Estimating Floods from an Ungauged River Basin Using GIUH-Based Nash Model

Among the existing mesoscale rainfall-runoff models, the geomorphological instantaneous unit hydrograph (GIUH) models can predict the streamflow reasonably well in less data availability conditions using the measurable basin geomorphology. In light of this, the rainfall-runoff transformation process of the Baitarani River Basin at Anandapur in eastern India was studied herein using the GIUH-based Nash model. In this model, the gamma function of the Nash model is approximated that does not need the computation of either the complete or incomplete gamma functions. To evaluate the efficacy of this model, four performance evaluation measures of Nash–Sutcliffe efficiency, percentage error in volume, percentage error in peak, and percentage error in time to peak are used. The results reveal that the GIUH-based Nash model performs with the average Nash–Sutcliffe model efficiency of 87.21(±8.05) % with overprediction of the runoff volume by 29.91(±18.76) %. However, this model could estimate the runoff peak more accurately with an average peak error of 3.86 (±2.50) % having an average time to peak error of 2.08(±4.17) %. Hence, overall, the GIUH-based Nash model has the capability of estimating the basin-scale runoff reasonably well.