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OOOl~8 etc. The metamorphic and metasedimentary (partially metamorphosed sedimentary) r.ocks include quartzite, a variety of schists. The third area of bedrock in the study area is sedimentary deposits located along the lower two-thirds of the Jack Creek drainage. These sedimentary deposits consist of marine aod nonmarine formations of sandstones, shales, con- glomerates, and alluvial deposits of sands, silts, clays, and gravel. C. Climate Climatological data gathered in the study period from 1940 to 1978 indicate annual precipitatioD in the study area is 12.6 inches at Dixon. About 6 inches fall during the growing season in the Dixon-Baggs area. The higher elevations of the Sierra Madre Mountains occasionally receive as much as 35 inches precipitation per year, th2 majority coming as snowfall. The average ~nnual temperature at Dixon is 41.8DF with a monthly range from 17.30F to 64.50F. The frost-free period or consecutive period with tempera- tures above 320Y averages about 86 days near the Dixon-Baggs area. D. Water Supply The Little Snake River and Jack Creek have their headwaters in the Sierra Madre mountains. The Little Snake River is in the Colorado River drain- age while Jack Creek drains to the North Platte River in the Missouri River drainage. The water supply for all alternatives evaluated in this study relies upon the Little Snake River or its tributaries. Major tributaries of the Little Snake River include the North, Middle, South, ~nd Roaring Forks of the Little Snake River, Battle Creek, Savery Creek, and Slater Creek. The major streams in the area, iDcluding the Little Snake River and Savery Creek, often dry up as a result of irrigation diversions. The majority of lands presently irrigated in the Little Snake River drainage, approximately 76%, depend upon diversions from the main stern of the Little Snake River and from Savery Creek for water supply. III-J