Examination of the water balance of irrigated paddy fields in SWAT 2009 using the curve number procedure and the pothole module

AbstractThe Soil and Water Assessment Tool (SWAT), a basin-scale hydrological and water quality simulation model, has become popular in Asia for assessing the impacts of land use and human activities including paddy rice (Oryza sativa L.) cultivation which is a typical agricultural management system in Asia. The water ponding and drainage management in paddy fields should significantly affect the regional hydrology and water quality; however, the suitability of SWAT for simulating paddy hydrology at a field scale has not been thoroughly examined.In this study, the water balance of irrigated paddy fields in SWAT was examined for a small watershed where actual daily irrigation data were available. Two approaches available in SWAT to calculate hydrology in a watershed containing paddy fields, the curve number procedure and the pothole module, were applied with the regional paddy rice management standard.The water balance components estimated using the pothole module were significantly different from the actu...