Water-supply cuts would hit Ariz. first

Drought in the Colorado River basin could soon force a cut in water deliveries, but Southern California is unlikely to be affected, according to a federal report released Wednesday.

The U.S. Bureau of Reclamation document examines the effects of four proposals for handling shortages on the river, which is suffering from the worst drought in a century and one of the most severe in 500 years. “There is a chance in three years we would have a shortage. It’s not a certainty,” said Terry Fulp, a manager in the reclamation bureau’s lower Colorado region.

Under the complex set of laws and water rights that govern the Colorado River, Arizona agriculture would be the first to face a cut in deliveries to the lower basin. Cities in that state would be less affected, although the river communities of Lake Havasu City and Bullhead City could lose roughly a quarter of their supplies.

If the drought deepened, other cities would also be affected, said Thomas Carr, assistant director of the Arizona Department of Water Resources.

Las Vegas, too, could lose some of its allocation, but the reclamation report concludes that overall, municipalities will be able to cope with the cutbacks with little impact on their economies by implementing their own drought plans. Carr said Arizona would provide the river towns with other supplies to counter their Colorado losses, although they would eventually have to repay the state water bank.

In California, most of the state’s large river share is used by Imperial Valley agriculture, whose senior rights largely insulate it from cutbacks. The state’s junior user is the Metropolitan Water District of Southern California, the region’s major urban supplier, but it would require a large shortage to trigger cuts to the agency. “We have a good position in the river,” said Metropolitan assistant general manager Roger Patterson.

The Department of the Interior, which oversees the Colorado’s management, is expected to adopt a drought-management plan by the end of the year. Of the four proposals evaluated in the reclamation report, the one made by the seven basin states is considered to have the best chance of approval.

It is designed to avoid a legal brawl among the states by allowing changes in management of the system’s two main reservoirs, Lake Mead and Lake Powell, without altering river law.

“This is a combination of things that seemed to make a lot of sense,” Patterson said. “Nobody wants to give up legal arguments that we may need to make down the road. Yet, we’ve got pressing needs, so the parties have to try to make things work.”

The states’ plan would, for instance, allow Metropolitan and other water agencies to store water they had saved in Lake Mead -- maintaining the reservoir above levels that would trigger delivery cuts. That has not been permitted under river law, which requires states to take their allocations from the Colorado every year or lose them.

The Southern Nevada Water Authority would also pay for construction of a small reservoir off the river, next to the All-American Canal just north of the Mexican border. The reservoir would hold water that would otherwise be lost to Mexico when farmers order deliveries but then don’t need them because of rain.

Environmentalists proposed another plan under which the federal government would maintain lower basin deliveries by buying supplies from willing sellers in agriculture.

Jennifer Pitt, senior resources analyst for the group Environmental Defense, said that while the state plan injects needed flexibility into river management, it could also harm the environment. The flows that would be caught by the new reservoir, for instance, now give a much-needed shot of water to the Colorado’s degraded Mexican delta.

“If we push efficiency to the limit not only in the U.S. but in Mexico, we guarantee the demise of the delta environment,” Pitt warned.

bettina.boxall@latimes.com