Study: Colorado River Water Supply Slowly Falling Short of Users

Anne Minard
December 14, 2012


The Colorado River – which is the lifeblood to 40 million people and no less than 22 tribes – stands to fall at least 3.2 million acre-feet short of its users’ needs by 2060. And even the most ambitious water-saving strategies won’t fully ease the strain.

That’s the main finding of a comprehensive, years-long effort called the Colorado River Basin Water Supply and Demand Study, led by the Bureau of Reclamation and the seven Colorado River Basin states, and unveiled Wednesday, December 12 by Interior Secretary Ken Salazar. Myriad stakeholders, including tribes, agricultural users, municipal and industrial water brokers, power users, and conservation and recreation groups contributed to the study partly by assessing their water needs into the future. Those collective water needs were rolled into various futuristic scenarios of climate change and population growth, and compared with several comprehensive proposals about ways to ease demands on the already stressed Colorado River system.

“There’s no silver bullet to solve the imbalance between the demand for water and the supply in the Colorado River Basin over the next 50 years – rather, it’s going to take diligent planning and collaboration from all stakeholders,” said Salazar, in a press release about the study’s findings. “Water is the lifeblood of our communities, and this study provides a solid platform to explore actions we can take toward a sustainable water future.”

Water rights along the Colorado are generally complex, carrying a mix of seniority dates and access issues. Tribal rights to the Colorado are arguably even more intricate, because not all tribes in the watershed have gone through the legal process of turning aboriginal claims into actual water rights. In all, 13 tribes still have unresolved Colorado River Basin claims including the Navajo Nation, Ute Indian Tribe of the Uintah and Ouray Reservation, Ute Mountain Ute Tribe, Havasupai Tribe, Hopi Tribe, Hualapai Tribe, Kaibab Band of Paiute Indians, Pascua Yaqui Tribe, San Carlos Apache Tribe, San Juan Southern Paiute Tribe, Tohono O’odham Nation, Tonto Apache Tribe and the Yavapai Apache Nation.

Tribes participated in the study both directly and through representatives with two groups: the Ten Tribes’ Partnership, which is a branch of the Colorado River Water Users’ Association, and the non-profit Inter Tribal Council of Arizona.

George Arthur, Navajo, is chairman of the Ten Tribes’ Partnership and president of the Colorado River Water Users Association. In an e-mailed statement, Arthur said the partnership and its members appreciate the Bureau of Reclamation and others who made a significant effort to work with tribes.

“The Study has brought to surface the need for additional studies to better understand the water allocated to tribes and the need for resolution of claims,” he added. “Reclamation has committed to work with the tribes on potential future studies and dialogue has begun to identify funding mechanisms.”

John Lewis is a member of the Colorado River Indian Tribes and executive director of the Inter Tribal Council of Arizona. He pointed out that this latest study joins a long line of attempts to get a handle on supply and demand issues in the Colorado River.

“The projected shortage seems to go up with each study,” he said. “That’s how critical this is for the West, and particularly the Southwest.”

The study’s signature finding is that the average imbalance in future supply and demand is projected to be greater than 3.2 million acre-feet by 2060; one acre-foot of water is roughly the amount of water used by an average household in a year. The report predicts that demand for Colorado River water will reach 18.1 million acre-feet if population grows to a projected 49 million people by the year 2060. That’s the slow growth scenario; the basin supports a population now of about 40 million people. In a rapid population growth scenario – an increase to 77 million people – demand would rise to about 20.4 million acre-feet. Either way, the numbers don’t work. Historically, about 15 million acre-feet flowed through the Colorado River. After more than a decade of drought, the basin has been hosting just 12 million acre-feet of water a year.

The report delves into ample detail about what the disparities could mean for the region.

No matter what, according to the study, some water uses will take hits in the coming decades. Colorado River flows generally, for example, are projected to fall below ecologically advisable levels about a third of the time, no matter what conservation strategies are employed. Between 14 and 42 percent of the time – depending on which water-saving strategies get implemented – water in Lake Mead is likely to dip below levels that sustain effective power generation at Hoover Dam; between 30 and 57 percent of the time, Lake Mead levels will be too low to sustain shoreline recreational facilities. Water deliveries to the Upper Basin – which includes Colorado, New Mexico, Utah and Wyoming – will be compromised between 2 and 7 percent of the time. Water deliveries to the Lower Basin states – Nevada, Arizona and California – will be compromised between 3 and 19 percent of the time.

All of the predictions consider supply and demand variables like projected climate change and population growth.

According to one climate change scenario, for example, the Colorado’s flow at Lees Ferry – where the Colorado enters Grand Canyon National Park – is projected to decrease by about 9 percent over the next 50 years.

“Droughts lasting 5 or more years are projected to occur 50 percent of the time over the next 50 years,” the report says of that scenario. “Projected changes in climate and hydrologic processes include continued warming across the Basin, a trend towards drying … increased evapotranspiration and decreased snowpack as a higher percentage of precipitation falls as rain rather than snow and warmer temperatures cause earlier melt.”

The predictions also assume varying combinations of conservation strategies will be put into place. The most dire numbers assume that nothing is done. The most optimistic numbers assume we develop and employ sophisticated techniques like desalination, the reuse of wastewater, watershed management, water importation and assorted conservation methods.

So far, even in drought years, most Colorado River water users have dodged the shortage bullet:

“Because of the Colorado River system’s ability to store approximately 60 million acre feet, or nearly 4 years of average natural flow of the river, all requested deliveries were met in the Lower Basin despite recently experiencing the worst 11-year drought in the last century,” the study reports. “However, there have been periodic shortages throughout the Upper Basin and the adjacent areas of the Basin States that receive Colorado River water.”

But as demand continues to increase – and climate factors squeeze supply – that’s not guaranteed to continue. That puts many water users at risk, including tribes in some cases.

“Some tribes do have senior rights,” Lewis said. “Still, given the disparities in supply and demand, it could be of concern. Even with something like the CAP [Central Arizona Project], where again tribes have some secure rights, the position of Arizona still is lower for the canal water than some of the other states.”

The tribes most at risk are those whose rights haven’t been quantified, Lewis added. “Arizona, California, Nevada – these are all fast-growing states. That puts pressure on how best to meet the water rights. Water is reserved for settlement use, but it’s not going to be enough.”

But Lewis added that through his participation in the Colorado River Basin Water Supply and Demand Study, he’s developed confidence that those issues are exactly where the Bureau of Reclamation will be focusing next.

“We need to get serious and start engaging tribes on a tribe-by-tribe basis,” he said. The Bureau has committed in the report to do that.”


Submitted by Teri Baker on

colorado river is experiencing a shortage of water and tribes are suffering and it is going to get worse.

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