Reducing uncertainties in infiltration model using SCS-CN for mixed land use catchment

Abstract

Soil Conservation Services (SCS) is a quite popular method to estimate the infiltration of the catchment. The method has an advantage since it can be used for various land use and soil type using a single parameter of Curve Number (CN). However, the method may not suit catchment scaled due to land use heterogeneity. Averaging the CN value for the catchment of mixed land use may produce different runoff estimations compared to individual land-use calculations within the catchment. This situation will lead to higher uncertainty in the estimation of CN. This study investigates the effect of sub-catchment delineation to improve the CN estimation on catchment scaled. It shows that when the catchment is divided into smaller sub-catchment based on second level tributaries, the dominant land use of more than 80% in the basin increases to 50% of the whole catchment. This indicates that runoff computation shall improve by using the weighted CN as proposed in this study.