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<br />C016:;~) <br /> <br />capita per day and noted that this is consistent with other studies from other parts of the country. <br />The smaller number is probably more reasonable for the volume of water reaching leach fields. <br />However, if vegetation is growing over a leach field, some of the water will be evapotranspired <br />by the vegetation. <br /> <br />Information is available to estimate evapotranspiration from leach fields. Consumptive <br />use by various types of vegetation was reported by Blaney and others (1938) and the Bureau of <br />Reclamation (1994a, 1973a, b). Information needed to determine the distribution of septic-field <br />seepage includes digital population data, available from the U.S. Bureau of Census (1970, 1980; <br />1990), and average number of persons per household by area, reported by the U.S. Department <br />of Commerce (1991). Information on leach-field sizes can be obtained from information <br />required by the State and counties for permits. Bernalillo County, which includes most of the <br />Albuquerque area, maintains a digital data base containing this information, Although the data <br />base is estimated to contain data for only about one-third of the estimated 20,000 septic tanks in <br />the county (City of Albuquerque and Bernalillo County, 1992, p. 25), it can provide an.estimate of <br />average septic-field size in the area. . <br /> <br />Because of the relatively small volume of water septic-field seepage contributes to the <br />estimated water budget of the area, estimates can be improved using only information that is <br />currently available. Additional data collection or field experiments would not be cost efficient <br />based on the additional understanding of ground-water/surface-water interaction that would <br />be provided. <br /> <br />Summary of Information Needs <br /> <br />The previous two sections describing components of the Rio Grande and the Santa Fe <br />Group aquifer system discussed essential additional information and useful additional <br />information needed to improve quantification of hydrologic relations between the surface- and <br />ground-water systems. Essential information is considered necessary to improve the <br />quantification of the system. Useful information, although not necessary to improve the <br />quantification of the system, would add additional understanding of the system. The essential <br />and useful activities and information identified in the previous sections are summarized below. <br /> <br />Essential Activities and Information <br /> <br />Install additional observation wells <br /> <br />Measure the vertical distribution of hydraulic heads in the aquifer system and maintain a <br />computerized data base of the measurements <br /> <br />Measure volume and three-dimensional location of ground-water withdrawals, and <br />maintain a computerized data base of the measurements <br /> <br />Measure flow of the Rio Grande, canals, and drains at sections near river gages and maintain <br />a computerized data base of the measurements' <br /> <br />Document changes in the volume of water in aquifer storage <br /> <br />Monitor elastic and inelastic compaction <br /> <br />Estimate riverbed hydraulic conductivity <br /> <br />Define canal dimensions, bottom elevations, operating stage, percentage of time containing <br />water, and location of lined or unlined segments <br /> <br />Define drain dimensions and bottom elevations (if water table is below bottom and if used <br />. for water conveyance) <br /> <br />29 <br />