The SRI (system of rice intensification) water management evaluation by SWAPP (SWAT–APEX Program) modeling in an agricultural watershed of South Korea

In this study, a potential system for achieving rice intensification (SRI) water management in an agricultural watershed of South Korea was evaluated using the SWAT–APEX Program, SWAPP. The SWAPP was calibrated and verified at the level of the paddy field for a 373.6 km2 watershed using 6 years (2000–2005) of streamflow, and total nitrogen (T-N) and total phosphorus (T-P) stream water quality data. The five ponding depth management of 20, 40, 60, and 80 mm was tested for the entire growing period and the irrigation water saved using this approach was 68.6, 28.0, and 17.3 % when compared to the actual depth management. The T-N load was reduced by 10.1, 4.2, and 2.9 % and the T-P load was reduced by 12.9, 6.0, and 4.5 %, respectively. These results showed that water could be saved and the nutrient load reduced by just applying SRI water management for rice paddies in South Korea.