The effect of future global warming on the seasonal snow cover and runoff is evaluated in the Rio Grande basin at Del Norte, Colorado for average (1976), low (1977), and high (1979) runoff years. Precipitation data are extrapolated to the respective elevations of the basin by taking into account the snow accumulation obtained from snow cover mapping by satellites. Snow covered areas are used as one of the input variable for the Snowmelt Runoff Model. In order to derive the climate-affected snow covered areas of the future, the decrease of the areal snow water equivalent on 1 April is computed and used to derive new snow cover depletion curves indicative of the accelerated snowmelt in the warmer climate. Day-by-day runoff computations using present temperatures and temperatures increased by +4°C reveal a short-term and seasonal redistribution of runoff which differs according to the character of the selected hydrological years. Winter runoff approximately doubles in 1976 (+ 107%), considerably increases in 1976 (+ 60%), and slightly rises in 1977 (+ 22%). The summer runoff consequently declines in all years, but the seasonal runoff peaks are shifted to earlier in the spring as a result of an earlier beginning of the snowmelt season in the warmer climate.