[A-HW18] Isotope Hydrology 2016

[AHW18-P01] On stable isotope ratios of water in the Fuefuki River,
Yamanashi Prefecture, Japan

*Akihiro Sasaoka¹, Takashi Nakamura², Genki Nakanishi³ (1.Department of Environment Systems,Faculty of Geo-enviromental Science,Rissho University, 2.International Research Center for River Basin Environment, University of YAMANASHI, 3.Special Master Course Program on International River Basin Environmental Science The University of Yamanashi)

Keywords:Fuefuki River, stable isotopes, rivers recharge

This study is carried out to make clear the changes in stable isotope ratios of water of the Fuefuki River. The Fuefuki River is originating from the Kanto mountainous district located in the northeastern part of Yamanashi Prefecture, and it flows along the south-eastern edge of the Kofu basin.
The results of the analysis are as follows.
At the upper reaches of the Fuefujki River, the values δD are influenced by ” the altitude effect of rainfall”, and at the down reaches area, the valuesδD are gradually become larger, i.e. heavier than the water of the upper reaches. δD of the water in the bottom of Kofu basin, downstream area of the Fuefuki River, is more heavier than that of upper reach of the river, However, between St.3 andSt.4, and between St.6 and St.7, the values of δD at the downstream points are smaller.
These changes is not possible to explain by altitude effect, and the authors pointed out that there are two type of inflow to the Fuefuki River, one is tributary stream with high mountain basin area, and the other is groundwater discharge to the Fuefuki River near the outlet area of the Kofu basin.