Opinion: The chances are increasing for lakes Mead and Powell to reach dangerously low levels. There are basically two solutions, and neither will be easy.
Lake Mead and Lake Powell are in trouble.
It’s hard to view the latest five-year projections released from the federal Bureau of Reclamation any other way.
Projection of Lake Mead end-of-December reservoir elevations. The colored region, or cloud, for the hydrology scenario represents the minimum, 10th percentile, 90th percentile, and maximum of the projected reservoir elevations. Solid lines represent historical elevations (black), and median projected elevations for the scenario (yellow). Dashed gray lines represent important elevations for operations, and the vertical line marks the adoption of the 2019 Drought Contingency Plans. Graphic credit: Bureau of Reclamation
At Lake Mead – the reservoir Arizona depends on for about 40% of its water supply – there is now a 66% chance of falling below 1,025 feet of elevation in 2025. And a 41% chance of enacting a Tier 3 shortage that year, the worst for which we have planned and one that would begin cutting into the supplies that feed metro Phoenix’s major cities.
That’s up from a 25% chance in April.
There also is a 1 in 5 chance of dipping below 1,000 feet of elevation in 2025, a dangerously low level that would likely force Hoover Dam, which supplies hydropower to 1.3 million people, to cease production.
Projection of Lake Powell end-of-December reservoir elevations. The colored region, or cloud, for the hydrology scenario represents the minimum, 10th percentile, 90th percentile, and maximum of the projected reservoir elevations. Solid lines represent historical elevations (black), and median projected elevations for the scenario (yellow). Dashed gray lines represent important elevations for operations, and the vertical line marks the adoption of the 2019 Drought Contingency Plans. Graphic credit: Bureau of Reclamation
The scenarios are just as bad on Lake Powell – or maybe worse, considering it is facing the possibility of turning off its generators much sooner. There is an 88% chance of dipping below 3,525 feet of elevation next year (a buffer meant to help protect power production) and a 1 in 3 chance of falling below 3,490 feet in 2023 – the point at which power can no longer be generated.
That would cause immediate problems for the 5 million people that rely on this power, not to mention nix revenues from generation that are used to fund a slew of programs along the Colorado River.
This forecast is our ‘new normal’
It’s important to understand how Reclamation arrived at these projections. The agency has in recent years begun using what’s called the “stress test hydrology” in its modeling, which is based on runoff for the last three decades or so.
But until this forecast, that hydrology was used as a supplement. The model also included projections based on the “full hydrology,” which also includes decades of unusually wet years.
The September update includes only the stress test – which as water blogger John Fleck noted, makes it the “new normal.”
The stress test is hardly the worst-case scenario for the Colorado River. Some consider it more of the middle-of-the-road view – not the hotter, drier future we are expected to experience (and may already now be experiencing), thanks to climate change.
Still, it’s a more realistic forecast that should help us get a better handle on how extensive the problem is and what we must do to fix it.
Mead is tanking because Powell is tanking
Mead is in trouble because Powell is in trouble.
Low inflows plus steady demand for the water have drained Powell far quicker than most folks imagined. Mead relies on annual releases from this upstream reservoir to stay somewhat stable, and because Powell is so low, the most likely scenario for the next few years involves a much smaller release (7.48 million acre-feet, as compared to the 8.23 million acre-feet we typically receive).
Those forecast lower releases have already triggered a provision requiring the lower basin states of Arizona, California and Nevada to decide what additional steps they’ll take to prop up lake levels.
Tom Buschatzke, Arizona’s water department director, has said there are basically two options, given the urgency: Either we agree to deeper, more painful cuts, or we find others willing to voluntarily store more water in the lake to cushion the blow.
Neither is a long-term solution, but that’s not the goal. It’s simply to buy time while we figure out how to sustain ourselves given this new, drier reality.
We need more than a Band-Aid to stabilize the lakes
If this sounds familiar, it’s because it is.
Mead was facing roughly a 1 in 5 chance of dipping below 1,000 feet before we passed the Drought Contingency Plan in 2019. And make no mistake: Were it not for that plan, we would be in much worse shape today.
But its million acre-feet in cuts has always been a Band-Aid – one that, unfortunately, has not protected the wound long enough to even begin to heal.
If anything, Reclamation’s latest forecast is proof that we must do more to ensure that what we consume from the Colorado River better matches what the river can realistically produce now.
Other modeling has suggested that we could find that equilibrium if the upper basin states agree not to grow their water usage, as they have long planned, and the lower basin remains in roughly a Tier 3 shortage from here on out.
