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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #312858
Title: Development and validation of a basin scale model PCPF-1@SWAT for simulating fate and transport of rice pesticides

Author
item BOULANGE, JULIEN - Tokyo University Of Agriculture & Technology
item WATANABE, HIROZUMI - National Institute For Agro-Environmental Sciences
item INAO, KEIYA - National Institute For Agro-Environmental Sciences
item IWAFUNE, TAKASHI - Food Research Institute - Japan
item ZHANG, MINGHUA - University Of California
item LUO, YUZHOU - University Of California
item Arnold, Jeffrey

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2014
Publication Date: 5/15/2014
Publication URL: http://handle.nal.usda.gov/10113/60418
Citation: Boulange, J., Watanabe, H., Inao, K., Iwafune, T., Zhang, M., Luo, Y., Arnold, J.G. 2014. Development and validation of a basin scale model PCPF-1@SWAT for simulating fate and transport of rice pesticides. Journal of Hydrology. 517:146-156.

Interpretive Summary: Rice is a staple of diets in many countries around the world. However, the use of pesticides in rice production creates a potential environmental hazard of the pesticides that leave the rice paddys and enter rivers and lakes. In this study, the watershed model SWAT (Soil and Water Assessment Tool) was linked to a model for simulating pesticide fate and transport in rice paddys (PCPF-1). The combined model was tested for its ability to simulate water flow and pesticide outflow from rice paddys in the Sakura River in Japan. The model was shown to accurately predict pesticide concentrations in the river, thus making it a potentially useful tool for developing management strategies to minimize the pesticide transport.

Technical Abstract: The objective of this study was to develop, verify, and validate a new GIS-based model for simulating the fate and transport of rice pesticides in river basins. A plot scale model simulating pesticide fate and transport in rice paddies (PCPF-1) was incorporated into the Soil and Water Assessment Tool (SWAT) basin scale water and pollutant transport model. The new combined model, PCPF-1@SWAT model, was first used on some base-case scenarios to verify that the PCPF-1 algorithm and the routing of variables were correctly implemented. Next, the PCPF-1@SWAT model was calibrated and validated on the Sakura River basin (Ibaraki prefecture, Japan) using mefenacet concentrations measured during the rice growing season in 2008. The modeling procedures for simulating pesticide fate and transport in a Japanese river basin were demonstrated by providing model parameters related to hydrology, land use, pesticide fate, and rice field managements methods. The water flows predicted by the PCPF-1@SWAT model in the Sakura River basin were accurate throughout the whole simulation year, with R2 and ENS statistics exceeding 0.74 and 0.71, respectively for daily flow. The use of different seepage rates had appreciable influence on the simulations. High seepage rates gave a slight overestimation of the predicted base flow during the rice growing period, whereas the base flow predictions using lower seepage rates were comparable to measured data. The PCPF-1@SWAT model successfully simulated the fate and transport of mefenacet in the Sakura River in which measured mefenacet concentrations peaked soon after the initial herbicide application in May, and decreased gradually during the months of June and July. Occasional major precipitation events caused the mefenacet concentration in streams to peak quickly due to a corresponding loss of mefenacet from paddy areas, and then rapidly decrease due to dilution by excess rainfall discharge. The simulation using a seepage rate of 0.12 cm day-1 had the most accurate prediction of mefenacet concentration in river water with an R2 of 0.61 and an ENS of 0.65.