HR: 0800h
AN: H11C-0635    [Abstracts]
TI: Geochemical baseline survey based on streamwater chemistry of small mountainous watersheds in the Kanamaru area, Japan
AU: * Okuzawa, K
EM: koichi-okuzawa@aist.go.jp
AF: : National Isntitute of Advanced Industrial Science and Technology, Tsukuba Central 7, 1-1- 1 Higashi, Tsukuba, 305-8567, Japan
AU: Seki, Y
EM: yoji-seki@aist.go.jp
AF: : National Isntitute of Advanced Industrial Science and Technology, Tsukuba Central 7, 1-1- 1 Higashi, Tsukuba, 305-8567, Japan
AU: Naito, K
EM: naito-k@aist.go.jp
AF: : National Isntitute of Advanced Industrial Science and Technology, Tsukuba Central 7, 1-1- 1 Higashi, Tsukuba, 305-8567, Japan
AU: Kamei, A
EM: kamei-a@riko.shimane-u.ac.jp
AF: Interdisciplinary Faculty of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue, 690-8504, Japan
AU: Takeno, N
EM: n.takeno@aist.go.jp
AF: : National Isntitute of Advanced Industrial Science and Technology, Tsukuba Central 7, 1-1- 1 Higashi, Tsukuba, 305-8567, Japan
AB: It is generally known that all of the natural river water is supplied from groundwater under base flow condition. The variety of groundwater chemistry is caused by various factors such as the chemistry of aquifer and residence time, which are mainly controlled by the lithology and geological structure of the watershed. The quality of river water under base flow condition therefore reflects the lithology and geological structure of the watershed. There is an example which draws high resolution hydrogeochemical baseline map of large area in England based on the water quality of first and second order streams (average of catchment areas: 1.75km2). This mapping was conducted in dry summer season, which is essential to have successful result in this type of mapping. To conduct similar mapping in Japan, much attention has to be paid on hydrological condition to the measurement, because we do not have clear dry season in Japan. Main target of this study is to show hydrological condition on which successful mapping stands. We examined the relationships between the water quality and discharge of several small streams in the Kanamaru area, NE Japan, under various water level conditions. The water-quality parameters and concentrations of dissolved elements presented specific values under lower water level condition from base flow to low water discharge of about three times of base flow. Therefore, hydrological survey for the hydrogeochemical baseline mapping can be conducted under lower level condition when the discharge does not exceed three times of base flow in the watershed of Kaminosawa Stream. On the basis of these results, we investigated the water chemistry of 63 streams, their watershed are 0.5–2.0 km2 wide (average: 1.0 km2), under low water conditions, and tried to draw a hydrogeochemical baseline map around the Kanamaru area. We report the preliminary results of hydrogeochemical mapping around the Kanamaru area, and discuss its usefulness.
DE: 1000 GEOCHEMISTRY
DE: 1022 Composition of the hydrosphere
DE: 1039 Alteration and weathering processes (3617)
DE: 1800 HYDROLOGY
DE: 1806 Chemistry of fresh water
SC: Hydrology [H]
MN: 2007 Fall Meeting