Estimation of streamflow of the ungauged mountainous watersheds of the Western Ghats in India using the SWAT model

Abstract

AbstractThe Western Ghats in the humid tropical zone of Kerala State, India have several drinking water, irrigation and hydroelectric projects, which exclusively depend on streamflow. The seasonal monsoon rainfall imposes several limitations in estimating the streamflows. The rugged topography of these highland areas with thick forest vegetation restricts the installation of conventional gauging stations. Considering these factors, an attempt is made to estimate the streamflow from these watersheds using the Soil and Water Assessment Tool model. Eight representative watersheds with stream gauging stations were selected, of which six were used for initial calibration, validation of the model and identifying the model parameters to be regionalised. The regionalised model was then applied to the other two watersheds, and the estimated data were compared with the observed. Global average, regression method and common parameter transfer approaches were adopted to regionalise the parameters. The calibrated model parameters are averaged in the global average method. The regression function in the data analysis add‐on in the Excel platform determined the functional relationship between the watershed characteristics and the model calibration parameters. The parameter transfer helped recognise two standard sensitive parameters. It is found that by providing the topography, land use and soil data, the streamflow from the ungauged watersheds of the highland belt in the wet humid tropical zone of Kerala can be satisfactorily simulated.