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CHAPTER IV UTILIZATION OF AGRICULTURAL WATER RIGHTS I The two important measures of injury are a change in the depletion of the stream and a change in the timing of the flows. The depletion is usually measured in terms of historic CU. Initially, this may not appear to be an issue for the Recovery Program since an instream flow does not "consume" any water. But moving a larger volume of water than the historic CU of a water right could have injurious affects on water users between the historic location and the Reach. For example, if the Recovery Program purchased a 30 cfs direct flow right in the Glenwood Springs area that had historically irrigated 1,000 acres and consumed 2,000 AF of water. Over a 200-day growing season, this acreage consumed water at the rate of 5 cfs. Of the remaining 25 cfs, a small portion evaporated, some may have entered a non-tributary ground water system, but the majority of the water eventually returned to the river. The portion that returned to the river was available to the irrigators downstream. To prevent injury, the only portion of the water right which could be transferred to the Reach was the portion that was consumed. Generally, CU per irrigated acre decreases as the elevation of the irrigated field increases. The CU for alfalfa in the Grand Valley is about 40 inches/year/acre. Subtracting the usable precipitation, the net CU is 36 inches/year. From the Grand Valley, proceeding upstream, the net use for alfalfa at, Rifle is 31 inches, New Castle 24 inches, Glenwood Springs 23 inches, and Eagle is 17 inches.' To focus the Recovery Program on those areas which have the highest potential of providing CU, an arbitrary decision was made to restrict the search to those areas which had a net CU of about 50 percent of that found in the Grand Valley. Eagle, Colorado, is in the Soil Conservation Service's climatic zone 5.2 The climatic zone is an indication of CU, as the climatic zone number increases the CU decreases. Grand Junction is in climatic zone 1. Only those water rights within the climatic zones 1 through 5 were selected. The timing of the CU occurs earlier in the year as elevation increases. The peak consumption rate for water rights in climatic zone 5 is in July and decreases by 60 to 70 percent by September. Consequently, the ability to transfer water from zone 5 areas will be further limited by timing of use. These rights can be divided into three categories: those upstream and junior to the Cameo call, upstream and senior to Cameo, and the rights at Cameo. Roughly 2,260 cfs of water at the Cameo gage is required to meet all of the irrigation and power demands in the valley (1,620 at the Cameo diversion and 640 for GVIC). With the current operation of the ' U.S. Department of Agriculture. Soil Conservation Service. Colorado Irrigation Guide, 1978 and 1988. 2 Ibid. I 22