HR: 0800h
AN: H21C-1365    [Abstracts]
TI: Groundwater Flow Model Including Deeper Part On The Basis Of Field Data - Especially Determination Of Boundary Conditions And Hydraulic Parameters-
AU: * Machida, I
EM: imachida@onken.odawara.kanagawa.jp
AF: Hot Springs Research Institute of Kanagawa Prefecture, 586, Iriuda, Odawara, Kanagawa, 250-0031 Japan
AU: Itadera, K
EM: itadera@onken.odawara.kanagawa.jp
AF: Hot Springs Research Institute of Kanagawa Prefecture, 586, Iriuda, Odawara, Kanagawa, 250-0031 Japan
AB: The final purpose of our study is to clarify the quantitative groundwater flow including deeper part, 500-1000m depth, in the basin in caldera on the mountain. The computer simulation is one the best methods to achieve this purpose. In such a study, however, it is difficult to determine the boundary conditions and hydraulic properties of geology in deeper part, generally. For this reason, we selected Gora basin as a study area, because many hydraulic data have been stored for more than 30 years in this basin. In addition, because the volcanic thermal water is mainly formed by mixing of groundwater and thermal component, the study for deeper groundwater flow can contribute the agenda for the protection of thermal groundwater which is regards as a limited resource. Gora basin, in Hakone area is one of the most famous spa (a resort having thermal groundwater or hot springs) in Japan. The area of the basin is approximately 10 square kilometers and has more than 200 deep wells. In our study, at first, the dataset of hydraulic head was created by using the stored data to construct the conceptual model for groundwater flow. The potential distribution exhibited that the groundwater flowed downward dominant. And the geomorphology can be regarded as hydraulic boundary even in deer part, that is to say, we can regard the ridge as no flow boundary in simulation model. Next, for quantitative understanding of groundwater flow, we need to obtain not only boundary conditions but also hydraulic property of geology, for example, hydraulic conductivity, K, as one of the important parameters. Generally, such a parameter has not been measured in past survey. So, we used the belief method for calculating the hydraulic conductivity by using the data of thermal logging test, which was similar to a slug test. As results of the analysis, the close relationship between K and well depth were obtained. This result implies that the K value depends on the overburden pressure of geology. That is to say, we should take the well depth into consideration, when we give the K value to geologic layer in the simulation model.
DE: 1828 Groundwater hydraulics
DE: 1829 Groundwater hydrology
DE: 1847 Modeling
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
DE: 8440 Calderas
SC: Hydrology [H]
MN: Fall Meeting 2005