Estimation of Runoff Using Curve Number Method And Its Modifications

Abstract

Watershed is the range covering all the land that contributes spillover water to a typical point. Propels in computational power and developing accessibility of spatial information have made it conceivable to precisely foresee the overflow. The likelihood of quickly consolidating information of various sorts in a Geographical Information System (GIS) has prompted noteworthy increment in its utilization in hydrological applications. Numerous strategies are utilized to appraise the overflow from a watershed. The bend number technique, otherwise called the hydrological soil cover complex strategy, is an adaptable and broadly utilized system for overflow estimation. This strategy incorporates a few imperative properties of the watershed to be specific, soils penetrability, arrive utilize and predecessor soil water conditions which are mulled over. In the present review, SCS strategy and its adjustments is utilized with GIS to gauge the overflow. The review territory is the Neyyar watershed. The watershed has a geological territory of 490km2. The precipitation and land utilize information were utilized alongside the test information of soil order for the estimation of the spillover for the review zone.The predicted runoff values obtained by the three methods were compared with the observed values and the results were validated.It was found that using all the rainfall data, the modified CN I performed the best (E = 0.95, R² =0.97), followed by the NRCS-CN method (E = 0.89, R² =0.95) and CN II method (E = 0.83, R² =0.85).