Mathematical Development Model for Estimating Direct Runoff for Kothuwatari Watershed

Abstract

Water resources planning, development and operation of various schemes requires accurate estimation of hydrologic response of the basin. Quantification of direct runoff is an essential input for planning and design. Direct runoff Hydrological investigations were carried out to develop mathematical model for estimation of direct runoff for Kothuwatari watershed of an area of 27.93 km² on storm basis. 15 single peaked isolated storm events were considered for determination of geo-morphological parameters of the watershed. The computed direct-runoff hydrographs ordinates by developed model were compared with the observed direct runoff hydrographs of the corresponding storm events. Coefficient of efficiency and percentage absolute deviation in time to peak were employed for quantitative comparisons. Average values of the shape factor, n and catchment storage coefficient, K, were determined to be 2.446 and 0.695 hour, respectively. The model resulted in closer agreement of rising segment and crest segment to the observed storm runoff hydrographs of the corresponding storm events. The peak runoff rates and recession segment of storm runoff hydrographs computed by the model was found to be in better agreement with the observed peak runoff rates. Percentage absolute deviation in peak flow rate between computed and observed storm runoff hydrographs of the model varies from 17.60-50.92 and the coefficient of efficiency between computed and observed storm runoff hydrograph of its model varies from 0.690 – 0.960. The overall qualitative and quantitative performance of the model for computed of direct runoff hydrograph was adjudged to be better and used for prediction of storm runoff for watershed with sufficient degree of accuracy with acceptable limits.