Colorado River forecast: ‘Living beyond our means’
January 17, 2013
GLENWOOD SPRINGS – Planners and engineers in the seven-state Colorado River Basin have spent three years and $4 million to forecast water supply and demand scenarios from now through 2060, and the picture is of a parched future.
“The bottom line is demand is ahead of supply. We are living beyond our means, and the gap is greatest in the Lower Basin,” said David Kanzer, senior water resources engineer for the Colorado River District.
Kanzer presented a summary of the Colorado River Basin Water Supply and Demand Study to the Colorado River District’s 15-member board during the board’s quarterly meeting Tuesday in Glenwood Springs. The 1,500-page study was first released Dec. 12 at a multi-state water users meeting in Las Vegas.
After Kanzer’s presentation, the board convened a closed-door session to discuss the state of Colorado’s negotiation strategy prior to a seven-state meeting next week. Sitting in on the session were Jennifer Gimbel, director of the Colorado Water Conservation Board and the state’s chief water official, and Ted Kowalski, chief of the state water agency’s interstate division.
“We’ll be meeting in Las Vegas next week with the other basin states to figure out what do we do with this study,” Gimbel said.
The basin study was funded by the U.S. Bureau of Reclamation and the seven Colorado River Basin states: the upper basin states of Colorado, Wyoming, Utah and New Mexico, and the lower basin states of Nevada, Arizona and California.
The study is an effort to face up to a future in which millions more people, along with farms and industry, will compete for river flows diminished by the effects of climate change.
“The key assumptions are that demand will go up and supplies will more than likely go down,” Kanzer said. Under the climate change scenario, he said, the forecast is for river flows to fall by 8 to 9 percent.
River flows from 1991 to 2010 past Lee’s Ferry, which is just downstream of Glen Canyon Dam in northern Arizona, averaged 13.7 million acre-feet per year. An acre-foot is 325,851 gallons, or the amount of water covering an acre a foot deep.
Current water use in the basin is 16 million to 17.5 million acre-feet per year, Kanzer said, which includes water from tributaries that drain into the Colorado River below Lee’s Ferry.
The basin study shows that water use has overtopped supply for the past 10 years, and the gap is forecast to continue.
“By 2060, the gap is 3.2 million acre-feet a year, and possibly as much as 8 million acre-feet a year,” Kanzer said.
Lee’s Ferry flows are critical for the upper basin states, as the four states must first send enough water downstream to meet the lower basin’s allocations – 75 million acre-feet in any 10-year period – and can only use water over that amount. So as snowpack and rainfall declines, it will be upper basin users, and western Colorado in particular, that will face limits in water use.
Under some drought scenarios, Kanzer said, “We can run short at Lee’s Ferry as soon as 2020.”
The study evaluates many ways to increase water supply, such as importing water from other basins, cloudseeding, desalinization of seawater, water banking, land use management in watersheds, and changes in reservoir operations. It also looks at options for reducing demand through stepped up urban and agricultural conservation.
“Even with all these scenarios, there will still be times we cannot meet 75 in 10,” Kanzer said, referring to the downstream allocations. “The upper basin shortage risk is real. The Lee’s Ferry deficit is real.”
Moreover, he said, models that assume rising temperatures and changing weather patterns from climate change also forecast the year-to-year variability in streamflow to increase. In other words, there will still be very wet years, such as 2011, and very dry years such as 2002 and 2012, but the very dry years will occur more often in the future.
With the study now published following years of work, water officials are now focused on educating the wider public about the water supply shortfall that Western states will face in the coming decades.
Gimbel said the Colorado Water Conservation Board is planning a “road show” to present study findings in communities around the state, particularly in western Colorado, and on the Front Range, which is heavily dependent on water diversions from Western Slope rivers.
“The first step is education,” Gimbel said. “Then the basin states can make recommendations for short-term and long-term measures.”
To read more about the study, visit the Colorado River District’s website at http://www.crwcd.org.