Application of scs-cn method for estimation of runoff in a humid microwatershed

Tiewri Lyngdoh Nonglait and B K Tiwari

When precipitation rate is greater than infiltration capacity, it results in surface runoff. The aim of this study was to estimate the runoff depth in a microwatershed using Soil Conservation Service Curve Number method. The method incorporates several watershed runoff producing characteristics, viz., soil type, land cover and practice, hydrologic condition, and antecedent moisture condition. The Soil Conservation Service Curve Number values were obtained for various land use elements under different surface conditions associated with a particular antecedent moisture condition. The hydrologic soil groups were assigned after infiltration rates were obtained. For estimation of runoff, eighteen storm events were selected based on the continuity and uniformity of the rainfall over the microwatershed. The runoff estimated using Soil Conservation Service Curve Number method was highest in disturbed forest and lowest in the vegetable fields. The runoff generated in each landuse element using Soil Conservation Service Curve Number method was compared with the observed runoff generated using Web-based Hydrograph Analysis Tool software. The results showed that there was no significant difference between observed and estimated runoff depths.

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