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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 />. Consumptive Uses and Losses <br /> <br />7 <br /> <br />. <br /> <br />The average annual value of 1,310 acre-feet pumped by NTUA to serve an <br />estimated 1980 population of 12,500 represents a water use Tate of <br />approximately 95 gallons per capita per day (gpcd). This value is considerably <br />smaller than the per capita use rate for surrounding cities. For example <br />Shiprock, New Mexico, averages about 148 gpcd! After reviewing the report <br />"1981-1983 Annual Consumptive Uses and Losses in the Arizona Portion of the <br />Upper Colorado River Basin," the Water Resources Division of the Navajo <br />Nation commented that the figure of 95 gpcd probably underestimates the <br />amount of domestic water used, since water is also available from sources <br />which are not metered. The NTUA estimates an additional 900 acre-feet <br />should. be added to the total supply available to account for the use of <br />unmetered water sources in the NTUA service areas in 1980. This addition <br />increases the estimated per capita consumptive use to approximately <br />160 gpcd.5 For this report, this same rate was used which resulted in <br />900 acre-feet being added and is reflected in table 2 as additional consumptive <br />use for NTUA. Unmetered uncertainties are estimated to be about 30 percent. <br /> <br />o <br />:::l <br />c.) <br />W <br />1\.) <br />QO <br /> <br />Table 2.-Total domestic and municipal consumptive use for 1990' <br /> <br />Page <br />GCNRA <br />Canyon de Chelly <br />NTUA (metered) <br />NTUA (unmetered) <br />BIA (Shiprock) <br />Western Navajo Agency <br />BIA (Chinle) <br />WOM <br />Private <br />Individual Wells <br />Hauling <br /> <br />Total <br /> <br />Consumptive use (acre-feet) <br /> <br />2,060 <br />450 <br />20 <br />1,050 <br />900 <br />70 <br />630 <br />330 <br />550 <br />90 <br />670 <br />300 <br /> <br />7,120 <br /> <br />Estimated <br />uncertainty" (acre-feet) <br /> <br />60 <br />10 <br />10 <br />70 <br />270 <br />10 <br />40 <br />20 <br />170 <br />30 <br />200 <br />90 <br /> <br />400 <br /> <br />1 All numbers are rounded to the nearest ten (10). Values less than five (5) are rounded to zero. <br />2 The calculation of the total degree of uncertainty, represented as (rounded to acre-feet), was computed by <br />taking the square root of the sum of the individual uncertainties squared, known as the quadratic sum. This <br />method and nomenclature is used throughout this report. This method was used because a simple sum does <br />not account for the partial cancellation of errors occurring when calculating the total uncertainty derived from <br />individual values that are random and independent of each other. The individual uncertainties were set as a <br />certain percent of the value. <br /> <br />· 'Water Use in New Mexico in 1985," New Mexico State Engineer Office Technical Report 46, <br />November 1986. <br /> <br />6 Communication with Peter DeswoodJ Executive Director, Division of Water Resources of the <br />Navajo Nation, January 31, 1985. <br />