Uncertainty reduction of hydrologic models using data from surface-based investigation

地上からの調査段階における水理地質モデルの不確実性低減について

唐崎 建二*; 伊藤 一誠*; Wu, Y.*; 下茂 道人*; 澤田 淳 ; 前川 恵輔  ; 畑中 耕一郎

Karasaki, Kenji*; Ito, Kazumasa*; Wu, Y.*; Shimo, Michito*; Sawada, Atsushi; Maekawa, Keisuke; Hatanaka, Koichiro

We present some examples of using information other than pressure data to constrain the model. The initial model was constructed using information from surface geology and a few boreholes. Inversion analysis of pressure implied the existence of a low-permeability rock. We then used river flow data and temperature data from a hot spring as a basis for estimating the recharge flux, which suggested that the overall permeability of the modeled area could be one order of magnitude larger than that of the base model. Next, we simulated a saltwater washout process and compared the simulated salinity distribution with the salinity data from a borehole. We found that a better match to the salinity data is obtained if the increase of permeability is taken up by the fault zone rather than uniformly by the entire model. A smaller-scale match to the temperature, pressure, and density profiles from two boreholes indicated that there was a low permeability fault in between the two boreholes.