Development of SWAT-Paddy for simulating lowland paddy fields

Authors: TSUCHIYA, RYOTA - Tokyo University Of Agriculture & Technology; KATO, TASUKU - Tokyo University Of Agriculture & Technology; JEONG, JAEHAK - Texas A&M Agrilife; Arnold, Jeffrey

Submitted to: Sustainability
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2018
Publication Date: 9/11/2018
Citation: Tsuchiya, R., Kato, T., Jeong, J., Arnold, J.G. 2018. Development of SWAT-Paddy for simulating lowland paddy fields. Sustainability. 10:3246-326. https://doi.org/10.3390/su10093246.
DOI: https://doi.org/10.3390/su10093246

Interpretive Summary: Recent increase in the global consumption of rice is causing an increasing need for sustainable water management in rice production. Models are needed by decision makers to evaluate the sustainability of rice paddy cultivation. In this study, the SWAT (Soil and Water Assessment Tool) model was enhanced: 1) to modify the water balance calculation for impounded fields, 2) to add an irrigation management option for paddy fields, which is characterized by flood irrigation with a target water depth, and 3) to add a puddling operation that influences water quality and infiltration rates. The enhanced SWAT model was applied to an agricultural watershed in Japan to test the newly developed rice management routines. The results showed the model could realistically represent rice paddy cultivation, water management, and dischage practices. This improved model will provide decision makers with a tool to develop scenarios for sustainable rice production around the world.

Technical Abstract: Recent increase in global consumption of rice led to increased demand for sustainable water management in paddy cultivation. In this study, we propose an enhanced paddy simulation module in the SWAT model to evaluate sustainability of paddy cultivation. Enhancements added to SWAT are: 1) to modify water balance calculation for impounded fields, 2) to add an irrigation management option for paddy fields, which is characterized by flood irrigation with target water depth, and 3) to add puddling operation that influences water quality and infiltration rate of top soil layer. In a case study, the enhanced model, entitled SWAT-Paddy, was applied to an agricultural watershed in Japan. Results showed that the SWAT-Paddy successfully represents paddy cultivation, water management, and discharge processes. Simulated daily discharge rates with SWAT-PADDY (R2=0.8) were superior to SWAT2012 results (R2=0.002). SWAT-Paddy allows simulating paddy management processes realistically and thus, can enhance model accuracy in paddy-dominant agricultural watersheds.