III-8-Runoff Estimation from a Small Watershed using GIUH Approach in a GIS Environment.

Abstract

A geomorphological instantaneous unit hydrograph (GIUH) is derived from the geomorphological characteristics of Kothuwatari (29.67 km2) watershed, a sub-watershed of upper Damodar Valley, Hazaribagh, Jharkhand, India and it is related to the parameters of the Clark instantaneous unit hydrograph (IUH) model for deriving its complete shape. The model parameters of the Clark model were determined by Newton-Rapson non-linear optimization technique, using the Geomorphological characteristics of the watershed. Various geomorphologic characteristics of the study watershed have been determined from the toposheets 7211/7 and 7211/8 by using the GIS software, Integrated Land and Water Information System ILWIS 3.0. The developed GIUH based Clark model has been applied for simulation of the direct surface run-off (DSRO) hydrographs for nine rainfall-runoff events of the Kothuwatari watershed. The performance of the model has been evaluated by employing performance indices viz., coefficient of efficiency, absolute average error, root mean square error, average error in volume and absolute percentage deviation in peak flow rates. The results indicates that the coefficient of efficiency varies from 63.13 to 97.78, absolute average error varies from 0.32 to 2.56 m3/s, root mean square error varies from 0.54 to 4.724 m3/s, average error in volume varies from -0.037 to 0.005 m3 and absolute percentage deviation in peak flow rates varies from 0.422 to 8.80.The DSRO hydrographs are computed with reasonable accuracy by the GIUH based Clark model, which simulate the DSRO hydrographs of the catchment considering the Kothuwatari watershed to be ungauged.