Some hydrologic characteristics and modeling aspects Of a small catchment in southern India

Abstract

The area under study is a small catchment called Karanja, having an area of about 2025 km² in Karnataka and adjoining Andhra Pradesh. Observed daily stream flow data and daily rainfall data for the period 1964.1984 and hourly rainfall and river gauge data for the period 1980-84 along with the available data on soil cover, groundwater levels and geology etc, have been utilised. About 80 percent of the catchment area is covered by soils of considerably high runoff potential. About 5 per cent of the catchment rainfall is discharged into the river as base flow from the ground water in a normal monsoon year. Monthly rainfall and runoff were significantly correlated for the months of July to October during the period 1964.1984. Regression equations for estimating runoff have been developed using these relationships. On an average about 33 per cent of the rainfall in the catchment is converted into runoff and the percentage of runoff is maximum in the year 1983 and minimum in 1972. Unit hydrographs corresponding to the seven flood events have been derived and thereby an average unit hydrograph for the catchment is obtained. The validity and application aspects of the derived unit hydrographs are indicated. The unprecedented peak flood of 1983 in the catchment is also briefly discussed.