Hydrilla in Lake Austin Under Control

October 31, 2013by Brian Talley

OLYMPUS DIGITAL CAMERAThe City of Austin is reporting that hydrilla within Lake Austin is under control, and during a Texas Parks and Wildlife Department vegetation survey, the aggressive, invasive plant was entirely undetected within the prized central Texas waters.

Since 1999, the proliferation of hydrilla has caused problems for homeowners and leisure users of Lake Austin, with dense growth impacting flood flows, water intakes, and recreational activities. In February of 2013, hydrilla reached its historic high concentration of 600 acres, helped by drought-induced low water flows and warmer water temperatures, both of which are favorable to the plant.

A science-based stocking plan of sterile Asian grass carp, which target hydrilla as their main food source, is credited for the successful control of the plant.

The September study revealed that, along with a decline in hydrilla coverage, Eurasian watermilfoil, a less aggressive exotic plant, expanded to about 200 acres. Milfoil provides critical benefits to the reservoir’s health, such as serving as an aquatic habitat for fish and other wildlife and helping to maintain water quality and fishing opportunities. Three months prior to this survey, 135 acres of milfoil and 330 acres of hydrilla were found.

While hydrilla was not detected in the survey, the City cautions it is probably not eradicated, as it likely will re-sprout from underground tubers and grow stronger from an eventually declining grass carp population. Water flow and temperature changes also may impact future growth rates.

The City and TPWD are continuing to monitor Lake Austin vegetation and state they will continue to consider all lake user interests when determining the best courses of action for control efforts and for native aquatic vegetation establishment projects, which are conducted by the City of Austin’s Watershed Protection Department to boost the natural ecosystem.

To read more about the issue of hydrilla in Lake Austin, visit www.austintexas.gov/department/hydrilla.