7-Assessment of Low Flow and Stream Flow Drought Severity in Ken Basin

Abstract

Low flow appraisal of rivers in time and space has vital importance in the formulation of round the year plan of water uses comprising domestic and industrial water supply, irrigation scheduling, reservoir operation, in-stream flow maintenance etc. Stream flow drought severity analysis including the estimation of low flow, drought duration, time of occurrence and deficit volume etc. was carried out using 22-42 years (1960-2001) 10-daily stream flow data of the Ken river system. A variable truncation level approach has been applied for identification of drought events. Independent stream flow drought events have been derived using a pooling procedure for mutually dependent drought events. The severity of an independent drought event is classified using a new drought severity index (DST,) defined as a function of (i) the ratio of deficit flow volume to corresponding volume at the truncation level and (ii) the ratio of duration of deficit flow to the maximum possible duration of the independent stream flow drought event. The study found that the stream flow droughts in Ken basin up to the Madla site are more prolonged and relatively severe than those in the lower reach of river course at Banda. The drought events starting during August-October were found to be more prolonged and be severe drought events than those starting in other months.