[AHW32-P10] Effect of groundwater recycle system on nitrate load distribution in an agricultural area, Japan
Keywords:groundwater recycle, nitrate load, SWAT model
In this study, we estimated nitrogen load from the catchments in Ikuchijima island using the SWAT (Soil and Water Assessment Tool) model. Especially, we tried to simulate the effect of reducing fertilizer application on nitrogen load assumed the recycle of NO3- in groundwater. The results showed that NO3- loads were highest near the coastal areas, which is related to the distribution of citrus farms. 42% of nitrogen load was from citrus farms in the north region of the island, and it ups to 60 % in the south region. It indicates fertilizer is the major source of nitrogen load in the island. Higher average nitrogen loadings also occurred in high density of residential area. The total nitrogen load from whole island was estimated to be 82507kg/yearwhen the annual nitrogen fertilizer application is 240kg/ha/year. However, it decreased to 42548kg/year when the fertilizer application was reduced to 160kg/ha/year.