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Tile uF'allu Val ley, as tine vai iey confluence area is called, is classified <br />as arrid with a mean annual precipitation of eight inches and a mean annual <br />temperature of 52% F. <br />The study section of river is considered a warmwater fishery from a <br />resource management point of view. Temperatures of 800F. (270C) occur at <br />times. This temperature approaches the upper limits that coldwater game fish <br />such as trout can tolerate. <br />Agriculture is the main industry throughout the valley, being orchards <br />in the upper valley and small grain and forage in the lower valley. A <br />description of geology and flora and fauna is presented in the report Flora <br />and Terrestrial Vertebrate Studies of the Grand Valley, Colorado (Bureau of <br />Reclamation, 1976). <br />Because of the high demand for water, both for agriculture and domestic <br />use, a large amount of river water is diverted. Two large rock diversions <br />and a permanent concrete diversion are located on the Gunnison River. The <br />concrete Redlands Power Diversion, used for power generation and irrigation, <br />is located 12 miles above the mouth of the Gunnison River. Built in 1907, <br />it spans the entire width of the river and is considered an effective fish <br />migration barrier. The other structure is approximately 28 miles upstream <br />at the Broughton Orchard area and should not be considered as a barrier to <br />fish migration. There are also a number of smaller ditches and irrigation <br />pumps taking water from the river. On the Colorado River there are three <br />major diversion structures and many smaller pumping stations. The largest <br />of the three, the Government Highline Canal, uses a roller dam to divert <br />water. During most periods of the year, this is an effective fish migration <br />barrier. The second structure, called Palisade Irrigation District Diversion <br />is considered an effective fish barrier at all times. The third diversion, <br />(5)