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<br />energy for snowmelt. The conduction of heat energy from the underlying <br /> <br /> <br />ground to the snowpack has little effect on daily snowmelt quantities, <br /> <br /> <br />however, this process may be important in terms of priming the soil surface <br /> <br />prior to the actual melt season. The amount of heat yielded to the <br /> <br /> <br />snowpack by rain water is largely dependent upon the temperature of the <br /> <br /> <br />rainwater. Also, the freezing of rain water in the snowpack releases heat <br /> <br /> <br />energy (latent heat of fusion,80 calories per gram) to the snowpack. <br /> <br />Section 3.05 Snowpack Condition <br /> <br />Snowmelt at any point in time is highly dependent upon the condition <br /> <br /> <br />of the snowpack as well as the heat energy flux. The snowpack condition <br /> <br /> <br />is generally identified in terms of its "cold content" and its water- <br /> <br /> <br />holding capacity or liquid-water deficiency. Basically, energy is required <br /> <br /> <br />to raise the snowpack temperature to 320F (OOC) and to melt enough snow <br /> <br /> <br />to satisfy the water-holding capacity of the snowpack before liquid water <br /> <br /> <br />can reach the soil surface. Once these conditions are met, the snowpack <br /> <br /> <br />is considered to be "ripe" and any additional energy input to the snowpack <br /> <br /> <br />causes snowmelt runoff. Although these properties of a snowpack are <br /> <br /> <br />difficult to quantify in a practical sense, some assessment of snowpack <br /> <br /> <br />condition is needed to predict the proper timing of snowmelt runoff. <br /> <br />Section 3.06 Snowmelt Equations <br /> <br />The complexity of the snowmelt process coupled with a general lack of <br /> <br /> <br />energy budget data, necessitates the use of rather simplified mathematical <br /> <br /> <br />equations to estimate snowmelt. The type of equation used in most instances <br /> <br />is determined as much by data availability as by the basin and storm <br /> <br /> <br />characteristics. Numerous snowmelt equations, their development, and exam- <br /> <br /> <br />ples of application are presented in references 3.04 and 3.05. <br /> <br /> <br />When energy-budget data are available in sufficient quantity and <br /> <br /> <br />quality, the generalized snowmelt equations can be used. For example, <br /> <br /> <br />snowmelt during a rainstorm for an open or partly forested basin can be <br /> <br /> <br />computed by the following equation if English units are used: <br /> <br />3-05 <br />