What a Big Water Year Could Mean for the Colorado River and Glen Canyon
by Eric Balken
The 2022/2023 winter is already shaping up to be one for the books. The “atmospheric river” that has pummeled California with rain and snow has also hit the Colorado River Basin, which stands at about 132% of average snowpack as of this writing.
While the deluge of moisture is welcome to the parched west, will it change the outlook and conversation around the Colorado River? The short answer: not likely. There is a lot of winter left and it’s too early to know how big this year’s runoff will really be. A lot depends on spring: how much snowfall we get, but also how warm it will be, and how early it gets warm. This has been the game changer in our modern hydrology.
In recent years, winters with 90% of average snowpack have resulted in runoffs that are 50% of average. This is because our warming climate and aridification are making our runoffs less efficient. We’re seeing warmer springs, earlier snowmelt, warmer summers and falls, and depleted soil moisture that soaks up much of the runoff before it can reach the river. Having a good or even great snowpack doesn’t guarantee a huge runoff, and certainly doesn’t buck long term trends.
We also have to remember where we’re coming from: the combined storage of Powell and Mead is as low as it’s been since Glen Canyon Dam was completed in 1963. The system has been running a 2–3 MAF deficit for more than two decades. Even if we get a tremendous runoff, it will only buy the system another year or so. In a recent interview, climate scientist Brad Udall said, “We would need five or six years at 150% snowpack to refill these reservoirs. And that is extremely unlikely.”
Let’s say we do get a huge runoff. What would that mean for the basin and the side canyons, rivers, and ecosystems emerging in Glen Canyon?
From a policy perspective, it’s likely that Upper Basin states will fight tooth and nail to keep that water in Lake Powell reservoir. But if the runoff is big enough, it could trigger “equalization” where a massive quantity of water is released from Powell to Mead to quickly equalize the two reservoirs. The last time this happened was in 2011, and it was detrimental to the Grand Canyon ecosystem, scouring a large portion of the canyon’s precious sediment away.
In Glen Canyon, the restoring section of Colorado River in Cataract Canyon/Upper Glen Canyon will get a big flush, which could go a long way toward remobilizing sediment that was left behind from the reservoir. In this case, the runoff’s scouring could potentially carve away sediment and bring Cataract and Narrow Canyon one step closer to restoration, while also building large sandy beaches that are critical to rafting recreation and the river’s habitat for flora and fauna.
Of course, if Powell sees a huge influx of water, and it is used to prop up the reservoir, we could see a number of side canyons and emerging ecosystems re-drowned, undoing much of the ecological succession that’s been taking place in recent years. It’s too early to say what kind of elevation change can be expected. Hopefully it wouldn’t drown natural wonders like Gregory Bridge or Cathedral in the Desert, which has seen impressive sediment flushing and new regrowth of maidenhair ferns and hanging gardens.
The big picture is this: while a sizeable runoff will bring much needed relief to the Basin, it won’t be enough to save the system as it stands today. Even if the Basin tackled its water deficit, it would only stabilize the reservoirs, not refill them. We must continue to think about the long term management of the river: where does it make sense to store water in a Colorado River that just doesn’t flow as much as it used to?
If decision makers use surplus years to continue propping up Lake Powell reservoir, how much of its emerging geological wonders, cultural sites, rebounding side canyon ecosystems, and returning mainstem rivers will be lost again? If we can’t even fill half of either reservoir, at what point does it make sense to prioritize Lake Mead first, and let “America’s Lost National Park” continue its unveiling in Glen Canyon?
