By Ted Cooke, General Manager, Central Arizona Project (NOTE: The following are remarks made to the Congressional Western Caucus at its March 9 Arizona and Western Policy Roundtable)
I am here to tell a story of seeking balance – balance between using and conserving water.
The Colorado River Basin is divided into an Upper Basin and a Lower Basin. Each Basin has been allocated exactly the same amount of water and there is a U.S. treaty obligation to deliver water to Mexico. There are rules that govern how the Upper Basin is to deliver water to the Lower Basin each year to meet these allocations.
Each basin has a large reservoir – Lake Powell in the Upper Basin and Lake Mead in the Lower Basin. And each reservoir is declining, for different but related reasons.
In the Upper Basin, the Colorado River watershed is in its 19th year of drought, which has reduced the annual runoff into Lake Powell from the historical average. However, since Lake Powell has an obligation to release water to the Lower Basin each year based on the historical allocations, Lake Powell is declining over time.
In the Lower Basin, the allocations to the three Lower Basin States (Arizona, California and Nevada) plus the treaty obligation to Mexico, exceed the normal inflow from Lake Powell. This is because those allocations did not account for losses such as evaporation and seepage. We call this the Structural Deficit. Consequently, Lake Mead also is declining over time.
So, we have drought in the Upper Basin and Structural Deficit in the Lower Basin and two declining reservoirs.
In 2007, all the Basin States and the United States put together guidelines that specified that the two reservoirs were to be operated conjunctively. This means the annual releases from Lake Powell to Lake Mead would reflect the levels of the two lakes relative to each other, thus balancing risk.
Based on the complex rules of these 2007 Guidelines, and because Lake Powell is relatively “more full” than Lake Mead at the present time, the Lower Basin has been enjoying an above-average release from Lake Powell. But this is temporary.
The 2007 Guidelines also define three shortage trigger elevations in Lake Mead. As the lake declines to each of these levels, deliveries to the Lower Basin will be cut back by specified amounts. The lower Lake Mead gets, the higher the cutbacks.
More recently, the Lower Basin States and the U.S. have been working on a Drought Contingency Plan (DCP) that would require additional cutbacks and at higher elevations. This program has not yet been implemented, but we are all working hard to do so, and have actually been achieving “DCP-like” reductions and conserving them in Lake Mead.
The higher releases from Lake Powell, coupled with the carefully managed conservation in the Lower Basin, effectively offset the Structural Deficit and have kept the Lower Basin out of a declared shortage since 2015. Although 2018 is an even poorer runoff year, projections indicate that if a similar level of conservation is employed, the Lower Basin can stay out of shortage for the next two years.
However, this is a temporary “sweet spot.” If poor hydrology continues in the Upper Basin, releases from Lake Powell will be reduced back to “normal” or even lower and shortage will be imminent. The “sweet spot” will be no more.
Once this happens, it does not make sense for the Lower Basin to conserve even more water in an attempt to offset the reductions in Lake Powell releases, because these reductions are two to three times more than the water that the Lower Basin would be cut back under a declared shortage.
Nor does it make sense to attempt to conserve much more water in Lake Mead in advance, since creating relatively higher levels in Lake Mead can precipitate an even earlier reduction in releases from Lake Powell and an even earlier shortage that will wipe out the extra water that might have been conserved.
Furthermore, the opportunity cost of every acre-foot of water that is conserved in the lake is about $60,000, based on the average economic value of use in Arizona.
What a dilemma!
What we need to do, for at least the next two years, is to nurture the “sweet spot” for as long as we can while higher releases are possible by carefully targeting conservation, as has been done for the past four years. And then, instead of leaving every acre-foot we can possibly scrounge up to conserve in Lake Mead, we need to look at how we can use conserved water to mitigate the impacts of shortage and identify the next “sweet spot” where the level of Lake Mead can be stabilized.
DCP will “bend the curve” in Lake Mead and it will eventually stabilize at a lower level than it is right now. We all wish we could keep Lake Mead at its current level indefinitely, but, so long as poor hydrology persists, that is mathematically impossible to do, and DCP, coupled with mitigation, is the plan we have and the plan we must pursue.
Beginning in 2020, the Basin States and U.S. will begin reconsultation on the guidelines and we can then address the solution of longer term issues like the Structural Deficit.
In the meantime, we must find balance – within the rules and programs that we have – between the enormous economic value of water use and the very expensive conservation and mitigation needed to sustain our water supply for the future. We can only do that, as we have in the past, working together constructively and cooperatively.