HR: 1340h
AN: H23A-1114    [Abstracts]
TI: Relationship between spatial distribution of the streamwater chemistry and catchment-scale geomorphic characteristics: Conceptual model approach focusing on subsurface and groundwater interaction
AU: * Ohte, N
EM: nobu@bluemoon.kais.kyoto-u.ac.jp
AF: Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Mimasu, Y
EM: ymimasu@kais.kyoto-u.ac.jp
AF: Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Asano, Y
EM: yasano@uf.a.u-tokyo.ac.jp
AF: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan
AU: Uchida, T
EM: uchida-t92rv@nilim.go.jp
AF: National Institute for Land and Infrastructure Management, 1, Asahi, Tsukuba, 305-0804 Japan
AU: Fujimoto, M
EM: fuji@kais.kyoto-u.ac.jp
AF: Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Katsuyama, M
EM: katuyama@kais.kyoto-u.ac.jp
AF: Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Kawasaki, M
EM: kawasaki@kais.kyoto-u.ac.jp
AF: Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan
AB: In order to clarify the mechanisms determining the spatial distributions of streamwater chemistry, a conceptual model explaining the relationship between spatial variability of geochemical solute concentration among the streams and subsurface-groundwater mixing in each subcatchment was proposed. The model assumes that the stream solute concentration is controlled by mixing ratio of subsurface and groundwaters. The variability of solute concentration among subcatchments is potentially generated by difference in the ratio of catchment size of subsurface and groundwaters. The model was applied to the field data taken from two watershed having different geologic settings (granitic and sedimentary bedrock) in central Japan. Variability in geochemical solute concentrations was largest among smallest subcatchments in the most headwaters, and decreased with increasing of subcatchment size. Subsequently the solute concentrations converged into a constant value at the specific catchment scale. Two watersheds have a different converging subcatchment scale. Simulations based on these two field cases suggest that the size of geomorphologically minimum subcatchments (zero-order catchments) at the most headwaters and the variability of solute concentrations among these subcatchments are key parameters determining the size of the converging catchments. Both tow key parameters were larger in the sedimentary rock watershed than the granitic rock watershed, and the size of converging subcatchment was also larger in the sedimentary watershed. It is considered that the difference in geological setting affects the difference originally in the geomorphological characteristics such as valley shape and size of minimum subcatchments at the most headwaters. Consequently, this difference causes the variation in the size of converging subcatchments. The size of converging subcatchment can be treated as an expression of the representative elementary area (REA). The field data suggest the possibility for identifying REA by measuring the geochemical solute concentrations along the stream orders. Moreover, the model approach in this study imply that the determining mechanisms of REA can be generalized by 1) the size of minimum subcatchments at the most headwaters, 2) the variability of geochemical solute concentration among minimum subcatchments, and 3) size of converging subcatchments.
UR: http://www.bluemoon.kais.kyoto-u.ac.jp/site-eg.html
DE: 1719 Hydrology
DE: 1824 Geomorphology (1625)
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1615 Biogeochemical processes (4805)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting