The Downtown River Loop looks a bit different this week! The low water levels of the San Antonio River downtown are a result of intentional dewatering (river draining) of specific sections to conduct maintenance. During this brief dewatering event, which is expected to last about a week, maintenance and repairs will be made to structures that protect urban residents and visitors from flooding!
The affected areas are cooperatively operated and maintained by the City of San Antonio and the San Antonio River Authority (River Authority), and that same spirit of cooperation is on full display during these biennial draining events. During the river draining, the River Authority plays a vital role in monitoring and protecting aquatic life and water quality. This year, we are also working to prevent the spread of invasive animals as well!
How much water will be drained from the River Walk?
Around the horseshoe-shaped downtown loop that’s part of the world-famous River Walk, water depths vary but are typically less than 5 feet in many places, with deeper water in some areas. With the drop in water levels, this could leave 1-2 feet of water in some places and only a trickle through others. Animals like turtles, snakes, and crawfish will be able to seek refuge in spite of this change; however, the fish need some help!
What happens to the fish in the San Antonio River during draining?
Experts from the River Authority’s Environmental Sciences Department, led by our team of Aquatic Biologists, have been making sure no fish is stranded or left in an inhospitable environment! Staff have been monitoring since the water levels began dropping and will continue checking until the water levels are restored. These scientists are relocating native fish as necessary to areas that will provide sufficient warmth and oxygen.
What invasive species will be removed during the draining?
Invasive species present ongoing challenges in the San Antonio River, often outcompeting native plants and animals and disrupting the balance of the ecosystem. The river drain provides a valuable opportunity to address these challenges and take proactive steps to manage invasive species. When invasive species such as plecos (armored catfish) or Blue Tilapia are encountered, they are handled in accordance with state guidelines to help protect native species and maintain a healthy river ecosystem.
In an exciting step towards controlling the invasive Giant Apple Snail (Pomacea maculata), our scientists are taking advantage of low water levels to install an “exclusion device” in the fight against this invasive species. These snails degrade aquatic habitats and, in turn, decrease habitat and food sources needed by native aquatic species.
Our Aquatic Biologists have piloted different methods to prevent snails from laying eggs above the water surface. Each apple snail egg case can contain between 500 and 2000 eggs, so reducing their ability to reproduce is a big help in controlling their population! This week our Aquatic Biologists, with help from our Utilities team, are installing 800 feet of barrier in an area where some of the highest densities of apple snails have been recorded. We’re hoping this device will decrease the apple snail population, leading to fewer apple snails removed from the river, which you can monitor on our Apple Snail Removal Dashboard.
The team shows a section of the Apple Snail barrier they will install along the River.
What else do you usually find in the river during draining?
The River Authority also has staff from the Watershed and Park Operations (WPO) department to maintain infrastructure along the Museum Reach, like the Lock & Dam at Brooklyn Street. They are also taking advantage of these low water levels by removing litter before it gets carried further downstream!
In past years, there have been a multitude of items found and removed from the San Antonio River like e-scooters, chairs, plastic bottles, cans, clothes, etc. Some of these, namely the electronics, can leach harmful materials into the water, which in turn can harm the animals that live in and near the river.
River Authority WPO team members remove trash from the River.
The River Authority uses the river draining event as an opportunity to perform maintenance and repairs on river infrastructure.
How You Can Help!
If you feel inspired to protect our watershed through invasive species removal or litter pickup volunteer events, sign up to become a River Warrior! Email our engagement team at volunteer@sariverauthority.org or sign up through our volunteer portal. There, you will find all our upcoming volunteer events, announcements, and opportunities, including our aquatic biologist-led Apple Snail trainings starting in Spring 2026!
