Water scarcity in Texas reservoirs are not only due to Mexico's lack of deliveries, data shows

SEATTLE - Two water reservoirs in South Texas continue to be at low capacity as drought conditions near the U.S.-Mexico border keep on impacting the region's supply. This has brought pressure on Mexico to make good on commitment to deliver water to the U.S. under a 1944 treaty, although a recent analysis by the International Boundary and Water Commission says that water from U.S. sources has significantly diminished over the years.

Under the treaty, Mexico has an obligation to deliver 1,750,000 acre-feet (AF) of water over a five-year cycle to the U.S. at an average of 350,000 AF annually a five-year cycle. But Mexico is behind on its part of the deal by about 900,000 acre-feet in the current five-year cycle, which ends in October 2025.

Research from the IBWC shows that, even without accounting for water deliveries owed by Mexico, the two international reservoirs that supply water to the Rio Grande were receiving less water than they did decades ago.

Between 2011 and 2020, total U.S. inflow into the Amistad International Reservoir was 33% lower than between 1981 and 1990. an overall decrease of 4.6 million acre feet, according to research from the IBWC.

The Amistad Reservoir, Texas' largest wellspring in terms of acre-feet capacity, is currently sitting at just 19% of capacity while Falcon International Reservoir, which is located about 40 miles southeast of Laredo, is at 12% capacity.

IBWC Commissioner Maria Elena Giner said the decline in water supply highlighted the need for the region to diversify its water supply, as 90% of the region's supply comes from the Rio Grande. "This is something they really need to look at, as far as how they're going to build drought resiliency in the region," Giner said.

Officials in Hidalgo County proposed a regional water supply project in April, dubbed the Delta Water Reclamation Project, that would capture and treat stormwater to be used as drinking water.

After a revision, the project includes plans to build a water plant that would take daily runoff and treat it through reverse osmosis, which consists of pushing water through membranes, large cylinders that filter the water. The process is repeated until the water is pure and meets drinking water standards set by the Texas Commission on Environmental Quality.

Despite the IBWC analysis focusing on how much water was lost from the U.S.'s own tributaries, Giner said getting Mexico to comply with the 1944 treaty was still "front and center" for the agency.

As Mexican officials cited the country's own drought conditions to explain the shortage, Senators Ted Cruz and John Cornyn introduced new legislation that, if approved, would require the U.S. government to impose restrictions on federal aid and prohibit trade and development funds for grantees in Mexico if the country fails to deliver water.

"Mexico has consistently failed to uphold its end of the bargain when it comes to supplying the U.S. with water," Cruz said in a statement. "Mexican officials are now so far in arrears, they will be unable to comply with the treaty and will fall short for the current cycle," Cruz added.