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<br />. (llC')') <br />()\..' u.J'- <br /> <br />The Middle Rio Grande Conservancy District (MRGCD, the agency that operates and <br />maintains the irrigation system, including diversions, canals, and drains) measures canal and <br />drain flow with continuous recording gages at four locations between Angostura and Isleta <br />Pueblo and is proposing several more (Ray Gomez, Middle Rio Grande Conservancy District, <br />written commun., September 22, 1995). The riverside drain and the diversion into the <br />Albuquerque Main Canal are monitored just downstream from the diversion at Angostura. The <br />Corrales Main Canal is monitored downstream from the siphon (fig. 3A), and the Albuquerque <br />Riverside Drain is monitored downstream from its confluence with the Alameda Drain (fig. 3B). <br />Additional continuous recording stations are proposed for the canal and drain system returns to <br />the Rio Grande. This would allow separation of gains or losses in the drain and canal systems <br />from those in the river channel. <br /> <br />Basin-Margin and Tributary Recharge <br /> <br />The aquifer system at the margins of the Albuquerque Basin is recharged by inflow of <br />ground water from adjacent basins and by mountain-front recharge. Ground-water inflow from <br />adjacent basins, such as the Espanola or San Juan Basins (fig. 2), occurs at depth in the aquifer <br />system. Mountain-front recharge enters the aquifer system at the contact of basin-fill deposits <br />and adjacent mountain blocks, such as the Sandia Mountains east of Albuquerque, Mountain- <br />front recharge occurs as infiltration of water from streams draining the mountains and as <br />seepage of shallow ground water from mountain valleys or near-surface fractured rock of the <br />mountain block. <br /> <br />Tributary recharge originates as infiltration of water from streams and arroyos that flow <br />toward the Rio Grande from the basin margins. Most tributary recharge is from unlined <br />channels that contain flow for significant time periods. Ephemeral arroyos probably contribute <br />little recharge in comparison because they flow for only short periods as a result of large <br />thunderstorms. Much of the water infiltrated into the arroyo channels during these periods is <br />subsequently evapotranspired to the atmosphere, leaving little water to percolate to the water <br />table (Thomas, 1995, p. 21). <br /> <br />In the Albuquerque area, basin-margin recharge is from the Sandia and Manzanita <br />Mountains, and tributary recharge is along Tijeras Arroyo. Ground-water inflow into the <br />Albuquerque area comes from other parts of the Albuquerque Basin, as discussed previously <br />(see "Santa Fe Group aquifer system" section), rather than from basins adjacent to the <br />Albuquerque Basin. Basin-margin and tributary recharge cannot be directly measured and <br />therefore must be estimated. Basin margin and tributary recharge in the Albuquerque area was <br />estimated using the Kernodle and others (1995) model to be about 25,000 acre-feet for the year <br />ending in March 1994. The ground-water-flow model (Kernodle and others, 1995, figs. 36C and <br />37 A) shows that simulated change in aquifer storage in the basin was sensitive to simulated <br />change in mountain-front and tributary recharge, as well as simulated change in ground-water <br />withdrawal. Because changes in stresses to the aquifer system primarily result in either a <br />change in aquifer storage or a change in the rate of water movement between the surface-water <br />system and the aquifer system, the ability to reasonably estimate recharge would be useful in <br />order to better understand hydrologic relations between the surface-water and ground-water <br />systems. <br /> <br />26 <br />