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Reclaiming the Colorado River?

By Rod Parnell of Northern Arizona University The American Southwest faces water challenges, and few easy solutions are in sight. Demand for water is increasing rapidly: as the primary water resource in the Southwest, the Colorado River (see map) sustains seven U.S. states and Mexico, including major – and fast-growing – cities like Los Angeles,...

By Rod Parnell of Northern Arizona University

The American Southwest faces water challenges, and few easy solutions are in sight. Demand for water is increasing rapidly: as the primary water resource in the Southwest, the Colorado River (see map) sustains seven U.S. states and Mexico, including major – and fast-growing – cities like Los Angeles, Phoenix, and Las Vegas.

Supplies are dwindling, too. Climate change and drought, as well as increasing demand from population growth, have limited the Colorado River’s supply. And, as a December 2012 report from the Bureau of Reclamation recently pointed out, things aren’t getting better: the report predicts a 9-37% decrease in the river’s streamflow over the next 50 years.

In late 2012 water managers released a high volume of water from Glen Canyon Dam in Northern Arizona to replenish beaches along the Colorado River in the Grand Canyon. Photo: David Rankin, MyShot


The Neglected Three

Plans to manage this shrinking resource must realistically consider not just supply sources, but also demand sources and answer the questions, “How much water is there?” and “Who is entitled to what amounts?” Much of the current dialogue tends to focus on population growth. However, there are three other considerations that are critical in this context:

  • 1. Tribal rights

Federally-recognized Native American tribes have rights to a specific amount of water from the Colorado River. As adjudication continues to settle Native American claims, research is just beginning to establish how much water tribes in the Colorado River basin have historically used and what are they entitled to in the future.

  • 2. Mexico

Mexico has often received an insufficient amount of water from the Colorado River, and the quality of the water delivered to Mexico from the river is very poor. In a step toward ensuring that water flows to Mexico, the U.S. and Mexico recently signed a water-sharing agreement that allows Mexico to store water in Nevada’s Lake Mead.

  • 3. Natural ecosystems

In order to support aquatic and riparian life and habitats, the Colorado River needs to maintain a certain amount of water flowing in the river, called instream flow or eco-flow. Currently, much of the Colorado River’s uses divert water from the river, which has all but destroyed traditional  Colorado River delta ecosystems. Efforts to restore habitats along the lower Colorado River and in the Grand Canyon have to balance water delivery for conservation with that needed for power generation and consumption.

The best way forward?

Faced with such a complex situation, resource managers and planners have been grappling with solutions for years. With the Colorado River’s supplies shrinking, and alternative water sources running low, one potential game-changing solution remains: reclaimed water.

Reclaimed water is recycled from wastewater and generally used for irrigation, toilet water, and other non-potable uses. Reclaimed water is also used to recharge groundwater aquifer systems. Though using reclaimed water could help to mitigate the demands on the Colorado River, it is still far from certain that this is a risk-free approach. The health hazards of using reclaimed water are still very much unknown. Agencies at the local, state, and federal levels monitor 240 chemicals in water, but thousands of other man-made compounds are present.

Chemicals of Emerging Concern (CECs) such as pharmaceuticals, and personal care products like antifungals and deodorants may contribute to breeding antibiotic-resistant organisms that could pose problems for infections and other health considerations. Many traditional water treatment facilities do not effectively remove CECs, and these chemicals are, in fact, concentrated in reclaimed water. Until the concentrations of CECs in natural and reclaimed waters are better quantified, and their health and ecological effects are better understood, the widespread use of reclaimed water carries a level of risk.

Research needed immediately

As demand continues to exceed the supply of Colorado River water, and as researchers and policy makers continue to quantify the demands placed upon the river, reclaimed water has the potential to be one of the many solutions needed to solve the Southwest’s water supply issues. It is imperative, then, to forge ahead with further research in this area to determine which chemicals are present in reclaimed water, what their impacts might be, and whether—and how—associated health risks can be mitigated. Once we have that knowledge, then we can more fully understand how reclaimed water can become part of a sustainable solution to the Southwest’s water challenges.


Rod Parnell is a professor at Northern Arizona University in Flagstaff, in the School of Earth Sciences and Environmental Sustainability. The university has been researching and addressing Western environmental issues for nearly 50 years, and Dr. Parnell is an expert in western water and resource management. 

Editor’s Note: To learn more about the issues facing the Colorado River, and to get involved to make a difference, check out Change the Course, a partnership between National Geographic and other organizations.

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Meet the Author

Author Photo David Max Braun
More than forty years in U.S., UK, and South African media gives David Max Braun global perspective and experience across multiple storytelling platforms. His coverage of science, nature, politics, and technology has been published/broadcast by the BBC, CNN, NPR, AP, UPI, National Geographic, TechWeb, De Telegraaf, Travel World, and Argus South African Newspapers. He has published two books and won several journalism awards. In his 22-year career at National Geographic he was VP and editor in chief of National Geographic Digital Media, and the founding editor of the National Geographic Society blog, hosting a global discussion on issues resonating with the Society's mission and initiatives. He also directed the Society side of the Fulbright-National Geographic Digital Storytelling Fellowship, awarded to Americans seeking the opportunity to spend nine months abroad, engaging local communities and sharing stories from the field with a global audience. A regular expert on National Geographic Expeditions, David also lectures on storytelling for impact. He has 120,000 followers on social media: Facebook  Twitter  LinkedIn