Performance Evaluation of SWAT-based Model for the Prediction of Potential and Actual Evapotranspiration

Abstract

Hydrological models have become an important tool for the efficient management of water resources. However, selection of appropriate models for evapotranspiration (ET) computations in river basins remains challenging to watershed managers, especially in data-scarce regions. The performance of Soil and Water Assessment Tool (SWAT) based model for the prediction of potential and actual evapotranspiration (PET and AET) of Ogun-Oshun River basin, Nigeria was investigated. Spatial and meteorological data were applied in setting up Map-window SWAT model. The three existing methods: Penman-Monteith, Priestly-Taylor (radiation-based) and Hargreaves (temperature-based), available in SWAT were applied for the evaluation of PET and AET using soil, topographic, land-use and meteorological data as input parameters. The model results show a good agreement between the observed and simulated dataset as shown by Nasch-Sucliffe Efficiency and coefficient of determination values. For the 30 years simulation period, the predicted average PET for Penman-Monteith, Priestley-Taylor and Hargreaves methods were 1791.516, 1684.597, and 1724.563 mm with corresponding standard deviation values of 89.322, 53.824 and 77.867 mm, respectively. The analysis indicated that Penman-Monteith and Hargreaves methods yielded almost the same results while Priestly-Taylors method slightly differs which establish that it is not very suitable for arid/semiarid regions. The study could be beneficial to watershed managers in addressing climate-related problems and for sustainable water resources management.