Powell: A lake in need of a break
Reservoir unlikely to meet its water-release obligations next year
When states in the lower Colorado River Basin agreed to 2007 criteria under which Lake Powell could potentially provide them less than the normally required amount of water, they “probably never thought it would happen,” says Eric Kuhn, general manager of the Colorado River District.
Now the unthinkable is appearing likely. Under current hydrological projections, it’s expected that the 2007 provision will kick in, providing for Powell to pass on 7.48 million acre-feet in the 2014 water year, which starts Oct. 1.
It normally is obligated to release at least 8.23 million acre-feet per year. While it has come up a bit short some years due to measurement errors, it probably has never released fewer than about 8 million acre-feet annually since Powell first filled after completion of Glen Canyon Dam, said hydraulic engineer Katrina Grantz of the U.S. Bureau of Reclamation’s Upper Colorado Region.
This is what happens when the region experiences the driest 14 years on record, with just three years of above-average precipitation, and drought conditions the last two winters. Kuhn said this year “is shaping up to be one of the four or five driest years for inflow into Lake Powell.”
A total of just 4.43 million acre-feet of water, or 41 percent of average, is expected to flow into Lake Powell this water year—not quite half of what will have flowed out. It’s expected to be holding just 10.5 million acre-feet by Sept. 30, just a few million acre-feet more than it releases each year, and 43 percent of capacity. An acre-foot is about 326,000 gallons.
“I don’t know that I would use the word ‘problem’ exactly but it’s dry. We’re very lucky we have the storage we have to carry us through these dry periods,” Grantz said.
Gary Wockner, campaign coordinator for the group Save the Colorado, considers the situation more dire.
“The bottom line is that more water is being taken out from the system than is flowing into the system and it absolutely is unsustainable,” he said.
Indeed, Bureau of Reclamation data indicates that its total reservoir storage in the Colorado River Basin by Sept. 30 is projected to be at 49 percent of capacity, at about 28.9 million acre-feet, Grantz said. The previous low since Powell was first filled was 50 percent, in 2004.
Combined, Powell and Lake Mead are projected this fall to reach their lowest percentage of capacity since Powell’s filling, at 45 percent, or 22.6 million acre-feet, compared to a previous low of 46 percent in 2004.
Powell’s current predicament comes as the Bureau of Reclamation also is considering ways of trying to head-off what it has projected could be an annual shortfall of 3.2 million acre-feet by 2060 in the Colorado River Basin.
Wockner notes that more projects are planned to use diverted Colorado River water along the Front Range.
“You can’t take any more water out of the system without it impacting someone else’s water supply,” he said.
Potentially historic lows
Current projections have Powell dropping by the end of 2014 to an elevation within about 10 feet of its low point in 2004, Grantz said. By early 2005, Powell reached its lowest level since it first filled.
History suggests it’s a time for concern, but not panic. In 2010 water-watchers were worried about low water levels in Lake Mead, but then came epic winter snows.
“That bought three years of relief, probably,” Kuhn said.
Said Grantz, “One big (water) year can really help us out a lot.”
Indeed, part of the reason Powell will be able to release less water is because Mead will be high enough under the 2007 criteria to make do with less. Those same criteria allow for increased releases from Powell under certain circumstances to help Mead.
For Kuhn, “The real concern is, what happens if next year’s dry?”
Grantz said the Bureau of Reclamation is expecting a below-average runoff year next year, partly because soil is so parched that precipitation is more likely to be absorbed by it rather than reaching streams.
Kuhn fears that could lead to low enough water by 2015 that it could start to affect hydroelectric production at Glen Canyon Dam. He said water less than 25 or 30 feet above the power plant intakes could be low enough for a vortex to form, damaging turbine blades.
Revenue from that plant helps pay for river hydroelectric projects and operation and maintenance of electric lines, as well as programs such as endangered fish recovery.
Grantz said the Bureau of Reclamation believes it would take three or more years of continuing dry conditions before power-generation problems could arise.
Kuhn also believes the reduced release of water from Powell next year would likely result in the declaration of a first-ever water shortage for Nevada, Arizona and Mexico by 2015 or 2016. While the reductions they would experience wouldn’t necessarily cause great hardship at first, that would change if the shortage declaration went into a second year, he predicts.
Kuhn said some of his concerns remain hypothetical ones until it’s known what this winter brings. But at the same time, he said planning ahead for possible continued drought provides more flexibility than waiting until next April to act.
One thing that strikes him is that even while the river is currently challenged at a systemwide level, that isn’t necessarily reflected in local-level decisionmaking. For example, Denver Water recently eased its watering restrictions after late-season snow resulted in its reservoirs filling.
How much water is in Lake Powell may not greatly concern a lot of upstream municipalities and other water users, but Kuhn believes it should, given the need to meet downstream obligations.
“I think in future drought years we’re going to have to have a system in place so as Powell approaches these lower levels we start to cut back” consumption, he said.
When Denver eased its restrictions, it asked residents to continue using less, citing the need for everyone to do their part to protect against the possibility of another dry winter.