ESTIMATION OF DISCHARGE FOR UNGAUGED CATCHMENTS USING RAINFALL-RUNOFF MODEL IN DIDESSA SUB-BASIN: THE CASE OF BLUE NILE RIVER BASIN, ETHIOPIA.

Runoff estimation in ungauged catchments is probably one of the most basic and oldest tasks of hydrologists. This long-standing issue has received increased attention recently due to the prediction in ungauged basin initiative by the International Associations of Hydrological Science. In developing countries like Ethiopia most of the Rivers are ungauged. Therefore, applying regionalization techniques for ungauged or poorly gauged river basin is crucial. This paper deals with predicting discharge at ungauged catchments using conceptual lumped rainfall-runoff model HBV-96 in Didessa sub-basin. Four regionalization methodswere applied to transfer model parameter values from the gauged to the ungauged catchments. In regional model, gauged catchments model parameters and physical catchment characteristics of ungauged catchments were used to develop the equations. Sensitivity analyses of eight model parameters wereperformed manually by trial and error