The health of our waters is the principal measure of how we live on the land — Luna Leopold
First-ever #ColoradoRiver water shortage is now almost certain, new projections show — CNN #COriver #aridification
At full pool, Lake Mead is the largest reservoir in the United States by volume, but two decades of drought have dramatically dropped the water level behind Hoover Dam as can be seen in this photo. (Source: U.S. Bureau of Reclamation)
On Tuesday, the water level in Lake Mead — the largest US reservoir, and fed by the Colorado River — fell below the elevation of 1,075 feet. It has hit that mark only a handful of times since the Hoover Dam was finished in the 1930s, but it always recovered shortly after. It may not this time, at least not any time soon.
The US Bureau of Reclamation (USBR) forecasts the lake’s levels to continue to decline, without any sign of recovery through at least the end of 2022. If the next major study in August from the USBR projects water levels in the lake will be below 1,075 feet on January 1, it would trigger the first-ever shortage declaration on the Colorado River, meaning some communities would begin to see their water deliveries cut significantly next year.
Lake Mead and nearby Lake Powell — the two largest reservoirs on the Colorado River — have drained at an alarming rate. Lake Mead has fallen more than 139 feet since January of 2000.
Lake Mead is currently 16 feet below where it was this time last year and the reservoir is only 37% full, while Lake Powell is down 35 feet from last year and sits at just 34% of the lake’s total capacity.
Glen Canyon Dam on the Colorado River in April 2017. The dam is 15 miles upstream from Lees Ferry, Arizona. The Colorado River, which supplies water to more than 40 million people and irrigates millions of acres of farmland, has seen its supply sapped by drought and climate change. Photo by Alexander Stephens/courtesy Bureau of Reclamation.
In addition to dwindling snowpack, which provides most of the river’s water supply, experts say dry, thirsty soils across the basin are soaking up meltwater, meaning that less makes it into the river system…
Climate change is also taking a toll on the river’s water supply. A study by US Geological Survey scientists published in 2020 found that the Colorado River’s flow has declined by about 20% over the last century, and over half of that decline can be attributed to warming temperatures across the basin.
Who would the shortage affect?
With the level of Lake Mead dipping below 1,075 feet on Tuesday and forecast to drop further, it is nearly certain that the Bureau of Reclamation will declare a Tier 1 shortage later this summer.
If a Tier 1 shortage is declared, Colorado River water deliveries would be reduced for Arizona and Nevada as soon as next year, based on the terms of the 2019 drought contingency plan signed by the lower Colorado River basin states.
The looming water cuts will have the greatest impact in Arizona.
As part of the lower basin’s drought contingency plan, the Central Arizona Project would see its water supply slashed by about one third in 2022 due to its junior rights to the river’s water.
While Arizona’s main population centers will be spared, the effects of those water cuts will be felt most acutely on farms in central Arizona, due to their lower priority status in a complex tier system used to determine who loses water first in the event of a shortage.
California’s water deliveries would not be impacted in a Tier 1 shortage, according to the drought contingency plan.
What happens if Lake Mead sinks further?
In the event of a Tier 2 shortage — which the USBR projects could happen as soon as late 2022 — the cuts would impact some cities and tribes in Arizona that receive water from the Central Arizona Project canal.
“I’m definitely concerned that the raw projections continue to go downward and that we are heading towards potentially a Tier 2 [shortage] in 2023,” said Tom Buschatzke, director of the Arizona Department of Water Resources.
