RIVER WATER QUALITY ANALYSIS ON CHANGES IN DAIRY FARMING CONDITIONS AND ITS SURROUNDING ENVIRONMENT USING SWAT

Abstract

 The farming conditions in the large-scale dairy area of eastern Hokkaido are changing due to the implementation of an environmental conservation-type irrigation and drainage project and crop conversion following climate changes. Changes in the outflow routes of water pollutants and subsequent changes in nitrogen cycle are consequently predicted, and it is necessary to quantify the impact on the water quality environment in the entire basin scale. In this study, we applied SWAT, a semi-distributed model, to small-scale watershed, and analyzed river water quality assuming farming conditions in three periods, namely, the past, present, and near future. The results showed an increased nitrogen load of the surface flow due to the conversion from pasture to silage corn, but surface, lateral and groundwater flow could all be reduced by arranging project facilities in and around the converted farmland.