The Soil Conservation Service Curve Number (SCS-CN) method is one of the most popular and accepted method for runoff estimation at watershed scale.The attractive feature of the SCS-CN method is that it integrates the complexity of runoff generation into single parameter, i. e. CN. In last decade, the method has received much attention in the hydrologic and watershed management literatures. Recent contributions have significantly enhanced its application potential. This book covers proposed methodology containing three approaches to determine CN viz. modifying CN by using cumulative rainfall-runoff ordered data, by integrating morphometric parameters, and by incorporating evapotranspiration. This book will be of special appeal to hydrologic research scholars, modelers and model users. I shall feel amply rewarded if the book proves helpful in the field applications in semi-arid hydro-meteorological regions as well as in the development of genuine research studies.