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<br />'FRYINGPAN"ARKANSAS PROJECT, COLORADO
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<br />7
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<br />create a risk in meeting the Lee Ferry obligation of the Colorado
<br />River compact.
<br />18. Irrigation,-The main agricultural part of the eastern slope
<br />project area is in the semiarid zone of 11 to 16 inches of annual pre-
<br />cipitation. Seventy to eighty-six percent falls during' the April to
<br />October growing season. Dry farming is and probably will continue
<br />to be practiced extensively. Livestock grazing on the ranges and in
<br />the forests is also an extensive enterprise. However, hoth types of
<br />agriculture require large land areas, and dry farming particularly
<br />depends upon the vagaries of the weather. General cultivated agri-
<br />culture find specialty high-value crops, many of which are required to
<br />stabilize the agricultural eeonomy of the area, Tequire more water
<br />than typical dryland crops, Irrigation is the only means of providing
<br />a dependable supply,
<br />19, Early irrigation in the Arkansas Valley coincided with available
<br />stream run-ofL As ready markets developed, irrigation farming was
<br />expanded and a demand developed for la.te season water which could
<br />not be supplied by unregulated streamflow, Consequently, between
<br />189(}.and 1910, three reservoirs in the headwaters area and 11 off"
<br />stream reservoirs below Pueblo weTe con~ructed, In 1949 the John
<br />Martin Reservoir on the Arkansas River was completed by the Corps
<br />of Engineers for conservation storage and flood eontrol. It also has
<br />an irrigation storage space of 420,000 acre-feet. The t.hree headwaters
<br />reservoirs have a capacity of 84,400 acre-feet. The 11 off-stream
<br />reservoirs have a present. capaeity of 300,000 acre-feet which repre-
<br />sents about 75 percent of the original capaeity as a consequenee of
<br />sedimentation. Eight privately owned trallsmountain diversion sys-
<br />tems import about 48,000 acre-feet annually,
<br />20. More than 40 canals and ditches supply irrigation water to lands
<br />in 1,he valley between Canon City and the Colorado-Kl1nsas boundary.
<br />Sediment deposition in canl1ls and ditches has become a major irrigation
<br />problem in the Pueblo-Las Animas reach. In some instances long
<br />reservoir feeder canals have lost 50 percent of their capacity because
<br />of sedimentation,
<br />21. The amount of irrigation water available for the 322,000 acres
<br />of irrigated land in the project area varies eonsiderably from year to
<br />year, Seldoinis the supply adequate for maximum crop production,
<br />Irrigation water shortages as high as 78 pcrcent of crop requirements
<br />have oecurred. The estimated average canal headgate. diversion re-
<br />quirement is 3.19 acre-feet an acre, Allowing for tolerable shortages,
<br />that headgate requirement can be reduced to 3,10 acre-feet. The
<br />average amount of seasonal irrigation water historically available
<br />bctween Pueblo and the Kansas State line hl1s ranged from 0,9 acre-
<br />feet an acre in 1934 to 2.7 acre-feet in 1942, The base flow of every
<br />stream in the valley is overappropriated, Enhancement of the irri-
<br />gation water supply depends upon regulat,ion of eJ.'isting supplies for
<br />more efficient use, additional storage capacity for the conservation
<br />of excess flood flows, reservoir space for holdover storage, and new
<br />water supplies for which the only apparent source is transmountairi
<br />diversion from the Colora.do River drainage, "
<br />22. Power.:-"'Power facilities of the initial development will be de~
<br />signed for integration with the power facilities of the Bureau's Colo~
<br />rado-Big Thompson project and with local utilities to serve 11 com-
<br />bined powel' rriarket area. The combined area, which consists of the
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