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<br />002483 <br /> <br />During the design study, MBA determined that insufficient data <br />existed for a complete and detailed specification of all aspects of <br />the design. In particular, there are mixed orographic and convective <br />processes present in most Sierra Nevada winter storms and the degree <br />to which one dominates as the precipitation formation mechanism at <br />a particular time determines the potential and the appropriate method <br />for modification. However, since it is known that both processes <br />exist at one time or another, MBA said that it is possible to design <br />a program which deals with each when it does dominate. MBA recom- <br />mended dual objectives for the SCPP. These are: <br /> <br />,,_ To develop a better understanding of the physical processes <br />of precipitation formation in the Northern and Central Sierra <br />Nevada leading to identification of those conditions that <br />provide the best potential for snowpack augmentation. <br /> <br />,,_ Through the use of this increased knowledge and incorpor- <br />ating the knowledge gained through the conduct of other pro- <br />grams in the Sierra Nevada and elsewhere, test the feasibility <br />of snowpack enhancement as a means to improve the water resource <br />management and yield in the Sierra Nevada." <br /> <br />Background <br /> <br />MBA said that the general procedure of water management in the <br />Sierra Nevada recognizes two seasonal periods. The first includes <br />most of the winter, in which part of the Folsom Reservoir volume <br />is reserved for flood contingencies by permitting outflow through <br />the hydroelectric generators, spilling the water in excess of <br />generator capacity. The flood control pool is reserved from <br />November through April to accommodate possible winter floodflows. <br />During the second period, May to October, this area of the reser- <br />voir is allowed to fill for conservation purposes, includin9 <br />recreation use. This also is the period of peak demands for agri- <br />culture and domestic needs. <br /> <br />One objective of a snowpack augmentation program is to redistribute <br />the precipitation to snowpacks at higher elevations so that the <br />reservoir outflow not used for electrical generation or other <br />requirements is minimized throughout the year. The ideal situation <br />would be to have the moisture stored in the snowpack to be used <br />during the snowmelt and summer season, rather than being spilled <br />past the hydroelectric generators during winter months. <br /> <br />MBA classified the Sierra Nevada storms in two general categories, <br />which will determine the project's operational criteria: <br /> <br />8 <br />