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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />o <br />(,:~) <br />~.::) <br />W <br />W <br />,... <br /> <br />Consumptive Uses and Losses <br /> <br />10 <br /> <br />Private Water Systems.-The estimated 1990 population served by private <br />community systems on the Navajo Reservation was 515. Assuming a <br />consumptive use rate of 160 gpcd, the annual water use for 1990 was <br />90 (:t30) acre-feet. The uncertainty is estimated as 30 percent of the total. <br /> <br />Individual Wells and Hauling.-According to census data from the Division <br />of Community Development of the Navajo Nation, approximately 17 percent of <br />the study area's population on the reservation (about 6,610 persons in 1990) <br />receives a domestic water supply from individual wells. A consumptive use of <br />90 gpcd was derived as being an accurate water use rate. Based on these <br />figures, the annual consumptive use was 670 (:t200) acre-feet for 1990. <br /> <br />Another 17 percent of the population has no local water supply and must haul <br />its domestic water. In this case, a consumptive use rate of 40 gpcd was applied <br />to an estimated 1990 population of 6,610. The annual consumptive use, then, <br />is 300 (:t90) acre. feet for 1990. The uncertainty for both domestic well and <br />hauled water supplies is estimated as 30 percent. <br /> <br />Total Municipal and Domestic Water Consumption <br /> <br />The total municipal and domestic water consumption, displayed in table 2, is <br />the sum of the individual components discussed in the previous sections. <br />Municipal and domestic water consumption represents approximately <br />20 percent of the total use in the study area. <br /> <br />It is questionable whether all the water pumped from wells should be <br />considered a depletion to the Colorado River; however, it is assumed that <br />100 percent of the water pumped is considered lost to the basin. It is <br />proposed that a future joint study be completed by the Bureau of Reclamation <br />(Reclamation), the State of Arizona, and the Navajo Nation to estimate what <br />percentage of water pumped could actually be attributed to the Colorado River <br />System and would have affected the riverflows for a particular year. <br /> <br />Livestock Water <br /> <br />The source of most livestock water in the study area is from wells, with <br />windmill-operated pumps developed and maintained by Navajo WOM, and <br />water collected in small surface ponds. From information provided by the <br />Navajo Nation for previous studies regarding pumping rates and periods of <br />operation, an estimated 1,500 acre-feet of water per year was assumed to be <br />pumped from wells for livestock. This quantity compares to 1,100 acre-feet <br />estimated from agricultural statistics of the amounts of livestock that are in the <br />