Publication Date



Curve Number, Satellite Imagery, Watershed modeling, GIS


An approach to estimate the curve number (CN) at each pixel unit of a satellite imagery, which is a key parameter in the widely used Soil Conservation Service Curve Number (SCS- CN) hydrologic model, is proposed. Instead of mapping land use and its temporal dynamics from satellite imageries, this approach linearly unmixes the multi-spectral radiances into three fractional layers which primarily control the degree of saturation within a watershed occurring due to a 25 cm-depth storm event, i.e., physically interpreted as the CN. The fraction layers used are water, sand and pure vegetation. In order to obtain a relationship between the fractional statistics and CN, a multi-correlationship analysis of known combinations of land use, hydrologic condition and hydrologic soil group is carried out in an agricultural watershed. The obtained relationship is applied onto the fractional layers to compute the spatial distribution of CN. The performance of the SCS-CN model with the spatial CN is found to be 14% more accurate than that of the model results with only land use information from satellite imageries. The spatial difference of two CN layers in which the one represents the condition of the watershed before soil and water conservation measures was taken up and the other for the post conservation period indicates change in the hydrologic response of the watershed spatially.