The water quality investigation of seepage water around Misogawa dam has been conducted for more than six years since the start of the initial filling of the reservoir. The investigated data show the water quality was affected by the intrusion of reservoir water to the rock mass around the dam. The electric conductivity (EC) which represent the water quality gradually evolved according to the filling of the reservoir. The evolution of EC was modeled considering the advection and water-rock reaction. The hydraulic conductivity was estimated by curve matching relevant to the measured EC using the EC model simulation. The simulated results and the measured data show good agreement and the estimated hydraulic conductivity was acceptable value. The result of applying the EC model to this site presents the availability of the model and the efficiency for estimating the hydraulic conductivity.
