Author(s): R. K. Sahu; S. K. Mishra; T. I. Eldho; M. K. Jain
Linked Author(s): Eldho T.I.
Keywords: Ntecedent rainfall; Antecedent moisture; Curve number
Abstract: Modeling of an event-based rainfall-runoff process is important in Hydrology. Soil Conservation Service Curve Number (SCS-CN) method is one of the widely used methods for computation of runoff from the given rainfall amount. Despite the fact that a number of modifications have already been suggested, there still exists a need for further improvement in the method for more accurate results. Literatures indicate that there is no clear definition of antecedent moisture which, of course, depends on antecedent rainfall. This study presents a SCS-CN-based modified model which allows direct use of ‘antecedent rainfall’ in the runoff equation and thus removes the ambiguous term ‘antecedent moisture’ and then evaluates its impact. In an application to a large set of data from 84 small watersheds, varying in area from 0. 17 to 71. 99 ha, of U. S. A., the proposed modified model for varying λ has been found to perform better than any of the investigated seven versions of the SCS-CN-based models. This performance is based on two statistical criteria viz. root mean square error (RMSE) and normalized root mean square error (nRMSE). This model yielded the lowest values of mean RMSE and mean nRMSE. It advantageously obviates sudden jumps in the curve number with antecedent moisture condition which is an undesirable feature of the existing SCS-CN model.
Year: 2005