#ColoradoRiver study means it’s time to cut #water use now, outside experts say — #Tucson.com #COriver #Aridification

From The Associated Press (John Locher) via Tucson.com:

Less water for the Central Arizona Project — but not zero water.

Even more competition between farms and cities for dwindling Colorado River supplies than there is now.

More urgency to cut water use rather than wait for seven river basin states to approve new guidelines in 2025 for operating the river’s reservoirs.

That’s where Arizona and the Southwest are heading with water, say experts and environmental advocates following publication of a dire new academic study on the Colorado River’s future.

The study warned that the river’s Upper and Lower basin states must sustain severe cuts in river water use to keep its reservoir system from collapsing due to lack of water.

That’s due to continued warming weather and other symptoms of human-caused climate change, the study said.

The study from Utah State University said Arizona and the other two Lower River Basin states may have to slash their take from the river up to 40% by 2050 to keep reservoirs from falling too low. The other Lower Basin states are California and Nevada.

The study also says the four Upper Basin states must dramatically scale back or kill plans to divert more water from an already depleted river. Those states are Colorado, New Mexico, Utah and Wyoming.

The study appeared as the seven states are preparing to renegotiate the operating guidelines that expire at the end of 2025.

More immediately, the first cutbacks in Central Arizona Project deliveries from the river — primarily to Central Arizona farmers — appear likely for next year…

Eric Kuhn, one of the new study’s co-authors, speculated that over time, the Central Arizona Project will make a bunch of deals with irrigators along the river to buy water rights, following the footsteps of Colorado and Southern California water transfers.

“CAP water flows uphill to the money. Municipalities in Central Arizona have political power and money. How many votes are there along the river vs. how many votes there are in Maricopa County?” said Kuhn, retired director of the Colorado River Water District in Glenwood Springs.

It’s pretty clear the Imperial Irrigation District, the river basin’s largest water user by far, will also be a target for future water transactions to help cities, [Mark] Udall said. Imperial takes more than one-third of the Lower Basin’s 7.5 million acre-feet annual supply from the river…

Upcoming negotiations: Arizona’s top water officials and some outside water experts and activists are taking different stances toward the impending seven-state river negotiations.

Those talks should start sometime this year, although the Bureau of Reclamation, which runs the reservoirs, isn’t being specific on when.

It’s working on developing a plan “that ensures that all of our partners on the river are able to participate and contribute in a collaborative and meaningful way,” bureau spokeswoman Patricia Aaron said…

Reacting to the negotiations and the new study, a CAP official said that agency has long understood risks to the Colorado River system associated with a hotter, drier future, and realizes that more work is needed to address them for the longer term…

The state has a good start in preparing for the seven-state talks, thanks to the structure of water interest groups the state assembled to put together the 2019 drought plan, said ADWR Director Tom Buschatzke.

“We anticipate looking at a variety of hydrologic futures, how they might impact lake levels, how we might protect those lake levels under those hydrologic scenarios, as well as how our efforts might equate to the frequency or magnitude of reductions,” Buschatzke said…

Retiring coal-fired power plants faster than now planned can save water because they use a lot, Bahr said.

Having water priced more “appropriately” — charging more for water use beyond what homeowners need for drinking, cooking and bathing, is also advisable, she said — something Tucson already does in its water rate structure.