Determination of SCS Runoff Curve Number and Landuse Characteristics of Khowai River Catchment, Tripura, India

Abstract

Precipitation and runoff can be undoubtedly considered as one of the most significant parameters contributing considerably to the hydrological cycle of a region. Runoff estimation is regarded as the primary aspect in different hydrological considerations. Estimation of the storm water runoff is particularly essential for the effective design of different components in storm water management, and also in the analysis of landuse and landcover pattern changes. The research primarily aims at determining suitable Curve-Number (CN) value for Khowai River basin located in North Tripura, India. The Soil-Conservation-Service-Curve-Number (SCS CN) technique is commonly used for estimating the stormwater runoff of unaged catchment areas. Five land use types (i.e. forest, agricultural land, pasture, wasteland and hard surface) had been reclassified from over 20 land use types and delineated using ERDAS IMAGINE-2010 software. The Hydrologic soil group (HSG) in Khowai catchment area was found to be mainly covered with HSG B. It was also noted that small percentage of areas are covered with HSG C and HSG D type soil. The antecedent-moisture-condition (AMC) II was used in the determination of curve number due to the complex rainfall information. The CN for the Khowai catchment area was extracted and determined from the National-Resources-Conservation-Service (NRCS) curve number tables for runoff. The CN values were then also verified by the precipitation and discharge data of the catchment under study. The subsequent results reveal that CN in the Khowai catchment area varies from 37 to 80, whereby the higher CN-values indicate, the higher runoff potential. It was found that most of the Khowai catchment area was covered by high to very high CN-values and showed an expanding trend in the area. These results provide key information for the next step of runoff estimation and simulation for the Khowai River catchment basin.