CS(AR)-21/99-2000 : Derivation of GIUH for small catchments in hard rock region

Abstract

Simulation of rainfall-runoff process for ungauged catchments is one of the most important areas of research in surface water hydrology. A number of well established techniques are currently available for this purpose. Derivation of unit hydrograph has been extensively investigated by many researchers since Sherman introduced the principle of unit hydrograph. These methodologies require historical rainfall-runoff records for a specific period. Therefore, use of geomorphological characteristics of a basin for deriving hydrograph parameters, as proposed by Rodriguez-Iturbe and Valdes, is advantageous for ungauged catchments.

In the present study, the methodology developed at NIH to relate Clark model parameters to geomorphological characteristics has been used to develop unit hydrograph for two hard rock catchments, Barchi nala and Malaprabha upto Khanapur. This model has already been successfully implemented for simulation of flood events in small catchments of Kolar sub-basin of Narmada river and Upper Narmada and Tapi sub-zone.

Since the historical hourly rainfall-runoff data were available for Barchi nala catchment, the GIUH based Clark model methodology was applied to compute and compare the surface runoff hydrographs for few selected rainfall-runoff events. Since hourly rainfall-runoff records were not available for Malaprabha catchment, this methodology was applied for hypothetical events with different equilibrium velocities. The geomorphological parameters and time-area diagram form important input for the GIUH based Clark model and these parameters for each catchment were generated using Geographic Information System (GIS) package ILWIS (Integrated Land and Water Information System). The observed and computed direct surface runoff hydrographs show a reasonable comparison.