A study on geomorphological response for estimation of direct runoff in kothuwatari watershed

Hydrological data of Kothuwatari sub-watershed comprising an area of 2793 hectares of the Tilaiya dam catchment of Upper Damodor valley, located in Hazaribagh district of Jharkhand State (India) were analyzed to study the geomorphological response for estimation of direct runoff by using Geomorphological Instantaneous Unit Hydrogroph (GIUH) model. GIUH model was based on storm basis incorporating geomorphological parameters with the hydrological characteristics of the watershed. Geomorphological parameters such as bifurcation ratio (RB), length ratio (RL) and area ratio (RA), were derived graphically from topographic maps of the watershed satisfying Horton’s (1945) law when ordered according to Strahler (1957) ordering procedure. A synthesis of the hydrologic response of Kothuwatari watershed to surface runoff was derived by linking the instantaneous unit hydrograph. (IUH) to the geomorphological permeters, watershed to surface runoff was derived by linking the instantaneous unit hydrograph. The GIUH of the watershed was calibrated using the observed direct runoff hydrograph data. Direct runoff hydrographs were obtained from GIUH and these were compared with the observed DRHs to judge the performance of the model. The model performed well for all the test data sets with high coefficient of efficiency, lower relative squared error and absolute relative error in computed peak flow rates values and near zero Coefficient of Residual Mass values. The percentage absolute error in time to peak between computed and observed direct runoff hydrograph was found to be zero percent. The performance of the model showed that it simulates components of direct runoff of hydrographs well.