Sustainability of Groundwater Resources and its Indicators (Proceedings of symposium S3 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 302, 2006, 158-171.

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Analysis of NO₃-N pollution with a distributed groundwater quality model

Hiroaki SOMURA¹, Akira GOTO², Hiroyuki MATSUI², Elhassan Ali Musa³ & Masakazu MIZUTANI²

1 National Institute for Rural Engineering, River and Coast Laboratory, Kan-nondai 2-1-6, Ibaraki 305-8609, Japan

somura@nkk.affrc.go.jp

2 Faculty of Agriculture, Utsunomiya University, Minemachi 350, Tochigi 321-8505, Japan

3 Interstate Stream Commission, Santa Fe, New Mexico 87504-5102, USA

Abstract Nitrate-nitrogen (NO₃-N) was selected as a groundwater resource sustainability indicator because it is well known as a cause of some diseases and the concentration in groundwater has increased gradually in recent years. We monitored it continuously from August 1996 to December 2001 in the Nasunogahara basin, Tochigi Prefecture, Japan, and constructed a distributed groundwater quality model in this basin. The model consists of two processes: infiltration of the NO₃-N load into groundwater, and advection of the NO₃-N load in the groundwater. As a result, the large changes of nitrogen load in the surface layer before/after heavy rainfall and the concentration changes in the groundwater by advection were well expressed. In addition, the effects of the nitrogen load infiltration from many livestock farms in the upper basin to groundwater in the lower basin were investigated.

Key words alluvial fan; livestock farming; shallow aquifer; sound utilization of groundwater

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