aggravated by one level. Among the main reservoirs, the impact of the Xinfengjiang reservoir in the period of its operation was remarkable with a decrease in drought events by 47.7%. Under the impact of the Fengshuba reservoirs, drought events changed little in quantitive terms, but more slight droughts occurred because some moderate, severe, and extreme droughts were alleviated.