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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 />area, and outsi rle i rri gati on practi ces account for most of thi s rlifference <br />between Cortez and Towaoc usage. A summary of hi stori cal usage in Cortez by <br />month for the period 1973 to 19AO is contained in Appendix 8. <br /> <br />2.3 Water Use Projections <br /> <br />Water use projecti ons are generally made based on popul ati on projecti ons and <br />estimates of per capita water use rates. In addition, to establish a realistic <br />desi gn flow, it is necessary to estimate the difference between the average <br />annual water demand and the peak demand. A design flow should be selected <br />~Ihich, when supplied in conjunction with the use of stored water in treated <br />water reservoirs, is sufficient to provide the expected municipal needs. <br /> <br />2.3.1 Population Projections <br /> <br />Popul ati on projecti ons form the foundati on for water use projecti ons and are <br />often the subject of disagreement among municipal planners. Based on <br />i nformati on provi ded by Steve Harri s, the engi neeri ng representati ve for the <br />Tribe and the Tribal Planning Oepartment, the estimated population served by <br />the Towaoc water supply line in 1987 is 1,330 people. The 1970 and 1975 U. S. <br />Census Oata lists a Towaoc population of 1,175 and 1,335 respectively. <br />Estimates presented in a study by Chapman and Associ ates Engi neeri ng (19851 <br />projected the Towaoc population growth rate to average about 0.8 percent per <br />year. Earlier Bureau projections used during the planning of the Dolores <br />Project estimated an annual growth rate of 2.5 percent. The estimatert future <br />water demands for Towaoc are influenced heavily by the assumed population <br />growth rate. Figure 2.1 shows the population expansion based on one-and tWQ- <br />percent growth rates. <br /> <br />2.3.2 Average Water Use Rates <br /> <br />The Bureau's Feasibility Study for the Oolores Project reconmended 275 gpcd <br />for an average demand for Towaoc. Chapman and Associates Engineering (1985) <br />reported that the ground-water supply on the reservation was capable of <br />providing 175 gpcd for Towaoc, but their own study recommended an average use <br />rate of 220 gpcrl. <br /> <br />2-3 <br /> <br />1059c <br />