River draining uncovers plenty of junk — and invasive species
Biennial cleaning includes adding native plants and removing apple snails
At the corner of Alamo and Commerce streets, a dumpster is packed with folding chairs, fiesta beads, a stroller, Christmas lights, a baby doll and a toy gorilla. All are covered in dried mud and silt, and all were removed from the San Antonio River downtown this week.
The San Antonio Public Works Department on Monday began draining parts of the river that flow through downtown for cleaning and maintenance, digging deep to find trash that has accumulated below the surface since the last time the river was drained two years ago. The project — which spans the downtown river loop, the extension and a segment of the main channel — will continue until this weekend, when public works will refill the river.
While the water is low, the city will check the floodgates, inspect sensors and gauges that monitor water levels, and make repairs. At the same time, the San Antonio River Authority will remove non-native invasive species, plant native aquatic plants and temporarily move native species until the project is completed.
“The River Walk area is world famous, and we feel a great responsibility to keep it beautiful and attractive to residents, as well as tourists,” said Nefi Garza, assistant director of Public Works. “One of the best ways to do this is to periodically drain the river.”
The biennial river draining is normally done during winter so that it doesn’t disrupt more active tourist periods and to avoid the stench that would accompany warmer temperatures.
Chris Vaughn, a senior aquatic biologist at SARA, said that every two years is a good frequency for biological river maintenance. The SARA team on Monday walked through the drained areas from Pearl to Lexington Avenue, looking for invasive species. Before that, SARA had moved native fish — such as large
mouth bass, western mosquitofish and red shiners — to undrained parts of the river for the week.
This year, the team has found about 500 non-native apple snails, which they removed from the river and donated to Southwestern University. It is also looking for non-native fish, such as blue tilapia, sailfin catfish and common aquarium fish, such as suckermouth catfish.
Zebra mussels, which are among SARA’S largest invasive concerns, are not a problem yet, but the team is monitoring closely for them.
“It’s all about control,” Vaughn said. “We can’t really eradicate a non-invasive species like this. I mean, there’s so many pockets of mud and things like that that the apple snails burrow down into this time of year, but we do try our best to keep the numbers down.”
An urban river system, such as the San Antonio River, is at a disadvantage due to reduced water quality and a greater propensity to accumulate trash, which can harm native species, Vaughn said. Meanwhile, many non-native species can survive in polluted water.
Between river maintenance, the city and SARA encourage residents to keep trash out of the river. Dumping the contents of household aquariums into any Texas body of water can spread invasive species and harm the ecosystem.
“Mistakes happen, and chairs fall in there. That’s
part of the maintenance that we do,” Garza said. “But the other thing is we really want to encourage visitors and residents to understand the
natural value of the river.”