Forecasting natural runoff in relation to pumping for irrigation

An illustration is cited of the economic value of snow survey water supply forecasting, for an irrigation project dependent upon reservoir storage from snow melt or pumping from the Flathead River with a fixed maximum load rate. The lower the maximum load, the lower the yearly power rate. Water supply forecasting is accomplished using snow survey courses in the Mission Range in western Montana, and other hydrologic variables, temperature and fall precipitation. A series of multiple regression formulas were developed for forecasts to be made on March, April, May and June. In the spring of 1950 cold weather delayed the runoff well beyond the usual May and June dates. Low snow had disappeared into the soil and the prospects for sufficient snow water looked bad, even in the face of snow survey data for April showing an above normal water content. Starting the pumps would throw the power rate for the year into the highest bracket. Faith in the forecasts prevailed, and on July 2 warm temperatures arrived, canals and reservoirs were full and all reservoirs were filled in one week. Actual money savings of $35,000 in power bills was made.