Sometimes we hear people talk about sources of water as underground lakes or rivers. Many a child has envisioned a vast tunnel harboring a raging stream. If you're living in a karst area, perhaps. These are regions abounding in caves, and where indeed you may have a river or a small lake in the traditional sense. Elsewhere, though, the source is from wells intersecting the water table.
Sediments such as gravel or sand have lots of room for water between
the particles that make them up. These water-bearing strata commonly are known as
aquifers. An underground river, then, is apt to be water flowing slowly through the
permeable layers. These layers sometimes were laid down ages ago as the bed of a
surface river. Wells drilled close to the Rio Grande may be recharged by water from the
river itself seeping into intercepted aquifers. Unfortunately, much of the well water
used by large cities in the Chihuahuan Desert comes from sediments that have received
little or no water since the ice ages—unsustainable water deposits to be mined
until they run out.
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.