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<br />C.16.9 <br /> <br />Changes in hydraulic head in the aquifer system and any resulting effects on the surface- <br />water system are a function of all stresses in the system. The magnitude and timing of these <br />changes at any point in the aquifer system are dependent on the hydraulic characteristics of the <br />aquifer, magnitude of the stresses, and the distance and direction (vertical as well as horizontal) <br />of the stresses from the point in the aquifer system. In order to interpret relations between <br />withdrawals by wells and resulting changes in hydraulic head, it is essential to have accurate <br />measurements of the magnitude and the three-dimensional location of all ground-water <br />withdrawals that could significantly affect hydraulic heads in the vicinity. <br /> <br />Major production wells are screened over large intervals of the aquifer. For example, the <br />distance between the top and bottom of the screened intervals in City of Albuquerque <br />production wells ranges from about 350 to 1,000 feet and averages about 700 feet (City of <br />Albuquerque IDes). The effect of withdrawals from these and similar wells on the aquifer and on <br />the surface-water system is therefore. dependent on the distribution of. withdrawal along the <br />length of each well's screen. Wells having large screened intervals generally do not draw equal <br />volumes of water along the entire well screen, and the primary contributing zones along the <br />screened interval may change with time. As an example, during a recent (1995) flow metering of <br />the Griegos 1 City production well, water was yielded only from the screened interval above the <br />depth of 640 feet (C.R. Thorn, written commun., April 4, 1995), although the screened interval of <br />the well extends from a depth of 232 to 802 feet below land surface. The most permeable zone in <br />the well's screened interval was originally (the well was drilled in 1955) the lower part, but <br />cementation over the years has clogged this zone. <br /> <br />InformatioJ'l on the volume of ground-water withdrawal from production wells (other <br />than private domestic wells) in the Albuquerque Basin is collected and recorded by the New <br />Mexico State Engineer Office. Maintaining the accuracy and completeness of these records is <br />essential for interpreting any observed changes in hydraulic heads in the aquifer system and any <br />resulting effects on the surface-water system, Withdrawal by large production wells (producing <br />more than about 100 acre-feet per year), such as those for the City of Albuquerque and other <br />major water users, potentially have the largest effects on the aquifer and surface-water system. <br />Accurate metering of withdrawals by these wells, and at a minimum, records of monthly <br />withdrawals is essential. It will also be useful to maintain daily records for these wells in areas <br />where continuous measurements of the vertical distribution of hydraulic heads are available so <br />that aquifer stress and response relations can be analyzed and aquifer characteristics in the <br />vicinity of particular wells can be estimated. Records of withdrawal for other production wells <br />are needed on at least an annual basis; however, if withdrawals from those wells fluctuate <br />significantly during the year, records maintained on a more frequent basis are needed to include <br />those fluctuations. Because of the large amount of withdrawal data that would be generated, <br />maintaining the data in a computerized data base is essential for practical application, <br /> <br />Although withdrawal information is readily obtainable, information on the vertical <br />distribution of withdrawal is not. This information is essential for wells screened over large <br />intervals, such as City of Albuquerque wells and other large production wells in the area. The <br />vertical distribution of withdrawal from the majority of wells having smaller screened intervals <br />can be estimated within reason using existing well-completion information. <br /> <br />Because of the large number of private domestic wells in the basin and the relatively small <br />volume of withdrawal from each well (3 acre-feet per year maximum), maintaining records for <br />each well is impractical. Withdrawals froin these wells can be estimated using the population in <br />areas not served by water systems and average per capita water use, or by the number of <br />domestic wells in an area and average household water use. Rural per capita water use in New <br />Mexico where outdoor watering is insignificant has been estimated to be about 64 gallons per <br />capita per day; however, where outdoor watering is common, 150 gallons per capita per day may <br />be more realistic (Wilson, 1992, p. 18, 96). Digital population data are available from the <br /> <br />23 <br />