CS(AR)-31/98-99 : Rainfall runoff modelling of Western Ghat region of Karnataka

Abstract

The water yield is an integration of discharge as a function of time for a specified duration and reflects the volumetric relationship between rainfall and runoff. The estimation of water yield is required for solution of water resources problems normally encountered in design of storage facilities, water availability for agriculture, industrial or drinking purpose, dependable water supply for power generation, planning irrigation operation and design of irrigation projects. Keeping in this view, the effort has been made to develop a regional conceptual catchment water balance model parameters which can he used to estimate the water yield from ungauged catchments located in the same region. In the present study, five catchments in the western ghat region have been selected. Out of which. three river basins are westward flowing and two rivers are eastward flowing in nature.

The regionalised parameters of the catchment water balance model have been obtained by developing relationship between model parameters such as wetting potential, vaporisation potential, initial abstraction coefficient of base flow and surface flow with mean annual rainfall, and vegetation cover of the basin. However, coefficient of determination between vegetation cover and the model parameters found to be very high and where as the relationship between mean annual rainfall and model parameters is very low. The regional parameters obtained are compared with calibrated parameters and found to be within the tolerable limits. Water balance components are simulated using both regionalised and calibrated parameters of the model. The variation between the simulated values are within 10 per cent. Therefore it is suggested that model parameters can be obtained from the established relationship between vegetation cover of the basin and the model parameters.