New Mexico Geological Society Annual Spring Meeting — Abstracts

Many river-connected ground-water basins store large volumes of water that can’t be pumped and used because the resulting depletion of the flow of the river would impair the rights of downstream users. The Albuquerque-Belen Basin, for example, stores several hundred million acre-feet, which might be compared with the recent (Year 2000) combined consumptive use of 184,000 acre-feet in Sandoval, Bernalillo and Valencia Counties, but the Rio Grande is already over-appropriated, and an increase in pumping would cause still more depletion of the stream. The Española and Lower Rio Grande Basins store hundreds of millions of acre-feet more. If the system is too large for channel-lining to be practical, to isolate the river from the ground-water system, the stored ground water must simply remain in place.

Another approach would be to pump the non-renewable ground water, put to beneficial use only the portion that actually comes from storage, and return the balance to the stream. As the cones of depression expand and eventually reach equilibrium, the entire amount pumped would be at the expense of streamflow—but pumping and delivery to the stream must continue forever so as to prevent the natural system from replacing the volume withdrawn from storage. Although it seems implausible, this situation is theoretically sustainable if the revenue derived from sale of the stored water has established a perpetual fund to support the continued pumping. One hypothetical system in the Rio Grande valley could provide a total of about 6.8 million acrefeet for municipal use (with 50-percent return flow) over 100 years, at a cost less than large-scale desalination. A very reliable understanding of the ground-water regime, and the threshold of subsidence problems due to excessive drawdown, would be vital. Public-policy implications include allowing growth to become dependent on a continually shrinking supply, responsibility for the perpetual pumping, and commitment of future energy resources.