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<br />lc.r..~ ;) <br />C v-v <br /> <br />Elastic specific storage (sum of the elastic specific storage components) is generally about <br />10-6 per foot of aquifer thickness (Lohman, 1979, p. 8). By measuring changes in aquifer <br />thickness in an extensometer and hydraulic heads in piezometers during an aquifer test in the <br />Albuquerque area, C. E. Heywood (Hydrologist, U.s. Geological Survey, written commun., May <br />1995) calculated the average elastic specific storage over ,the 1,000-foot depth of the extensometer <br />to be 2 x 10-6 per foot. Although, other calculated values of elastic specific storage are not <br />available for the Albuquerque Basin, this is consistent with values calculated for other basin-fill <br />aquifers summarized by Haneberg (1995b, p. 63-64). Kernodle and others (1995) used an elastic <br />specific-storage value of 1 x 10-6 per foot in the initial simulations using their ground-water-flow <br />model. However, it was adjusted to 2 x Hj-6 per foot to obtain better matches between simulated <br />and measured hydraulic heads. . <br /> <br />The inelastic specific storage component of aquifer compressibility (which would result in <br />a one-time release of water from storage) is commonly one to two orders of magnitude larger <br />than the elastic specific storage (Haneberg, 1995b, p. 63). Haneberg (1995b) calculated the <br />inelastic specific storage component to be about 6 x 10-5 to 2 x 10-4 per foot based on porosity <br />logs from 5 wells in the Albuquerque area. <br /> <br />Monitoring the aquifer in the Albuquerque area for elastic and inelastic compaction is <br />essential to more fully understand aquifer storage characteristics, and thus, to understand <br />aquifer/surface-water system interaction. The USGS, in cooperation with the City of <br />Albuquerque, has established a geodetic network and installed an extenso meter to detect aquifer <br />compaction. <br /> <br />Flow Characteristics of System Components <br /> <br />Components of the flow system considered in this section are those that recharge water to <br />or discharge water from the aquifer system, and flow within the aquifer system itself. The <br />recharge and discharge components include ground-water withdrawal; Rio Grande, canal, and <br />drain seepage; basin margin and tributary recharge; riparian and wetland evapotranspiration; <br />irrigation seepage; and septic-field seepage. These system components are discussed in <br />decreasing order of relative volumes of water in the ground-water budget for the Albuquerque <br />area as calculated from the Kernodle and others (1995) ground-water-flow model. <br /> <br />Ground-Water Withdrawal <br /> <br />Ground-water withdrawal in the Albuquerque area was estimated by Kernodle and others <br />(1995) to be about 157,000 acre-feet for the year ending in March 1994, Ground-water <br />withdrawal by wells is a human-induced stress on the ground-water / surface-water system. The <br />water withdrawn by wells initially comes from storage within the aquifer. The withdrawal of <br />water creates a cone of depression in the potentiometric surface near the well, creating a <br />hydraulic gradient toward the well. The cone of depression spreads, as shown by changes in <br />hydraulic head as it propagates through the aquifer. When the cone of depression comes in <br />contact with a ground-water/surface-water interface, the withdrawal will have an effect on the <br />movement of water between the aquifer and the surface-water system. The effect can be either an <br />increase in the volume of water moving from the surface-water system to the aquifer or a <br />decrease in the volume of water moving from the aquifer to the surface-water system. In either <br />case, the result is a reduction of the volume of water in the surface-water system. Each <br />additional withdrawal creates an additional effect. <br /> <br />22 <br />