The deal transfers Mexico's share of water held in the Amistad and Falcon dams to U.S. ownership. The amount of water transferred is enormous: 170 million cubic yards (130 million cubic meters), or enough water to flood 105,000 acres with a foot of water.
Mexico said it still had enough water in other dams near the border to satisfy drinking water requirements for 13 border cities including Nuevo Laredo, Reynosa and Matamoros. The United States also agreed to help Mexico if it faces a municipal water shortage.
Mexico says the agreement will leave it with some water in the border dams it can draw on — about a three-month supply — and more water in near-border dams to supply cities and towns, mainly in the state of Tamaulipas.
Under the 1944 treaty, the quantity of water Mexico ships north from the central section of the border is only a fourth of what it receives from the U.S. along the Colorado River to the west, and it has been worried about the possibility of losing that.
Mexico was embarrassed when, over the summer, angry farmers in the border state of Chihuahua has seized a key dam there and refused to allow any more water transfers to the United States, claiming they needed the water for their own crops.
But in the end, the surprising friendly relationship that leftist President Andrés Manuel López Obrador has maintained with U.S. President Donald Trump allowed Mexico to gain a face-saving last-minute deal, and Mexican officials appeared grateful for that.
“We want to thank (U.S.) Secretary of State Mike Pompeo and all his team for their support in reaching this agreement,” said Foreign Relations Secretary Marcel Ebrard.
López Obrador noted recently that unlike 2016, candidates in the November presidential race have been “respectful” of Mexico and he wants to keep it that way.
As a candidate in 2016, Donald Trump accused Mexico of sending rapists across the border. But the rhetoric this year has been softer.
The agreement “also establishes work groups to analyze and develop water management tools to provide for increased reliability and predictability in Rio Grande water deliveries to users in the United States and Mexico," according to the International Boundary and Water Commission, which oversees the implementation of the treaty.
The problem arose in part because of a lack of rainfall, but also because Mexico has long pursued a strategy of falling behind in water payments, hoping for a last-minute storm or hurricane that would fill border dams and streams and allow it to recoup shortfalls.