Application of a simple snowmelt-runoff model to large river basins

The snowmelt-runoff model (SRM) developed by Martinec (1975) for use on small mountain basins (<50 sq km) has recently been extended to large river basins (200 -4000 sq km) using remotely-sensed snow-cover data. In addition to the snow-cover data obtained from satellites, the model only requires the input of daily temperature and precipitation data. For model operation, the following parameters must be determined: degree-day factor, runoff coefficient, recession coefficient, temperature lapse rate, and discharge time lag. Simple procedures allow use of SRM in a variety of conditions including rain on snow situations. The average absolute error between actual and simulted runoff volume for the snowmelt season for nine large basins was 3 percent. The average Nash-Sutcliffe R square value, which measures the daily flow fit, for the large basins was .85. In general, the simulation results tend to degrade as the quality of input data decreases which in most cases occurs as basin size increases. Techniques are currently being developed for using SRM in the forecast mode. To aid in application of SRM to a basin, a user manual is now available along with a sample data set for computer implementation.