Generalization of Relationship Between Antecedent Moisture and Antecedent Rainfall for SCS-CN-based Rainfall-Runoff Model

One ofthe popular methods to estimate the depth of surface runofffor a given rainfall is the Soil Conservation Service Curve Number (SCS-CN) method. in this method, variation of antecedent moisture condition (AMC) is not continuous. Though the Mishra-Singh model⁽⁵⁾ avoids this problem, its expression for computation of antecedent moisture (M) is based on the assumptions, which are away from reality. Recently, Sahu et al.⁽⁶⁾ suggested better continuous relationship between M and the antecedent 5-day rainfall (P₅). But the drawback of this relationship is that it completely ignores the effect of potential maximum retention (S) on M. in reality, higher is the S, higher will be the M, for a given amount of P₅. The present study generalizes the relationship between M and P₅. Coupling this new relation with the basic equations of the Mishra-Singh model, a new model is proposed and comparedfor performance with SCS-CN method, Mishra-Singh model, and Sahu et al.⁽⁶⁾ model, by applying them to a large number of small watersheds of USA. The proposed new model has been found to perform equally well to Sahu et al. model, and better than Mishra-Singh and SCS-CN models. Since the proposed model is hydrologically better than the others, the former can be preferred to the latter.