Colorado River U.S. and Mexico agree to share a shrinking Colorado River The two nations are poised to sign an updated water pact to deal with drought.

On a sunny March morning in 2014, dam operators lifted a gate on the Morelos Dam on the Colorado River, at the U.S.-Mexico border. Water gushed toward the river’s dry delta at the Gulf of California. This “pulse flow” coursed downstream for several weeks, nourishing cottonwood and willow saplings and boosting bird and other wildlife populations.

Though most of the water soaked through the parched riverbed to aquifers below, enough remained aboveground to allow the river to meet the gulf for the first time since the late 1990s. That reminded people throughout the basin of the Colorado’s importance — and how humans have altered it. The 2012 international agreement that made the flow possible and addressed other river-management issues expires at the end of 2017. Officials, however, are expected to sign a new pact in the coming weeks. That deal, called “Minute 323,” will extend and expand the previous agreement — and reduce the risk of a catastrophic water shortage that could leave fields and faucets dry.

National Geographic Creative / Alamy Stock Photo

The Colorado River winds 1,450 miles through the U.S. and Mexico. It’s a crucial resource for both countries: Tens of millions of people rely on it for drinking water, and it irrigates millions of acres of farmland. It’s managed according to a complex web of laws, treaties and decisions, including a 1944 treaty specifying how much water the U.S. must send downstream to Mexico each year.

The treaty, which left many details vague or unaddressed, has been updated by hundreds of smaller agreements, called “minutes,” since it was first signed.

For example, though the treaty permits the U.S. to reduce water deliveries to Mexico if there’s an “extraordinary drought,” it does not define that phrase. The 2012 U.S.-Mexico agreement was the first to explicitly state how the two countries should share the bounty of a wet year and the shortages of a dry one. That international accord allows the U.S. to curtail water deliveries to Mexico if the surface of Lake Mead drops below 1,075 feet above sea level, the trigger point at which the Lower Basin states of Arizona, Nevada and California would also begin to face restrictions.

Under the new agreement, Mexico would commit to voluntary reductions in water use beyond those specified in 2012 when Mead drops, according to a summary of Minute 323 several water agencies presented to their boards. But those extra restrictions only go into effect if the U.S. Lower Basin states also agree to similar cutbacks, called the “drought contingency plan.”

That kind of cooperation is critical for the success of basin-wide plans, says Jennifer Pitt, the director of the National Audubon Society’s Colorado River Program and U.S. co-chair of the Minute 323 environmental working group. (High Country News board member Osvel Hinojosa serves as the co-chair from Mexico.) “It only works if they all jump in the pool at the same time.”

The Lower Basin states are still at least a few months away from taking that leap. While water agencies hope to have the drought contingency plan finished by mid-2018, obstacles abound, including conflicts between Arizona water managers and disagreements over the Salton Sea in California, which is fed by Colorado River water. Still, the conditional agreement from Mexico adds an extra incentive for finalizing the Lower Basin plan. After all, “(Mexico) wouldn’t owe any more than they do today if the Lower Basin fails to act,” says Chuck Cullom, the Colorado River programs manager at the Central Arizona Water Conservation District. That would leave the U.S. to face additional water shortages on its own.

Other provisions of the new agreement, which will last for 10 years, tackle lingering logistical issues of international river management. Minute 323 will maintain Mexico’s ability to store water in U.S. reservoirs and address concerns like salinity levels and irregular flow, which can damage infrastructure. The new agreement also stipulates that several U.S. water agencies and the federal government pay Mexico $31.5 million for water conservation projects in exchange for almost 230,000 acre-feet of water. (A typical household uses about half an acre-foot of water per year.) Some of that water will stay in the Colorado system to maintain reservoir levels or help the environment.

Minute 323 will also build upon previous environmental work, including the 2014 pulse flow. The new pact doesn’t explicitly call for another single large release, allowing scientists flexibility in deciding how best to deliver water to restoration sites.

Perhaps the biggest win of the new agreement is that it bolsters transnational cooperation as urgency mounts in the face of climate change. In August, the Bureau of Reclamation announced that there’s “no chance” of water cutbacks in the Colorado River Basin in 2018. Yet the Colorado will continue to shrink in the coming decades. Minute 323 could help the basin meet that challenge.

“It’s one river,” says Tina Shields, a water manager at California’s Imperial Irrigation District. “We don’t want to operate it separately, and we need to have a common understanding.”

Emily Benson is an editorial fellow at High Country News.

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