Mitchell Lake in San Antonio drawing birds, human attention

By SCOTT HUDDLESTON, San Antonio Express-News

SAN ANTONIO — Mitchell Lake served for decades as a big, stinky holding pond for San Antonio's sewage, but now it is considered a hidden gem on the South Side as a refuge for hundreds of bird species.

The San Antonio Express-News reports owls, roadrunners, sandpipers, herons, hawks, pelicans and even whooping cranes, an endangered species, live at the 1,200-acre natural area or have been spotted there as they migrate.

Soon, the area will be the site of a yearlong pilot program to find out whether restoration of wetlands at the lake could improve its water quality.

One key concern is the algae at the bottom of the 600-acre shallow lake. The algae increases nitrogen and diminishes dissolved oxygen that is critical to fish and other wildlife during heavy rains. The water flows south into the Medina and San Antonio rivers.

The algae built up over time. The city acquired the lake in 1901 and began pumping sewage into it through an open ditch. That continued after a wastewater plant was built in the 1930s. The Legislature ordered a cleanup of the lake in 1973. Dikes and basins were built, and sewage discharges were discontinued in 1987.

The lake, now part of the San Antonio Water System, is still regulated as a federally and state-permitted wastewater treatment plant, SAWS President and CEO Robert Puente said. The state considers it a violation, because of the elevated nitrogen levels, when water spills over a dam on the south end of the lake.

SAWS considered several possible solutions to the water quality problem, including raising the dam, building a wastewater treatment plant at the lake or dredging it.

Because of the lake's conversion in recent decades into a haven for waterfowl and "a jewel of San Antonio," SAWS opted to seek a natural solution, Puente said.

Under the pilot program, set to begin early next year, 1.8 acres at the southwest corner of the lake will be replanted with cattails and other aquatic plants. Those could help reduce the algae and nitrogen, as directed by the federal Environmental Protection Agency.

"It could turn out that it doesn't work. We think that it should," said Sam Mills, special projects director at SAWS.

The U.S. Army Corps of Engineers allocated $1.5 million for the test project. If it proves successful, SAWS plans to modify the dam to manually control spillway flows. That would allow water to continually feed up to 120 acres of potential wetlands south of the dam, typically at depths of 6 inches to 2 feet, providing cleaner water as it moves downstream.

Nearly 350 bird species have been documented at the lake, which dates to at least 1764, when a Spanish map indicated a body of water at the site.

The nonprofit Mitchell Lake Audubon Center, part of the National Audubon Society, operates the natural area under a contract with SAWS and offers tours and classes.

Over time, hiking trails, bridges, a visitors center and restrooms have been added.

U.S. Reps. Will Hurd, R-San Antonio, and Henry Cuellar, D-Laredo, helped secure the money. Cuellar said the lake, which is open to the public, typically from 7 a.m. to 2 p.m. Tuesday through Sunday, has about 10,000 visitors and more than 100 bird-watching tours annually.

"This will have a lasting impact on this area," Cuellar said at a ceremony last week.

Hurd said anyone who visits Mitchell Lake can become a birder.

"You can come to the South Side of San Antonio to see hundreds of pelicans in the middle of the year. That's crazy to me," he said.

Puente, referencing $13 million included in a 2017 bond issue for a land bridge at Hardberger Park on the North Side, said he hopes a future bond issue, possibly in 2022, will include money for Mitchell Lake.

The money could "continue what we're trying to do to make this a true destination place for the entire world," complementing the four Spanish colonial missions and other places of interest on the South Side.

"I'm saying right now, we need to do that," Puente added.

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