In an era when the United States and Mexico aren’t exactly on speaking terms on issues like trade and immigration, there is one issue where both nations are cooperating pretty well: water.

In Santa Fe, N.M., on Wednesday, representatives of the United States, along with the International Boundary and Water Commission, signed their portion of an historic update to a binational treaty with Mexico that could provide some breathing room to Colorado and its portion of the Colorado River. The Mexican government signed its portion of the treaty last week.

Wednesday’s signing of Minute 323 (a minute is an update to an international treaty) brings to a close two years of negotiations over drought on the Colorado and just how that will be handled for the next nine years.

The Colorado starts in Rocky Mountain National Park and its waters are divided, politically, into two regions: the upper Colorado basin states, which includes Colorado, Utah, New Mexico and Wyoming; and the lower Colorado basin states of Nevada, Arizona and California.

As the river moves south, water is diverted into the nation’s two largest reservoirs: Lake Powell, in southern Nevada, and 300 miles to the south, Lake Mead, in Arizona. Hoover Dam, which generates hydroelectric power to the three lower basin states, backs up Lake Mead. Nearly 40 million people in the United States rely on the Colorado, along with up to 5.7 million acres of irrigated agriculture.

In Colorado, the river not only supplies water west of the Continental divide; the river is also one of the primary sources of water for Coloradans east of the divide. As Jim Lochhead, head of Denver Water, recently put it: that glass of water before you gets half of its water from the South Platte River; the other half comes from the Colorado.

Then there’s Mexico. The 1944 treaty between the U.S. and Mexico on the Colorado River guarantees Mexico will receive 1.5 million acre-feet from the Colorado per year. An acre-foot is 326,000 gallons, the amount of water consumed by two families of four annually. But for many years now, the river doesn’t reach it natural destination along  Mexico’s coastline. 

The Colorado has been in drought for the past 16 years in the lower basin and that has affected the ability of the United States to hold up to its end of the bargain on water to Mexico.

While the treaty between the two countries has been in place for more than 70 years, this most recent update attempts to address the environmental problems when there isn’t enough water in the Colorado River delta in Mexico and the critical low water levels that are increasingly seen at Lake Mead and Lake Powell.

Minute 323 is an addendum to the 1944 treaty and updates a previous agreement from 2012 that attempted to address the problems of drought along the lower Colorado basin. This most recent update also has benefits for Colorado, according to James Eklund, who represented the upper basin states in the minute negotiations. Eklund, who once served as Gov. John Hickenlooper’s chief legal counsel and later as the head of the Colorado Water Conservation Board, is now in private practice in Denver.

When water levels drop too much at Lake Mead, which could affect the ability of the Hoover Dam to generate electricity, water is released from Lake Powell to get those levels back up. “Powell is our insurance policy,” Eklund told Colorado Politics after the signing ceremony Wednesday.

Under the revised agreement,

-Mexico will defer delivery of a portion of its Colorado River allotment in case of emergencies, like earthquakes, or based on water conservation efforts in Mexico. The water will be held at Lake Mead. That arrangement boosts Lake Mead levels, which in turn could hold off the need for releases from Lake Powell, the upper basin’s water bank. The agreement said Mexico will gain greater flexibility in how it manages its river allotment.

-Mexico will be provided additional water from the Colorado during “high elevation reservoir conditions” at Lake Mead.

-When Lake Mead levels are low, the update calls for reduced water delivery in order to prevent more severe water reductions. The agreement says this will give certainty to both countries’ operations.

-The United States and Southwestern water providers will invest $31.5 million in water infrastructure and environmental projects in Mexico, in hopes those efforts will generate additional water to be shared by both countries and the environment. This is a second infusion of U.S. funds for the environment and water infrastructure in Mexico.

-Should a “Lower Basin Drought Contingency Plan” be put into place on the U.S. side of the border, Mexico would undertake equivalent water savings, recoverable when reservoir conditions improve.

It’s that last provision that is most critical to Colorado, according to Eklund.

“We in the upper basin have been looking at the situation in the lower basin” for some time, Eklund explained. There is already a drought contingency plan for the upper basin states, but “we have to be very diligent about making sure these drought plans are proceeding at a clip where they’re in place and active before a 2002-type drought hits. If that happens, a water year like that, or two or three years like that, back to back, you’re in bad territory. You have to have tools to deal with that.”

Lochhead told Colorado Politics recently that the update also has major implications for Denver Water. “We stand to lose half our water supply if the obligations are not met,” he said. “We have a direct interest in what happens on the river and how the states and federal government manage that water supply.”

Key to recovery from the 16-year unprecedented drought are programs that will help reduce water use and allow more water to be stored in Powell and Mead. “We can’t do that until Mexico is better integrated into the management of the system,” which the update sets up.

The update calls for Mexico to share water shortages with the lower basin states in the event of an extraordinary drought, which has never been defined. “No one knows what that means and how much Mexico would have to share,” Lochhead said. That’s part of the beauty of the update as well as the 2012 update, both which quantify the amount of water shortage Mexico would take.

With the update in place, lower basin states can start implementing their drought contingency plans, and Lochhead said that could save up to 1 million acre-feet of water in Mead. Upper basin states can start working on “demand reductions” for water that Lochhead said “will keep our bank account in Powell full or at least viable.” Those demand reductions take the form of pilot programs between water providers on the Colorado and farmers. Under this program, farmers are paid not to irrigate on a voluntary and temporary basis. The pilot, Lochhead said, is teaching them about the political and market issues involved in these reductions, which allow the water saved to be moved to Powell.

“If we run into a major problem at Powell,” he said, “we will need to generate about 200,000 acre-feet per year” in savings. It’s doable, but expensive, and has to be managed by all of the states that rely on the Colorado, he said.

Eklund noted that the cooperation between the United States and Mexico on Minute 323 is just one facet of how well the process worked; he also pointed to bipartisan cooperation on the U.S. side of the border among the Democratic and Republican governors of the seven states, nongovernmental organizations and water providers.

U.S. Commissioner Edward Drusina of the International Boundary and Water Commission, which manages the treaty, said Wednesday the agreement “puts us on a path of cooperation rather than conflict as we work with Mexico to address the Colorado River Basin’s many challenges.”