Nelson: Understand groundwater
By steve nelson
I'd like to offer some perspective on the Nov. 13 Tribune article "Utah governor weighing options to Snake Valley water standoff."
We've conducted research on the Spring Valley and Snake Valley groundwater system and recently published our findings in Hydrogeology Journal, an international academic publication.
Should Utah sign an agreement with Nevada on exportation of water to Las Vegas?
Before any pact is entered, it is in the best interest of Utah that the way groundwater moves is understood by the parties involved and affected.
The traditional view, the so-called interbasin flow model, maintains that the fractured limestones that make up much of the bedrock beneath the desert mountains and valleys of western Utah and eastern Nevada allow water to flow quite freely. In other words, water can flow beneath multiple valleys, and the mountains that separate them, as long as there is limestone to flow through.
The interbasin flow model views limestone as one enormous aquifer. This view has two implications for Utah. First, water beneath Spring Valley, Nevada, should flow into Snake Valley, Utah; thus, water development in Nevada can impact water availability in Utah.
Second, water development in such a large aquifer is like sucking water through little straws from a very large cup. You can "drink" for a long time.
Although the technical details are beyond the scope of an op-ed piece, our research strongly suggests that the interbasin flow model is largely wrong. Each basin behaves more-or-less independently. Water development is more like sucking water through straws from many small cups.
Even a 2011 report by U.S. Geological Survey scientists generally supports our view, although this federal agency has been a chief proponent of interbasin flow for decades.
The water beneath Snake Valley is, in many areas, much older than the water in Spring Valley. Whenever groundwater is extracted faster than it is replenished, it is being mined. Exploiting older water only worsens impacts of groundwater mining as the natural system replenishes it only very slowly.
Although some development in Spring Valley, Nevada, might be sustainable and have little impact on Utah, large-scale water development in Snake Valley could rapidly deplete groundwater resources. Although Snake Valley is largely in Utah, the Southern Nevada Water Authority (SNWA) has had its eyes on Snake Valley. Due to the antiquity of its water, large-scale development from Snake Valley should be vigorously resisted.
Our work also suggests that monitoring declining spring flows and water levels in wells as a safeguard against excessive development is fundamentally flawed. If it takes decades of pumping for spring flows to decline, it will take centuries for those flows to recover on their own once pumping stops even if the climate does not change. And really, who believes the pumping will stop once started?
Depending on your point of view, our research offers both good and bad news for water resources in Snake Valley. Given my environmentalist bent, part of me wishes that the development of water in Spring Valley would clearly and immediately impact Utah, providing direct leverage to put a stop to the whole boondoggle.
However, that is not my chief concern at this moment, which is that the whole SNWA proposal may be based on a faulty view of how groundwater moves in this part of the world.
The impacts of water development cannot be anticipated until the way in which water moves, how much of it there is, and how long it has been in the ground are understood.
Until that day, Gov. Gary Herbert should not sign anything.
Steve Nelson is a professor of geochemistry at Brigham Young University.
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