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Colorado River Faces Flood and Drought--Becoming Less Reliable?

The river provides water for the western U.S. but faces significant challenges under climate change



Wolfpack306/Wikimedia Commons

The Colorado River has a long journey. It flows from mountains, runs by cities, winds through remote, rust-colored canyons and touches seven states before entering Mexico. It's a natural wonder, but also a life source of the more than 30 million people who rely on it.

But in recent years, the Colorado River has become less reliable. Since 1999, abnormally low precipitation totals and hot and dry conditions have brought reservoir water levels close to record lows. The multiyear drought, the most severe since documentation began more than 100 years ago, has put the water supply in the thirsty Southwest in jeopardy.

This year, heavy snowpack and spring precipitation have brought the region some relief by partially refilling the reservoirs. But while National Oceanic and Atmospheric Administration research shows that snowmelt runoff into the upper basin hasn't been this high since 1986, the southern end of the Colorado River continues to stop shy of the Sea of Cortez, where it used to run until the late 1990s.

The paradox is that this season stands in such stark contrast to the past 11 years of drought, highlighting the types of variability that climate change can wreak on the hydrological cycle.

"It's not at all uncommon for the basin to have high runoff years in a longer period of drought," said Pamela Adams, outreach coordinator with the Bureau of Reclamation, the body that manages the Colorado River Basin. "We can see that in both the past 100 years of data, plus you can see it in the tree-ring data."

The Bureau of Reclamation released the first of three interim reports last month as part of its broader Colorado River Basin Water Supply and Demand Study. The report is designed to provide an outlook on the next "highly uncertain" 50 years (until 2060) of the river's life. Authors wrote that in the nearly quarter-million-square-mile Colorado River Basin, "climate change, record drought, population increases and environmental needs" are likely to make water supplies ever scarcer.

One scenario already found that the mean natural flow at Lees Ferry, Ariz., is projected to decrease by 9 percent over the next 50 years and experience an increased frequency and duration of drought.

Understanding the supplies, demands and risks
The Colorado River is vital to all of the seven states touching the basin -- Arizona, California, Colorado, New Mexico, Nevada, Utah and Wyoming. Apart from providing water for municipal use, the river irrigates 4 million acres of land and sustains 15 Native American tribes, seven National Wildlife Refuges and 11 National Parks, according to the basin study. Hydropower stations along the Colorado River supply more than 4,200 megawatts of generating capacity.

It is also a significant resource for Mexico, because the United States is legally required to ensure its southern neighbor receives 1.5 million acre-feet -- the unit used to measure water resources -- of water annually.

"What this is trying to do is help us think about the possible ways the future will evolve along the Colorado River," said Adams of the Colorado Basin report. "We're looking at scenarios and get a range of possible futures and understand a range of supply and demand so we get a range of what the balances may be."

Previous environmental impact statements have been focused on managing supply, said Adams. This new report, scheduled for completion by July 2012, will for the first time focus on understanding demand because of the effects of climate change. The study is based on data from historically observed and paleo-reconstructed water flow records, as well as projections from global climate models.

"Concerns regarding the reliability of the Colorado River system to meet the future needs of Basin resources in the 21st-century are heightened, given the likelihood of increasing demand for water throughout the Basin, coupled with projections of reduced supply due to climate change," wrote the authors of the report.

The risk assessment is integrated with the SECURE Water Act, legislation passed in 2009, in which Congress determined there should be a full-scale report on the Colorado's water supply.

According to the first report under the SECURE Water Act, "As the effects of climate change and snowpack are realized throughout the Colorado River Basin, these effects will drive changes in the availability of natural water supplies."

Earlier independent research also shows that with climate variability, risks to the precious Colorado water resources increase.

"Virtually all the climate models suggest there will be a reduction of inflows in the river. It could be 10 to 30 percent," said Tim Barnett of the Scripps Institution of Oceanography, who published a report on the Colorado River in 2009. "It's not a problem you can cavalierly say, 'We will worry about this in 20 to 30 years.'"

The year of a little relief
Lake Powell, largely in Utah, and Lake Mead, along the Nevada-Arizona border, account for approximately 85 percent of the Colorado River's water storage capacity. Wet years come as a huge relief to the reservoir managers, but when the lakes get low, tensions start to run high.

"We had such a large hole in that reservoir, such a large amount of available capacity, that the water has been very welcome," said Richard Clayton, who operates Lake Powell for the Bureau of Reclamation.

"It's been a banner year for us at Lake Powell. We're going to see over 50 feet of filling from the low point, and year over year, we're going to see a net gain of 20 feet," said Clayton. "It doesn't seem like much, but it is. It's great for recreation, power supply; there are a lot of smiles because of how wet this year has been."

There are only two years -- 1983 and 1984 -- that have had more unregulated inflow than in 2011. This stands in stark contrast to less than a decade ago, when in 2002, the flow was as low as it has ever been in the history of Lake Powell, beginning in 1963.

The spring runoff has been so great it has even overwhelmed some northern areas of the basin, where authorities are still trying to assess the damages caused by flows that were 160 percent higher than average. In some places, the water caused lowland flooding and bank erosion and lapped up against the underbellies of bridges, restricting access to roadways, said Aldis Strautins of the Grand Junction Weather Forecast Office in western Colorado. Over July, the water levels have steadily receded.

Farther downstream, Lake Mead is also experiencing high water flows and levels. However, the reservoir will still be only 57 percent full by December 2011. This will take it 50 feet higher than last year, when the lake was at an elevation of only 1,083.8 feet -- had it dropped to 1,075 feet, it would have triggered a shortage declaration and forced Nevada and Arizona to curtail their use of the Colorado River.

Still struggling to reach the Sea of Cortez
To curtail the drain on the Colorado River, there have been some improvements in consumption practices. The Southern Nevada Water Authority, for instance, created a Water Smart Landscapes Rebate, which has helped convert 150 million square feet of lawn in the Las Vegas Valley into water-efficient landscaping. The project has saved the area billions of gallons of water.

Conservation efforts have also led to overall savings. According to a report by the Pacific Institute released in June, 28 water agencies in five separate states delivered less water in 2008 than they did in 1990, despite population and industry growth.

But continued population increases, coupled with the drains of development, farming and recreation, plus the impacts of climate change, have meant that more conservation needs to take place while there's still time to do it.

Protect the Flows, a coalition of more than 250 tourism-related businesses from five states along the Colorado River, understands that this bumper water year may not bolster the water supply for long, said public affairs representative Molly Mugglestone.

"The bigger take-away is that the Colorado River hasn't reached the Sea of Cortez for about 12 years, so even if we have a lot of snow one year, it's still the overall supply and demand of the Colorado River that's not equal," said Mugglestone. "There is more demand than supply. We're trying to make sure people don't say, 'We've got great runoff this year, no problem.' We're trying to think more long-term in terms of future."

The organization met with Interior Secretary Ken Salazar Tuesday to discuss their stake in the allocation of Colorado River water resources (E&E Daily, July 19).

Andrew Wood of the NOAA Colorado Basin River Forecast Center similarly warned that smart management is necessary to face whatever conditions will affect the crucial river in the future.

"As a result of this year, Lake Powell has reached an equalization level, which means they are able to send water downstream to Lake Mead," said Wood. "But this doesn't restore the lake to levels that were seen before we entered this period of drought. We would definitely need more than a year -- more than even a few years like this."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500

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