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

Simulation of rainfall-runoff process for ungauged catchments is an important area of research in surface water hydrology. A number of well established techniques are currently available for this purpose. The derivation of unit hydrograph has been extensively investigated by many researchers ever 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.

As the historical hourly rainfall-runoff data was available for Barchi nala catchment, the Geomorphological Instantaneous Unit Hydrograph (GIUH) based Clark model methodology was applied to compute and compare the surface runoff hydrographs for a few selected rainfall-runoff events. Because hourly rainfall-runoff records were not available for Malaprabha catchment, the methodology was applied for hypothetical events with different equilibrium velocities.

The geomorphological parameters and time-area diagram form important inputs for the GIUH based Clark model and these parameters for each catchment were generated using the Geographic Information Systems (GIS) package Integrated Land and Water Information Systems (ILWIS). The observed and computed direct surface runoff hydrographs show a reasonable association.

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