Climate change and water overuse have driven the Colorado River to the top of the advocacy group American Rivers’ annual list of endangered rivers.
Decades of drought that some scientists now call permanent aridification have exacerbated chronic overallocation of the waters stored along the river in Lake Powell and Lake Mead. Those reservoirs in turn have shrunken to less than a quarter and a third of their respective capacities, leading federal water managers to call for an emergency cutback in releases to preserve hydropower-generating capacity at Glen Canyon Dam.
“The urgency is extreme,” American Rivers spokesman Sinjin Eberle said, noting that the river serves some 40 million people and production of most of the nation’s winter vegetables. “We have to do something now.”
The group also listed southern Arizona’s San Pedro River among its top 10 because of threats from nearby groundwater pumping.
This spring the U.S. Interior Department has proposed holding back nearly a half-million acre-feet of Colorado River water that under normal operations would flow from Lake Powell through the Grand Canyon to Lake Mead. That would not immediately trigger new shortages among downstream users, but it could in the next few years if runoff from the Rocky Mountains doesn’t improve soon.
This year’s projection is not good. On the heels of two low-flow springs, the Colorado Basin River Forecast Center this month said current snowpack ready to melt suggests just 64% of normal flows will reach Lake Powell this season: 4.1 million acre-feet. An acre-foot — roughly 326,000 gallons — is enough to support a few households in the region, though much of the water is used for agriculture.
“What we’re facing is the permanent warming and drying of the American Southwest,” Colorado State University water and climate scientist Brad Udall said in a statement. His research and outspoken warnings have suggested there’s little time to waste throttling back on water use when rising heat is causing plants and the atmosphere to sponge up springtime runoff before it ever reaches the river.
While water conservation is critical to the region’s future, Udall stresses that controlling climate-changing emissions is too.
“We’re going to need to apply some serious pressure to decision-makers because we are running out of time to solve this problem,” he said.
Low flows threaten river's environment
Interstate negotiators 100 years ago divided the river based on an assumption that it would easily provide more than 15 million acre-feet a year for uses above and below Lake Powell. In this century, though, the river’s flow has averaged closer to 12 million.
The states, tribes and Mexico are now working on new guidelines for sharing shortage, due when the current rules expire in 2026. As the proposal to hold back more water in Lake Powell demonstrates, though, stopgap actions are needed before that.
For its part, Arizona is working with neighbors to pay some users to keep water in Lake Mead over the next few years. These efforts follow a first-ever federal shortage declaration for 2022, which caused Arizona to forego water that otherwise would support Pinal County farms. In response those farmers have planted less and shifted to a declining groundwater supply.
The crisis is harming more than water suppliers’ outlooks. Lower reservoir levels are also limiting options for protecting the river’s own environment, especially in the Grand Canyon.
The prioritization of power generation at Glen Canyon Dam contributed to a decision by the U.S. Bureau of Reclamation not to release water to create an artificial flood to restore beaches and sandbars in Grand Canyon last fall, despite an abundance of rain-driven sand from last year’s monsoon season that had primed the river to deliver the desired results.
And this year, as warm water Lake Powell’s surface drops closer to the hydropower turbine intakes, biologists fear smallmouth bass and other hungry non-native predators in the reservoir are about to slip through and cause havoc in the river below. There, formerly endangered humpback chub were downgraded to “threatened” status last fall, but would face severe losses if bass started eating them.
Scientists briefing an interagency team that works on Glen Canyon Dam’s environmental issues last week said bass seem capable of breeding wherever chubs can, and they lay more eggs. Once they’re in Grand Canyon, they’ll be hard to evict.
“The insidious part of bass is that it only takes a couple,” said Kevin Bestgen, a Colorado State University aquatic ecologist.
Experiments with flushing water from Flaming Gorge Dam, upstream on the Green River, a Colorado River tributary, showed success in dislodging young bass from their protected nests and reducing numbers there, Bestgen told colleagues. A similar effort could make life hard for any bass that get established in Grand Canyon, but would further deplete Lake Powell’s storage.
Migratory birds also require Colorado River water, and reduced supplies will challenge wetland restoration efforts in the delta region around Yuma and in Mexico. Preventing a collapse will require all users and governments in the region to work on keeping more water in the system, National Audubon Society river program director Jennifer Pitt said in a statement.
“Collaboration is the only path to avoid catastrophic water shortages for people and nature,” she said.
Tribes to play a greater management role
The Bureau of Reclamation has pledged to involve regional tribes in its ongoing water management discussion, whereas the tribes in past negotiations have been overlooked. Representatives of the tribes have said dealing with climate change along the river will require working with tribes, a point underscored by the Gila River Indian Community’s key role in providing water for Arizona’s efforts to shore up Lake Mead.
American Rivers provided a video clip of Daryl Vigil, water administrator for the Jicarilla Apache Nation, urging the region to work with tribes.
“Wake up,” Vigil said. “We all know the perilous situation that we’re in right now.”
American Rivers has placed the Colorado or stretches of it atop its list of endangered rivers in past years, sometimes for what it called outdated water management practices and sometimes for threats to Grand Canyon from uranium mining and other development proposals.
Federal infrastructure funding passed by Congress last fall provides billions of dollars that could help with water efficiency throughout the river basin, Eberle said. States are working on conservation plans and on water recycling. The region will need all of it and more, he said.
“We’ve got to amp up the urgency,” he said.
San Pedro River: Water use is drying up stretches of a biodiverse 'ribbon of green'
Most Endangered Rivers
The top 10 “endangered rivers” facing different acute threats this year, according to American Rivers:
1. Colorado River (Western/Southwestern U.S.)
2. Snake River (Idaho, Washington, Oregon)
3. Mobile River (Alabama)
4. Atlantic salmon rivers (Maine)
5. Coosa River (Tennessee, Georgia, Alabama)
6. Mississippi River
7. Lower Kern River (California)
8. San Pedro River (Arizona)
9. Los Angeles River (California)
10. Tar Creek (Oklahoma)
Read the group's reports on each of these rivers at: https://www.americanrivers.org/wp-content/uploads/2022/04/MER2022_Report_Final_04062022.pdf
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This article originally appeared on Arizona Republic: American Rivers urges action on climate-challenged Colorado River