Highlight 15--Finding Water for Thirsty Southwestern Cities
The explosive growth in urban areas of the arid Southwest has placed exceptional demands on limited ground-water resources. Interdisciplinary GD studies in several Southwestern U.S. cities, conducted in cooperation with the WRD, State and local governments, and universities, have used geologic mapping, geophysical imaging, and geochemical studies to better understand geological limitations on the quantity and quality of municipal ground-water supplies. For example, near Albuquerque, NM, detailed geologic mapping, coupled with high-resolution airborne geophysical surveys, has been used to identify the location and geometry of buried, intrabasin faults that offset the principal gravel aquifer units within the Middle Rio Grande Basin (fig. 15). In addition, GD geochemical studies of drill core samples and ground waters have helped track the origin and pathways of naturally elevated arsenic concentrations in some of the municipal water-supply wells. Knowing that aquifers supplying the city with potable water are more limited than originally thought, local governments can plan more realistically for urban growth. Similar USGS projects in Flagstaff, AZ, and Las Vegas, NV, have helped identify important basins or geologic structures that may host ground water or affect its flow.
Figure 15. Buried intrabasinal faults that limit the extent of the aquifer units in the Middle Rio Grande Basin near Albuquerque, NM. Magnetic data collected by high-resolution airborne geophysical surveys were used to identify the location and geometry of the faults. 1 nanotesla=1 gamma, a measurement of magnetic field strength. From Grauch and Millegan (1998).
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Last updated 04.08.98