The 1922 Colorado River Compact received a few revisions last week that negotiators hope will address some of the inefficient uses of the Colorado River, and encourage water districts and developers to make improvements to their systems to make them more efficient, reduce water consumption and to develop alternative plans for drought years when the Colorado River fails to deliver the amount of water allotted as per the 1922 compact. 

The Colorado River Compact of 1922 divides and apportions the use of the water from the Colorado River between Mexico and seven states in the western U.S., which are Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming.

Last week, representatives from the United States and Mexico agreed to renew and expand the conservation agreement that governs how they manage the overused Colorado River, which supplies water to millions of people and to farms in both nations, U.S. water district officials said.

The agreement, to be signed today, calls for the U.S. to invest $31.5 million in conservation improvements in Mexico’s water infrastructure to reduce losses to leaks and other problems, according to officials of U.S. water districts who have seen summaries of the agreement.

The water that the improvements save would be shared by users in both nations and by environmental restoration projects

The deal also calls on Mexico to develop specific plans for reducing consumption if the river runs too low to supply everyone’s needs, said Bill Hasencamp of the Metropolitan Water District of Southern California.

Major river consumers in the U.S. would be required to agree on their own shortage plan before Mexico produces one, he said.

The deal will extend a previous agreement that both countries would share the burden of water supply cutbacks if the river runs low, Hasencamp said.

“It’s good news for both nations, for water users in the U.S. and Mexico,” said Chuck Collum of the Central Arizona Project, another Colorado River user that will help fund the infrastructure improvements in Mexico.

The agreement provides more certainty in how the two countries will deal with the risk of a shortage and recognizes the danger the river faces, he said.

“It’s an acknowledgement that the U.S. and Mexico both share risk due to a hotter and drier future,” Collum said.

The Colorado River is in the midst of a prolonged regional drought. The Colorado River has reached or exceeded its average water level in just three of the last 14 years, and climate scientists expect that trend to continue in future years.

Some climate scientists have said global warming is already reducing the amount of water it carries. A study published in February by researchers from the University of Arizona and Colorado State University said climate change could cut the river’s flow by one-third by the end of the century.

The river begins in the mountains of Colorado and winds 1,400 miles (2,250 kilometers) to Mexico, although heavy use means it usually dries up before it reaches its delta on the Gulf of California where Mexico’s Sonora and Baja California states meet.

Along the way, it supplies water to about 40 million people and 6,300 square miles of farmland in the United States alone. Equivalent figures for Mexico weren’t immediately available.

The deal being signed Wednesday, known as Minute 323, is an amendment to a 1944 U.S.-Mexico treaty that lays out how the two nations share the river. 

The treaty promises Mexico 1.5 million acre-feet of water annually.

The U.S. uses the rest. The average annual flow in the river is about 16.4 million acre-feet, according the U.S. Bureau of Reclamation, which manages the river in the United States.

One acre-foot is enough to supply a typical U.S. family for a year.

The new agreement, which will be in force for nine years, does not include a repeat of the historic 2014 “pulse” that sent about 105,000 acre-feet of water surging into river’s delta in Mexico, the U.S. water officials said.

That was an environmental experiment that brought water and life to the dried-out delta for the first time in years.

But the agreement does include up to 210,000 acre-feet for environmental restoration projects, according to a briefing from Southern California’s Imperial Irrigation District, one of the funders of the Mexican infrastructure projects.

Details of those projects were not immediately available.