Brazos River Basin Under Siege: Invasives Threaten Local Ecosystems

Zebra Mussels
Zebra Mussels

There's a group in town that is not exactly the kind you want to invite to your garden party.

They spread fast, and it's hard to stop them.

Invasive animals and plants may at first seem harmless, but they are pesky critters that can quickly become a nightmare for native species, ecosystems, and even humans. From zebra mussels clogging up water pipelines to kudzu vines smothering landscapes and waterways, invasive species are a growing threat that demands our attention.

Across the Brazos River basin, they are stealing water and hindering recreation.

As they continue to spread at an alarming rate, the question remains: what can we do to stop them before it's too late? The first step is to recognize them.

Invasive animals

Once non-native species are introduced to an area, they have few natural predators, competitors, or diseases to keep them from spreading like wildfire.

Often unintentionally, invasive species are spread by human activities. Boats may carry them on their propellers or in livewells, plants can escape into the wild or some invasive species are intentionally or accidentally released pets.

Unfortunately, prevention, detection, monitoring and repairing the damage caused by invasive species is extremely expensive. The nationwide annual economic impact of invasive species on the state exceeds $120 billion, according to the Texas Parks and Wildlife Department. Fishing and hunting opportunities, property values, water recreation, and water quality can all be impacted by invasive species.

Three particular animals rank among the most common invasive animals in Texas and the Brazos River basin: zebra mussels, feral hogs and nutria.

Zebra Mussels

They are the size of a dime but have caused alarming declines in native mussel species and can disrupt a water supply system by colonizing the insides of pipelines and restricting water flow, according to TexasInvasives.org, a partnership of state and federal agencies, conservation organizations, green industry, academia and other private and public stakeholders. Millions of dollars are spent each year controlling, cleaning and monitoring zebra mussels in other states, according to TexasInvasives.org.

As of August 2022, 30 Texas lakes across five river basins are infested with zebra mussels, which means the water body has an established reproducing population. The infested lakes within the Brazos River basin include lakes Georgetown, Granger, and Stillhouse Hollow. Once these mussels clog intake pipes at our water supply reservoirs, the cost to repair and replace infrastructure is passed on to each of us through increases in our water bills.

The TPWD and partners monitor for invasive mussels in Texas lakes, but anyone who finds them in lakes where they haven't been found before or who spots them on boats, trailers or equipment is encouraged to help identify and prevent new introductions by immediately reporting the sighting to TPWD at (512) 389-4848 or by emailing photos and location information to aquaticinvasives@tpwd.texas.gov.

Visiting a lake soon? There are easy steps to make sure your watercraft 'doesn't transfer zebra mussels.

  • Clean: Inspect your watercraft, trailer and gear. Remove all plant material and mud.
  • Drain: Remove all water from the boat, as well as the motor, bilge, live wells and bait buckets.
  • Dry: Open all compartments and allow the boat and trailer to dry for at least a week or more before going into another body of water. If the boat cannot be dried for a week, it is recommended that the boat be washed with high-pressure and soapy water.


Often mistaken for a beaver, nutria weigh up to 22 pounds and live up to 10 years. They can swim underwater and are agile on land. With large front teeth that are often yellow or brown, nutria are, in fact, a large form of rodent.

The animals with yellow or orange teeth have a relatively high reproductive rate. Combined with a lack of population controls, nutria have resulted in an explosion of the species, according to the Texas A&M AgriLife Extension Office.

Due to their large appetites, nutria have damaged agricultural crops and infrastructure. Homeowners living near Texas waterways report damage and destruction to trees and landscaping. But most importantly, nutria carry several pathogens and parasites that can be transmitted to humans, livestock and pets, according to the U.S. Fish and Wildlife Service.

There are measures you can take to manage the invasive animal if they venture onto your property. The Texas A&M AgriLife Extension Office has information here.

Feral Hogs
Feral Hogs

Feral Hogs

If you know them, 'there's a good chance you already dislike them.

Feral hogs negatively impact agriculture by trampling, consuming, and digging up massive amounts of planted crops. These same activities also degrade riparian ecosystems leading to increased erosion, runoff, and bacterial loading from fecal material, leading to significant degradation of water quality.They are extremely destructive.

In the United States, they number more than 6 million and are found in at least 38 states or territories, according to the U.S. Fish and Wildlife Service. Currently, they are found in every Texas county, except El Paso, according to TexasInvasives.org.

Feral hogs are well known for destroying lawns and landscaping in a very short time, costing thousands in repairs. To help defend your property from feral hogs, report sightings to TexasInvasives.org through an online reporting tool.

Invasive plants

Invasive plants can take over and harm the environment. They can grow quickly, crowding out and taking over native plants.

The most common invasive plants include alligatorweed, Chinese Tallow Tree, hydrilla, giant reed, giant salvinia, kudzu, saltcedar and water hyacinth.

The most economical and safest way to manage invasive species is to stop their growth before they become established. The best way to do that is by identifying the plant and preventing its spread. Recognizing plants will allow you to remove them at the root or treat them with the proper herbicides to prevent their spread.

Chinese Tallow Tree

  • With tremendous reproductive potential, it can produce an average of 100,000 seeds annually.
  • Nearly impossible to eliminate once established.
  • Mainly placed for its unique ornamental qualities, including colorful, autumnal foliage.



  • Kills or degrades other plants by smothering them under a solid blanket of leaves.
  • Thought to have been brought into the state to help stabilize erosion along riverbanks or as a decorative garden plant.
  • Capable of growing at an alarming rate of up to 1 foot a day.


  • Earned its name because it oozes salt from its leaves.
  • Can consume large quantities of water, reducing the amount of water available for other plants, animals and humans.
  • Can have pale pink or white flowers and fruit, they have long tap roots that allow them to intercept deep water tables and interfere with natural aquatic systems.


  • Forms thick mats that crowd out native aquatic vegetation, reduce water flow, lower dissolved oxygen levels, and increase sedimentation.
  • Can cause flooding by impeding drainage and restricting water flow for irrigation.
  • Spreads rapidly and is difficult to remove.



  • Named after Hydra, the nine-headed serpent of Greek mythology.
  • Can grow an entirely new plant from a tiny stem fragment.
  • Dense mats of Hydrilla can alter water chemistry, cause dramatic swings in dissolved oxygen levels, increase water temperatures and affect the diversity and abundance of fish populations.

Giant Reed (Spanish reed)

  • Thought to be native to Eastern Asia
  • Brought to the US in the 1800s to be used for erosion control
  • This plant crowds out native plant species, contributes to higher fire frequency and intensity and modifies river hydrology.

Giant salvinia

  • A floating fern from Brazil.
  • Can damage aquatic ecosystems by outgrowing and replacing native plants that provide food and habitat for native animals and waterfowl.
  • Infestations can double in about a week under the right circumstances.

Water hyacinth

  • Floats on water and can spread from small fragments and seed production.
  • Can produce thousands of seeds a year that can be viable for up to 30 years.
  • Thick layers of hyacinth could also interfere with boat navigation and recreational activities.

Important: Never treat water-based invasives yourself. Proper use of herbicides for treating invasives in drinking water must be applied by a licensed professional.

Identifying and stopping the spread of invasive plants early will save you money and a great deal of work on your lawn and landscape.

If you're a boater, help stop the spread of invasives in our reservoirs by always:

  • Cleaning mud or plant fragments from the boat, propeller, boat trailer and all gear, including waders and boots, before leaving a water body.
  • Draining all the water from the boat, including the bilge, live well, motor, and trailer, tackle and gear before leaving the area.
  • Drying the boat trailer and gear after each use.
  • And never release aquarium or water garden plants into the wild. Instead, seal them in a plastic bag and throw them in the trash.

"Nationwide, the annual economic impact of all invasive species in the U.S. has reached approximately $219 billion, with global impacts estimated at over $4 trillion," according to the TPWD in an April 2021 release. "Aquatic invasive species are among the worst of these, requiring considerable effort to prevent, monitor for, and effectively manage and mitigate infestations when possible. In response to this need, for the past five years — since the state's fiscal year 2016 — the Texas Legislature has allocated approximately $3.2 million annually to combat aquatic invasive species in Texas."

The Brazos River Authority's environmental services department regularly monitors different plants as a way of tracking the health of the Brazos River basin ecosystem. When the results show changes, the BRA along with state and federal partners, works to identify the cause. Once a cause is identified, work can be done to improve the continued health and quality of the basin's water supply.

Learn more about species in the Brazos River basin here.