The primary causes of water temperature rising is not only climate change but also land-use alteration by human activities. The Kushiro River watershed is representative nature restoration site in Japan. From ecological aspect however, the seasonal dynamics of water temperature has not been monitored in the before-after assessment. So, we focused on the water temperature simulation by using watershed hydrological model. Then, we adopted future land-use scenario in 2050 as initial condition to this model. The objectives of our study are following two.1) We set up some future scenarios (in 2050) to this watershed and developed simulation model to forecast the water temperature change.2) To evaluate the impact of land-use change on water temperature and the aquatic ecosystem. As the result of this approach, we calculated the water temperature change though the year. Then we discussed the actual plans that we should start with local stake holders.