INTRODUCTION On the Prairies, snow represents the main and vital source of the manageable fresh water supply. In these semi-arid regions, in the ab sence of severe, localized thunder storm activity, melt released by snow accounts on the average for approxi mately 80 to 85 percent of the surface runoff volumes. Thus, this water represents the major component available for storage in dugouts and sloughs. Similarly the rate of melt release from shallow Prairie packs may pro duce flood peaks important to the design of hydraulic structures. Packs that cause flood peaks usually de velop during melt-free winters and are retained until late in the season when climatological conditions favor high melt rate. Factors contributing to rapid melt rates and high dis charge rates are: (a) the pack is shallow and has little capacity to store heat, consequently it reaches isothermal conditions very rapidly; (b) the soil temperature is generally less than 32°F, often resulting in low infiltration rates; and (c) consider able heat flux may be advected to the pack from adjacent fellow land.