Keywords: geospatial approach, modified NRCS–CN, rainfall runoff, remote sensing, runoff potential, slope effect, Natural Resources Conservation Service, NRCS curve number, hydrology, watersheds, India
Assessment of the effect of slope on runoff potential of a watershed using NRCS–CN method
The rainfall–runoff is a very complex hydrological phenomenon, as this process is highly non–linear, time–varying and spatially distributed. The average slope within the watershed together with the overall length and retardance of overland flow are considered to be the main factors which govern the runoff process. The Natural Resources Conservation Service curve number (NRCS–CN), formerly known as Soil Conservation Services curve number, is the most widely used method to estimate direct runoff from rainfall, due to its simplicity and the use of the single CN parameter. However, the NRCS–CN method has been developed for limited watershed area and slope. In the present study, the modified NRCS–CN method for slope and CN conversion have been investigated to determine runoff potential of a watershed in geo–spatial environment. Solani watershed, which is a sub–watershed of Ganga basin located partly in Uttarakhand and Uttar Pradesh states of India; has been considered for analysis. The daily rainfall–runoff study has been carried out for year 2006. It was found that slope factor effects runoff estimation significantly.