Hydrilla continues to spread in Lake Austin

AUSTIN, Texas - The city says there has been a spike in hydrilla growth since last summer, and with warmer months ahead, it could become a big concern for people who want to head to Lake Austin.

The backstory:

"It's all across Lake Austin right now, as in from dam to dam, and it has progressively gotten worse," said Tara Carr, general manager of Lake Austin Marina.

Hydrilla has quickly spread across Lake Austin since last summer. The city says last month it spanned nearly 600 acres, up from about 450 in the fall.

"Went from something 50–60 acres to a few hundred acres in the winter, and it's kind of remained that you know four or five, you know, plus a hundred acres over the winter," said Dr. Brent Bellinger with the Austin Watershed Protection Department.

Hydrilla is a nonnative, invasive plant which serves as an important part of aquatic ecosystems.

Dr. Brett Bellinger with the Austin Watershed Protection Department says hydrilla still can have positive benefits, like improving fish and water quality and absorbing nutrients.

"It's habitat for aquatic organisms, everything from the bugs to the fish, but then it's also feeding wading birds and other waterfowl that people like to observe and are important parts of the ecosystem. So, it provides a lot of ecosystem services on the positive side," said Bellinger.

But it can also create problems.

"Because this plant grows on the surface and keeps growing, you get these, you know, thick kinds of topped-out mats and rafts at the water surface that then, you know, really kind of start to impair recreational uses," said Bellinger.

What they're saying:

At Lake Austin Marina, some business owners say they've already seen the impact.

"When you have a novice boat driver who is trying to navigate around a fishing boat, and they are also pulling someone behind them on a tube and then seeing hydrilla on the other side of them, it can create a really dangerous situation," said Carr.

And with temperatures rising, she worries the problem could get worse.

"The temperatures warm up, we'll see it bloom a whole lot more," said Carr.

Carr worries if conditions don’t improve, people could avoid the lake all together.

"I do expect that if it doesn't actually get better or people feel as though it's being managed, that it will impact a lot of businesses here at Lake Austin," said Carr. 

Bellinger says the city is working to get the situation under control.

"We're really trying to bring the situation back under control with these dynamic climatic factors that are really interacting in novel ways and challenging ways to manage this reservoir," said 

In November, officials released nearly 2,000 sterile grass carp into the lake, fish that feed on hydrilla, but it’s still a waiting game.

"These are critters that feed over a long period of time. And so, it takes a while to really start to see their impact on the system. But that said, given that we haven't seen those reductions that we were hoping for," said Bellinger.

The city says it’s continuing to explore additional options, including possibly adding more grass carp this spring or lowering water levels in the fall.