The desert water problems are not so much that there's little underground water as that much of that water is so loaded with minerals as to be unusable. Ground water originates as precipitation that percolates into the bolsón fill. During this process, rain and snow water dissolve salts and other substances from rock and soil. The dissolution tends to continue underground until the water is saturated. The salt-laden water, being heavier because of its load of minerals, slowly sinks deeper, while fresher water floats on top.
It is this layer of fresher water, mostly left over from the Ice Age,
that we're mining and that we're rapidly depleting. To stretch out the supply,
we can dilute saltier water by mixing it with fresher waters. A different approach,
taken by El Paso, is to re-inject some used water back into the aquifer after
treatment. A third strategy, now being implemented, is desalinization—removal of
the salts. There are two major drawbacks, though: it's relatively expensive, and it
produces a hard-to-get-rid-of byproduct. Namely, lots and lots of salt.
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.