oast Guard, Coconino County Health, Drug-testing, the Prospectus... a deluge of issues for GCRG, but at least we don’t have to worry about Canyon Forest Village. That’s Tusayan’s problem, right? And maybe it’ll turn out to be a nice place for some Park employees, take a little pressure off South Rim. Oh, and they might need a little water out of the Redwall-Muav aquifer.

Now, that may be our problem.

The circulation of natural waters ties together diverse terranes. In the Grand Canyon region, the carving of the canyon released groundwater from the Redwall, Temple Butte, and Muav Limestones, to flow as springs where faults intersect the face of the canyon. Now water under the Tusayan area rushes from Grapevine, Indian Garden, Cottonwood, Hermit, Boucher, Havasu and many other springs along the south wall of the Canyon.
In an August 1995 editorial, Grand Canyon National Park Superintendent Rob Arnberger recognized this link and the potential impacts of pumping groundwater from wells that tap the limestones. His concern was “that these wells are being developed without consideration for the impact they may have on springs in the Grand Canyon—and, by extension, without consideration for the flora and fauna these water resources support.”
To understand how springs of Grand Canyon might be effected by pumping a well for Canyon Forest Village, we need to look at groundwater storage in the rocks, at faults, fractures, and cave systems that siphon groundwater from one area to another, and at variations in springflows. Rock formations that hold significant amounts of groundwater are called aquifers. Think of them as stiff sponges rather than lakes. Good aquifers are large and have lots of openings which are well connected. The underlying formations block the downward movement of water.
The Redwall-Muav aquifer is thick and regionally continuous, but its boundaries are somewhat uncertain. The aquifer is thought to be bounded by the Toroweap fault to the west, by the Grand Canyon to the north, and by groundwater basin divides that mark where groundwater drains east into Blue Springs and south into the Verde River area. The underlying Bright Angel shale is a fine aquitard—its clays retard the downward flow of water.
The limestones are fractured and dissolved into large openings—remember all those caves and tunnels in Marble Canyon. The calcium carbonate of limestone dissolves easily in the weak acid formed by carbon dioxide and water. Stress fractures in the limestone are widened into conduits by the solution process. Recalling Marble Canyon’s natural geologic cross section, the openings and fractures in the Redwall form a good network for transmitting water. In short the Redwall-Muav aquifer is a regular aqueous bonanza.
But wait. What about the springs? The springs are fed by the regional aquifer, or smaller isolated (perched) aquifers, or by local rainfall stored in gravels. And when a well is drilled? A pumping well creates a cone of depression in the water table. The inverted cone expands outward as pumping continues.

At Grand Canyon the cone shape is complicated by the variation in rock types above the Redwall and by the fracture flow system in the limestones. At the worst, a spring can lose all its flow if the spring and well share the same fractured flow zone, or if the drawdown cone intercepts flow toward the spring (see the drawing). Otherwise, a new dynamic equilibrium will be established between springflow, pumping rate, other outflow, and inflow to the aquifer.
Several studies are gathering or modeling data relating to the proposed development. Canyon Forest Village hired Errol L. Montgomery and Associates, Inc. The National Park Service and the U.S. Geological Survey are cooperating on a springflow monitoring project in the park. Researchers from the University of Nevada, Las Vegas are sampling springs for chemical signatures. Several deep wells, including one at Valle and one at Havasu, can give us information as well.
Everything that follows is preliminary. Montgomery and Associates modeled 0.1% to 9% decreases in flows from Hermit, Indian Garden and Havasu, based on a bunch of assumptions. The folks at UNLV are beginning to think the spring water they sampled is at least older than the days of atomic weapons testing, possibly much older. This is based on some esoteric analyses of fancy chemical isotopes. The folks at the USGS and the Park Service notice a lot of variability in springflow data. (I have all this from reliable third-hand sources.)
Although spring discharges have been measured over many decades, these measurements have not been part of a consistent established program. We may not have enough information. Pre-bomb groundwater ages suggest the springs may be issuing water that would be slow to replenish if mined by wells. Also, since springflows may not be in direct equilibrium with recharge of the aquifer, we need to be cautious with projections.
Before we can get any closer to real answers about the character of the Redwall-Muav aquifer, Canyon Forest Village needs to make some real decisions about how big they will become. The proposed land exchange calls for careful planning that acknowledges the undeniable connection between adjacent plateau lands and Grand Canyon National Park.
An active approach on one front of this issue would be to encourage the park to pursue Wild and Scenic designation for tributary streams, many of which are spring-fed. Designation requires study of the ecosystems surrounding the springs and the establishment of minimum flows. Grand Canyon National Park recently included Wild and Scenic designation in management objectives of the final General Management Plan.
On another front, I join Rob Arnberger in the hope that landowners and researchers come together to protect our precious springs.

Stay tuned, there’s an EIS in progress.

Kelly Burke