The Impact of Nitrogen and Phosphorus Fertilizer Loading on River and Subsurface Water Quality in Yata River Basin: An Integrated, Basin-wide Modeling Approach

Abstract

This study was carried out to evaluate the effects of fertilizer nitrogen and phosphorus surplus loading on riverine and subsurface water quality in Yata River Basin in Ibaraki Prefecture, Japan. Fertilizer input data was compiled with a GIS based application while apportionment and subsequent transport of surplus nutrients into river network and leaching into groundwater layers was achieved using WEP distributed hydrologic model coupled with a basin-wide nutrient dynamics model. The results depicted that significant fraction of surplus dissolved nutrients are transported to the river networks and a part leached into the groundwater layer, implicating resultant water quality degradation in the ecosystem.