CS(AR)-5/2000-2001 : Applicability of SCS Runoff method to different Agroclimatic regions

Abstract

The most generally available data in India are the rainfall amounts measured by non-recording rain gauges and for such data, USDA, Soil Conservation Service (SCS) Curve Number method is a well accepted tool in Hydrology for the estimation of design floods for small hydraulic structures and for other rainfall-runoff analyses. This is a simple, predictable, and stable conceptual method. The Curve Number (CN) is a measure of water retention in the watershed. The SCS method assumes the initial rainfall abstraction as the fraction of potential maximum retention of the soil. The initial abstraction coefficient was developed for small experimental watersheds in USA. The same coefficient may not hold good for Indian conditions. Therefore, in the present study, it is proposed to establish the initial abstraction parameter in the SCS method and to assess the influence of various hydrological parameters in generating direct runoff from the watersheds in hard rock region under different physiographic and climatic conditions.

Observed rainfall-runoff event data has been used to estimate the average curve number for six small hard rock catchments, namely, Dandavati, Varada, Honnammanahalla, Barchinala, Yettinahole and Jadkalhole. Natural and frequency matched data sets were used for the analysis. The calculated curve number values have been further used to estimate the initial abstraction coefficient for the study watershed.