McALLEN, Texas (Border Report) — The United States and Mexico have agreed to share costs to repair dozens of sinkholes and leaks in Amistad International Dam, which straddles the U.S.-Mexico border in South Texas.

Under a change to the 1944 international water treaty, the United States has pledged to pay 56.2% of the costs and Mexico will pay 43.8% of the costs associated with the repairs, the International Boundary and Water Commission announced Monday.

The agreement was signed on Dec. 10 in El Paso and has been approved by both governments. It will allow “structural safety measures that must be implemented to reduce the risk of failure at Amistad International Dam due to the presence of sinkholes and seepage,” according to the 37-page agreement obtained by Border Report.

Repairs will include fixing 55 sinkholes on Mexico’s portion of the dam’s earthen embankment, the IBWC says.

Engineers from the United States and Mexico study sinkholes in Amistad International Dam. (IBWC Courtesy Photos)

“We are collaborating with Mexico on the technical expertise and cost involved in rehabilitating Amistad Dam,” U.S. IBWC Commissioner Maria-Elena Giner said in a statement. “Experts from both countries determined the recent discovery of additional sinkholes was a cause for concern, but not alarm. We are continually monitoring the safety of this dam and will keep the surrounding area informed of the progress of this project.”

Last January, the Amistad Dam Port of Entry, which connects to the Mexican state of Coahuila, was temporarily closed for maintenance relating to the sinkholes. That was shortly after the U.S. Army Corps of Engineers declared the dam “potentially unsafe,” Giner said.

In the agreement signed earlier this month, both countries stated: “Works for the construction of the Composite Cutoff Wall on the Mexican side of Amistad Dam’s earthen embankment are declared to be of an extraordinary or emergency nature.”

Mexico has pledged $20 million for Phase I of the reconstruction costs.

Repairs will be carried out in two phases: contracting for project design and contracting for construction.

The design of the project began on Sept. 17 and is expected to be finished in March. Once construction begins, it is expected to take 30 months.

“For the United States and Mexico and for IBWC, it is fundamental to ensure the safety of Amistad Dam,” Mexican IBWC Commissioner Adriana Reséndez said. “The design and construction of this important project is being done in a joint and coordinated manner between the two countries in order to ensure all the technical aspects inherent to it.”

The dam has been losing water for years. “Most of this seepage is traveling through the foundation of karstic limestone,” according to an Oct. 8 joint report by principal engineers from both countries who have been studying this issue.

The recent water loss comes at a critical time for the South Texas border region, which has been reeling from months of dry weather, drought and overpopulation.

Under the 1944 treaty, Mexico must pay the United States 1.75 million acre-feet of water every five years to the Rio Grande. The current cycle ends in October and Mexico has only paid 432,048 acre-feet, according to the IBWC.

Water levels at Amistad were at 21% on Tuesday and at 13% at Falcon Dam in Starr County, the IBWC reports.

At the start of 2024, the state’s only sugar mill in Hidalgo County closed due to a lack of water. Citrus and other crops in the Rio Grande Valley are threatened by a lack of water, as are municipalities and farmers.

Amistad Dam is 12 miles north of the border cities of Del Rio, Texas, and Ciudad Acuña, Mexico. Construction on the 6-mile-long dam began in 1963 and was completed in 1969 as the second international storage dam built jointly by both countries under the 1944 Water Treaty.

A 2020 U.S. Army Corps of Engineers report found the dam and lake provide over $76 million in annual public benefits to the United States, including $8 million for flood risk management; $9 million for hydropower; $7 million for water supply — both industrial and municipal; $8 million for irrigation; and $44 million for recreation, fish and wildlife.

South Texas lawmakers are praising the agreement.

“From providing irrigation water storage to generating electricity, the Amistad Dam is a critical resource to South Texas,” U.S. Sen. John Cornyn said. “Every drop of water saved is vital to communities in the Rio Grande Valley, and I appreciate the IBWC for working to ensure areas of the dam impacted by sinkholes and seepage are restored.”

U.S. Rep. Henry Cuellar, D-Texas, said he was pleased that Mexico and the United States have agreed to rehabilitate the dam.

“This critical project will ensure that water is stored securely as well as bolster an integral energy source in South Texas,” Cuellar said. “Furthermore, the Amistad Dam is important for other activities including recreational and fishing opportunities.”

U.S. Rep. Vicente Gonzalez, D-Texas, said Amistad Dam is crucial to the Rio Grande’s water conservation infrastructure.

“It protects South Texas from the devastating impacts of flooding while also providing a supply of water for our municipalities, agriculture producers, and irrigation districts,” he said. “I am pleased that this agreement was signed and that IBWC has begun the rehabilitation of Amistad Dam to ensure it can continue to operate and serve the Rio Grande Valley.”

Sandra Sanchez can be reached at SSanchez@BorderReport.com.