ASSESSMENTS OF SWAT FOR WATER QUALITY MODELI NG INWATERSHED HAVING PADDY FIELD: CASE STUDY IN UPPER KASHIMA RIVER, JAPAN

摘要

Soil and Water Assessment Tool (SWAT) is a very promising to simulate stream fl ow and waterquality in an agricultural watershed. Many studies have reported that it can give acceptableresult to assess non-point source pollution. In Kashima River, SWAT application is expected toaid the planning process in mitigating non-point source pollution, by means of environmentalconservation scenario development. As the fi rst step towards investigating the applicabilityof SWAP in the Kashima River basin in Japan, the present study was conducted. SWATmodel was confi gured using ARC-SWAT 2009 and calibrated using SUFI-2 method. Modelevaluation was done by interpreting calibration results using the information gathered from thefi eld and literatures. This study showed that SWAT can model stream fl ow well, regardless of itsdifferent model structure, under a real-life paddy fi elds process. However, nitrogen simulationwas not satisfactory. This is mainly due to complicated processes in ponded storage, watermovement into the soil, ground water fl ow and denitrifi cation.