Invasive South American snails and electric scooters are among the things crews are pulling from the dried-out bed of the San Antonio River this week after workers drained the downtown channel for the first time in four years.
As of Monday afternoon, the City’s Transportation and Capital Improvements (TCI) department, working with the San Antonio River Authority, had drained the river’s main channel from East Josephine Street to South Alamo Street. The channel will remain drained until the end of the week.
Though the river’s main channel is dry, the tourist-heavy horseshoe-shaped bend lined with shops and restaurants remains full of water, cut off by flood gates. The City drains that section less frequently because of its sensitive retaining walls, according to TCI officials. The last time was around six years ago.
While cleaning is the main focus, the draining offers biologists a chance to remove invasive fish and other species that throw the river’s ecosystem off-balance. The apple snail, a popular home aquarium species first found in the downtown San Antonio River last year, and dockless scooters are new items on the list of what workers pull out of the river.
From Monday through Thursday, around 110 crew members – just about everyone available from TCI’s stormwater division – will help clear sediment and debris from the channel’s muddy bottom, said Nefi Garza, the TCI’s assistant director who runs the division. They’ll use front-end loaders to scoop out buckets full of muck and haul it away in trucks.
“We have four days to do this work, so we have to get working really quickly,” Garza said at a press event Monday on the river’s Museum Reach.
With the river bed exposed, crews can remove the “dozens” of sunken scooters accumulated there, Garza said. They’ve also pulled out chairs, plastic Mardi Gras beads, and a prayer candle, Garza said. City workers will offer Bird, Lime, and other scooter operators a chance to pick up their merchandise, with everything else likely headed for the landfill, he said.
The practice of draining the river began in the 1980s, Garza said. Back then, the river’s eroding banks spilled enough sediment to the bottom of the channel to require an annual draining. The week of mud removal also came with an element of pageantry, with the yearly crowning of a new Mud King and Mud Queen. That tradition ended in 2010, according to the San Antonio River Walk Association.
Nowadays, the draining involves resetting the ecology of the urban river, where invasive species, including the apple snails, can easily out-compete natives.
City workers first spotted the snail in October near the City’s marina at Nueva Street, said Chris Vaughan, a River Authority biologist. The popular aquarium snail, native to South America, can grow to be fist-sized and drops distinctive pink egg sacs. On Halloween, River Authority crews removed 79 of these sacs to stop the snail from spreading. They gathered another 50 to 60 snails on Monday, he said.
Apple snails devour plants, Vaughan explained, and their presence can lead to a loss of food and fish habitat, throwing the river’s ecosystem out of whack. Home aquarium releases have led to the snails establishing themselves in parts of Texas as far back as the 1970s or 1980s, according to the Texas Parks and Wildlife Department.
The River Walk’s new snail population likely came from someone’s aquarium, Vaughn and fellow River Authority biologist Shaun Donovan said.
“You can get an apple snail from PetSmart or Petco,” Vaughn said. “I’m sure somebody bought one for their aquarium and it got too big or it ate all their aquarium plants and they dumped it into the river.”
The snails aren’t the only nonnative species that got to the river this way. River Authority crews also will be pulling out invasive tilapia, suckermouth catfish, and grass carp, they said. All were likely people’s pets until they were dumped in the river, they said.
“People buy a fish that’s small and they like it, and then it’s too big for their tank,” Donovan said.
In the drained channel, native species will be moved to still-flowing areas. The nonnatives are “culled” humanely after being brought to the City’s marina on Nueva Street, Vaughn said. Their remains are then put in a City landfill.
The river’s ecological balance is difficult to maintain naturally in the concrete-lined Museum Reach and downtown river channel, where it’s easy for nonnatives to have the upper hand, Donovan explained. Biologists see much less tilapia and suckermouth catfish south of downtown, where the natural habitat allows natives fish to compete more effectively.
“Once you start getting into the Mission Reach and a more natural area, our native species do a lot better job of competing against those because it’s the native species’ environment, whereas this is unnatural for everybody,” Donovan said.
Starting Thursday, TCI workers will begin refilling the river with water stored in the underground stormwater tunnel that runs below downtown. The water level should return to normal by Friday.