Evaluation of curve number and geomorphology-based models for surface runoff prediction from ungauged watersheds

摘要

Prediction of surface runoff from ungauged and inadequately gauged watersheds in India necessitates development of models to simulate the watershed hy-drologic responses. To accomplish this, curve number (CN) approaches and geomorphological instantaneous unit hydrograph (GIUH) models are used. This article discusses the adequacy of a modified exponentially distributed GIUH (ED-GIUH) model in generating direct runoff hydrographs (DRHs). The ED-GIUH concepts were used to generate the DRHs for the Banha watersheds under the Upper Damoder Valley, Jhark-hand, India. The estimated runoff using the ED-GIUH concept was compared with the original natural resources conservation service curve number (NRCS-CN) generated runoff and validated with the observed runoff data of the watershed. The model input data, including natural drainage network and Horton's morphological parameters were estimated using a watershed morphological estimation tool interface of Ar-cGIS registered . The path probability of channel and overland flow was estimated from the generated feature classes of watershed topology and drainage networks to derive the instantaneous unit hydrograph (IUH). Further, from the IUH, an accounting procedure was used to estimate the unit hydrograph and DRHs for different rainfall events occurring over the watershed. It was observed that the ED-GIUH technique was better (coefficient of determination R super(2) = 0.97, model efficiency E = 0.96) than the NRCS-CN approach (R super(2) = 0.74, E = 0.71) with respect to the observed DRH resulting from rainfall events of 6 h duration or less. However, for rainfall events greater than 6 h, the ED-GIUH method (R super(2) = 0.71, E = 0.58) failed to predict the surface runoff accurately compared to the CN method (R super(2) = 0.89, E = 0.84). Thus the ED-GIUH model could be used to predict DRHs from small-duration events more accurately than the CN approaches for ungauged watersheds having similar geomorphological characteristics as that of the Banha watershed.