GIS-Based Hydrological Modelling Using Swat: Case Study of Upstream Watershed of Jebba Reservoir in Nigeria

Abstract

Hydrological modeling tools have been increasingly used worldwide in the management of water resources at watershed level. The application of these tools have been improved in recent time through the advent of remote sensing and Geographical Information System (GIS) techniques which enhance the use of spatially and physically based models to simulate and predict some of the major functions of watershed systems. In this study, the focus was on the applicability and feasibility of SWAT model interfaced with GIS software (MapWindow) in the prediction of stream flow of a watershed located upstream of Jebba reservoir in Nigeria. The flow predictions by SWAT were calibrated (from Jan. 1990 to Dec. 1992) and validated (from Jan.1993 to Dec.1995) against measured flow data while the performance evaluation of the model was achieved using coefficient of determination R² and Nasch-Sutcliffe Efficiency (NSE). Sensitivity analysis of the model parameters showed that curve number is the most sensitive parameter for estimation of stream flow within the catchment. The model results showed a good correlation with the observed data with values of 0.76 for R² and 0.72 for NSE   during calibration period. For validation periods, R² and NSE values were 0.71 and 0.78 respectively. This interesting results of SWAT  is an indication that a properly calibrated SWAT can be an ideal modeling tool for supporting water resources management policies and decisions at watershed level in the region and other river catchments in Nigeria