Analysis of drought characteristics over Luanhe River basin using the joint deficit index

In order to describe the overall drought status objectively, a copula-based joint deficit index (JDI) was adopted for analyses of drought characteristics in Luanhe River basin. Monthly precipitation data from 1958 to 2011 selected from 26 rain-gauge stations were used for calculating the JDI. The JDI, which encompasses multiple deficit statuses over time scales from 1 to 12 months by using the 12-dimensional empirical copula, is shown to be capable of providing a comprehensive and objective assessment of droughts. In addition, it is demonstrated that both emerging and prolonged droughts can be captured by the JDI. Results of the drought evaluation over the Luanhe River basin indicate that the frequency of drought occurrence generally increases from northwest to southeast, and droughts observed in summer and autumn are more frequent and severe. Compared with the northwestern part of the area, the drought events in the southeast are characterized by longer duration and greater severity. Furthermore, a general tendency of drying is found in the flood season (July to September) over the basin, with significant aggravating trends in the southeastern part. These related drought characteristics could provide valuable information and references for regional mitigation strategies and water resource management.