Evaluation of Uncertainties in Hydrogeological Modeling and Groundwater Flow Analyses -Model Calibration-

Ijiri, Yuji*; Ono, Makoto*; Sugihara, Yutaka*; Shimo, Michito*; Yamamoto, Hajime*; Fumimura, Kenichi*

For the purpose of evaluating how uncertainties included in modeling of hydrogeological structure and results of groundwater simulation decreased with progress of investigation research, updating and calibration of the models about several modeling techniques of hydrogeological structure and groundwater flow analysis techniques were carried out, based on the information and knowledge which were newly acquired. The acquired knowledge is as follows.The model calibration is performed by the method of matching numericals simulation with observation, about the pressure response caused by opening and closing of a packer in MIU-2 borehole. Each analysis technique attains reducing of residual sum of squares of observations and results of numerical simulation by adjusting hydrogeological parameters. However, each model adjusts different parameters as water conductivity, effective porosity, specific storage, and anisotropy. When calibrating models, sometimes it is impossible to explain the phenomena only by adjusting parameters. In such case, another investigation may be required to clarify details of hydrogeological structure more.Since it is a little more flexible about boundary condition and faults except Tsukiyoshi fault than last year, travel paths themselves vary a little rather than last year. However, as a result, when travel paths are almost the same, model calibration can reduce the variation of travel length and Darcy velocity among models within about one order. It will be necessary to propose investigation aiming at reducing the uncertainty of data, such as water conductivity and effective porosity and at making hydrogeological structure more detailed from a viewpoint of modeling.