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Sunday, November 30, 2008

Brackish Water Can't Sustain N.M.

By Bruce Thomson
UNM Water Resources Program
          New Mexico's water is severely over-allocated. State water managers are trying to squeeze out every last drop to meet delivery obligations to our neighbors while ensuring adequate supply to our own residents.
        Yet our state continues to grow. Population between Albuquerque and Santa Fe is projected to grow by almost 50 percent by 2040. New golf courses appear with regularity along the middle Rio Grande corridor. And the State Engineer issues roughly 7,000 new permits every year for private wells and associated water rights.
        At the same time we see increased water demand, the water industry has achieved remarkable advances in treatment technologies, including desalination, that offer better performance and lower cost. In response, many communities and developers in New Mexico are considering saline or brackish ground water as a source of supply.
        The interest in deep brackish water is heightened because under current law the Office of State Engineer does not have jurisdiction over non-potable water in aquifers deeper than 2,500 feet. As a result, some water managers and developers consider deep brackish water to be "new" water; water that the state does not control and is of uncertain ownership.
        But before we develop this resource, New Mexico residents need to understand a little bit about it and the consequences of its development.
        Most importantly, we must recognize that, with few exceptions, deep brackish ground water supplies are not sustainable. These aquifers usually contain water trapped by geologic events that occurred hundreds of thousands or millions of years ago. They receive little or no recharge from surface sources, such as infiltration from rainfall or percolation from streams.
        It was recently estimated that the deep brackish ground water resources in Sandoval county will support a population of 300,000 for 100 years. What happens then? Do proponents of this development think that the demand for water elsewhere in the state will have decreased so that other water sources will be available? That the cities of Albuquerque, Santa Fe and Rio Rancho won't have also grown? That irrigated agriculture will no longer need river water for crops? Or perhaps that scientists and engineers will develop magic technologies to create water from nothing using only renewable energy sources?
        One hundred years is a long time, but because there is no alternative, I believe that a 100-year planning horizon is too short for any residential development. For these projects we must require sustainability. We must assure that water is available for future generations. Forever.
        Though we cannot depend on deep brackish sources as our sole source of supply, we should recognize that they are in fact a valuable resource and can play an important role in the growth of our communities. Their most obvious value is as a source of water during periods of drought. In this scenario, deep brackish sources would provide water during dry years and be replenished during wet years.A second use might be as a source of minerals such as gypsum for wallboard, salt for industrial or food applications, or trace minerals such as uranium or vanadium for energy or material uses. Brackish water would be pumped to the surface, the minerals recovered, and the water returned to the aquifer. In both strategies the water resource is preserved, not consumed.
        Where do we go from here? First, we need to establish a dialogue that includes water managers, the development community, water scientists and engineers, and the public regarding the management of these resources.
        More immediately, the Legislature needs to give the state engineer authority over all water resources in the state, including deep brackish ground waters. Responsible planning cannot proceed without it. Furthermore, under the current situation nobody knows who owns the deep brackish water — the land owner? the owner of the mineral rights? the first person to tap into it?
        Next, we must insist that water dependent development in New Mexico be sustainable. We may allow communities to tap into non-sustainable supplies for short periods, but ultimately, every residential development must include a credible plan describing how it will provide water forever.
        Finally, we must recognize that it's not "new" water, it's old water. Very old.
        Bruce M. Thomson is director of the Water Resources Program at the University of New Mexico, where he is regents professor of civil engineering. (bthomson@unm.edu)