| The chemical and biological attributes of streams are highly related to watershed characteristics, and land use has been identified to exert a major effect on water quality. Close relationships between agricultural land uses and nitrogen (N) fertilizer loading in a drainage basin with nutrient concentrations in stream and subsurface water have been reported in several studies (Hayashi & Hatano, 1999). Thus, this study was carried out to evaluate the effects of fertilizer nitrogen (N) and phosphorus (P) loading on quality of riverine and groundwater through surface runoff and leaching in Yata River Basin in Ibaraki Prefecture, Japan, using WEP distributed hydrologic model coupled with a basin-wide nutrient dynamics model (Jia et al, 2002;, Kinouchi et al., 2004) and fertilizer input data compiled with a GIS based application (Iizumi et al., 2007). The annual percentage loading of fertilizer dissolved N and P into the downstream Ushiku Lake was estimated using the modeling approach, in an attempt to acquire basic understanding to develop integrated, basin-wide management practices for environment-friendly agro-ecosystems in rapidly urbanizing watersheds. |
