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Show PARC II DESCRIPTION OF REGION Climate The climate in the Upper Colorado Region is semiarid to arid and con- sists generally of four seasons. Wide variations in precipitation, tem- perature, and wind movement result primarily from varied topography and to a lesser extent from the rather wide range in latitude. Average annual precipitation ranges from less than 6 inches in the lowest valleys to more than 50 inches in the higher mountains while that in most valleys and agricultural areas varies from 10 to 20 inches a year. (See map following page lk ,) Precipitation from late October through mid-April consists primarily of snow, particularly at higher elevations. Snow accumulations occasionally exceed 100 inches at the higher elevations and do not completely melt until late summer. Temperatures vary widely with extremes being recorded from -60° F. at Taylor Park, Colorado, to 115° F. at Lees Ferry, Arizona. Mean monthly temperatures are lowest in January and highest in July and generally show about 50° F. seasonal difference. The average frost-free period or con- secutive period with temperatures above 32° F. varies from 20 days or less at elevations above 8,500 feet to more than 180 days at elevations below 5,000 feet. The growing season is slightly longer than the frost-free period for the grass and alfalfa crops which predominate on the higher elevation lands. Winds over the region move generally from west to east, but the wind movement is greatly modified by local topographical influences. Average annual wind velocity varies from about 8 to 1^4 miles an hour while strong winds associated with local thunderstorms have reached velocities of 80 to 90 miles per hour. Annual evaporation from lakes and reservoirs is estimated to range from less than 30 inches at higher elevations to about 60 inches in the lower valleys. Geology and Topography The region is comprised of highly dissected mountainous plateaus, typified by deep canyons, river valleys, rolling ridges, and flat-topped mesas. It is rimmed on the east, north, and west by high mountains. Ele- vation varies from 3A00 feet at Lee Ferry, Arizona, to more than 1^4,000 feet at some of the higher mountain peaks. The Colorado Rocky Mountains--including the San Juan Mountains on the south end of the region--are impressive from both a scenic and geo- logic viewpoint, as are many other mountain ranges in the region. Sparsely vegetated plains predominate at lower elevations. Above 8,000 13 |