Drought Severity Analysis Using Ephemeral Streamflow Data

摘要

Drought duration and seventy (= deficit volume) of the past events occurred in the Sonar and Bearma sub-basins are analyzed, and the availability of flow in these ephemeral streams during normal and lean years estimated. Such a drought analysis for ephemeral streams does not appear to have been reported in literature. The probabilities of occurrence of zero and non-zero flows and joint probabilities of non-zero flows are estimated to derive flow duration curves to derive monthly truncation levels (at 75 percentile) for describing wet and drought periods. To this end, 15 years and 24 years monthly data of Sonar and Bearma rivers, respectively, were used. The study reveals that the hydrological droughts in these basins (a) usually begin during August-October and (b) either terminate during the period between September and December or may continue till the onset of the next monsoon. Drought events starting during early monsoon months are found to be more severe than those starting during the late or post monsoon months, and the variable truncation approach is efficacious in depicting both the drought and wet events and, therefore, in describing the drought duration and severity.