Seven scenarios of global warming were simulated to estimate the effect of snowfall in winter (November -April) in Japan. Each scenario was defined as changes in air temperature and precipitation. Using previously reported values of discriminating temperature, digital maps of daily temperature and precipitation, the form of precipitation could be determined on a daily basis for the entire grid map of daily precipitation . Finally, the digital maps of monthly snowfall and rainfall under each

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... ario were obtained. As a result, mass of snowfall in Japan was estimated at about 131.9 billion tons for the average condition (Scenario No . 1). By increasing air temperature, the absolute value of snowfall may decrease all over Japan and ratio of snowfall to total precipitation in winter may also decrease. For the minimum case, 54.9 billion tons of snowfall was estimated (Scenario No. 7). This decrease in snowfall should result in a decrease in snowcover and snowmelt water during spring. Consequently, there may be increasing water shortages, especially in the regions which even now have low snowfall . Thus, it is necessary to estimate the effects of global warming on the water balance of watersheds in near future.