Swimmers enjoy the huge spring-fed pool at Balmorhea State Park in West Texas. File photo by Larry Kolvoord/AUSTIN AMERICAN-STATESMAN.

The spring-fed pool at Balmorhea State Park in West Texas closed indefinitely this week due to structural failure.

Crews discovered damage to the concrete apron beneath the diving board, which stabilizes the walls of the pool, during an annual draining and cleaning of the 1.3-acre, V-shaped oasis this week, officials said.

This photo shows damage to the concrete apron near the diving board at Balmorhea Pool. Photo courtesy Texas Parks and Wildlife Department

Officials are evaluating damage and have not set a date for reopening. The closure comes just as temperatures are heating up and the park’s busy season is about to begin. The pool is located about 400 miles west of Austin and is a popular stop for visitors heading to the Big Bend region.

“We are beginning steps to evaluate how much damage is on the pool wall and on the structure. We want to make sure everything is as safe as it can possibly be for everyone, both visitors and the species that call that pool home,” Texas Parks and Wildlife Department spokesperson Stephanie Garcia said.

The site has long attracted people. Native Americans, Spanish explorers and U.S. soldiers watered up at San Solomon Springs, which pumps out about 15.5 million gallons of water a day, long before the Civilian Conservation Corps turned the desert wetland into a pool in the 1930s. Private concessionaires operated the park until the 1960s, when the Texas Parks and Wildlife Department took it over.

Balmorhea State Park in west Texas on a hot July day. Jay Godwin/American-Statesman

Today visitors flock from around the state to dip a toe or two into the enormous pool, 25 feet deep in places, with a natural bottom. Swimming there feels like gliding through a giant aquarium populated by fish of all sizes. It holds 3.5 million gallons of water, and water temperatures hover between 72 and 76 degrees year-round.

More than 153,000 people visited the park between Sept. 1, 2016 and Sept. 1, 2017. On hot summer weekends, the park fills to capacity by noon and cars are turned away.

The pool has environmental significance, too. It’s home to two small, endangered desert fish – the Pecos gambusia and the Comanche Springs pupfish.

Habitats have been created outside of the pool for the protection of the fish and other invertebrates, and officials say they are working to protect the species during the closure.

RELATED: Take a dip in a desert oasis at Balmorhea Pool

The 45-acre desert park’s day use and picnic area will remain open while the pool is closed.

The park’s retro, adobe-style 18-unit motor court closed early this year for renovations and should reopen in 2019.

“Balmorhea State Park is a treasured oasis in west Texas that has provided unique recreational opportunities for generations of Texans,” Brent Leisure, director of Texas State Parks, said in a press release. “Our staff is working diligently to address the situation and make the pool is safe for the visitors and the aquatic life in habitats associated with the San Solomon Springs.”

For more information about the park, call (432) 375-2370.