Lady Bird Lake has looked kind of junky lately. Here’s why.

It’s hard to think of a location more beloved to the people of Austin than Lady Bird Lake, often called the crown jewel of the city. Thousands of joggers, picnickers and kayakers flock to its shores every day to commune with the outdoors.

Lately, many of them have been saying the same thing: The lake looks like crap.

There’s been more stuff floating in the water than usual. Some of it is far away from shore where the current typically keeps the water clear. Closer in, plant life covers the surface in parts of the lake, so the water is hard to make out.

“As far as trash and debris, I would say people aren’t taking as good care of the lake as they have in the past,” Austinite GG Little said on a recent afternoon visit.

Visitors that day theorized the reasons include the annual Austin City Limits Festival, a nearby homeless encampment and “tourists.”

But the true answer is more complicated – and may not satisfy those who hope for a Lady Bird Lake with a surface of constant mirror-like clarity.

¡Hay cabomba!

The fact is that the recent abundance of litter in the lake is linked, in part, to the recent abundance of plant life, and both have to do with the weather.

“I’ve had quite a few calls this summer about, ‘What do we do about this?’” Brent Bellinger, a senior scientist with the Watershed Protection Department, said. “There’s not much we can do.”

Much of the vegetation people are seeing is a plant called cabomba, or fanwort. It is a native species that “waxes and wanes in its distribution,” Bellinger explains, but has proliferated in the lake recently because of long-term weather conditions.

“Generally, if we have a large flood event that moves through Lady Bird Lake, it’ll remove most of the aquatic biomass,” he said. “We haven’t really had that since the 2018 flood.”

That’s not necessarily a bad thing; the abundance of plant life is a sign of a healthy waterway.

“This isn’t a pool. It’s a natural ecosystem,” he said. “You want to have the plants versus the alternatives, [like] turbid water, algae.”

But in the absence of floods, something else happens: Trash and debris build up in creeks.

This year, specifically, Austin went months without any significant rainfall. The garbage kept piling up. Then came August, when a highly localized storm brought tides of water down Shoal Creek into the lake, along with the amassed litter and debris.

That storm caused “five years worth of stuff” to flow from the creek into the lake where it became “entangled in the mass of vegetation,” said John Beachy, a division manager with Watershed Protection who runs the city’s lake cleanup efforts.

“The trash got hung up in it,” he said. “We want to leave the vegetation and all the stuff that has the ecological benefits, but we need to get out all the Styrofoam and the plastic. And so you have to pick it all by hand.”

That’s exactly what crews have been doing, but it takes time.

“We have a crew of about five folks responsible for maintaining the 468 [acre] surface area,” he said.

The grass carp years

There are factors beyond droughts and floods at play in the current state of the lake.

For one thing, litter would be less of a problem if people simply picked up after themselves.

While he has not studied the issue, Beachy said, there also seems to be more plastic bags in the water since the Texas Supreme Court stuck down local bans on single-use plastic bags in 2018.

Another reason for increased lake vegetation could be the end of what Bellinger refers to as the “grass carp years.”

Back in 2012, Lake Austin, upstream from Lady Bird Lake, was plagued with an invasion of hydrilla, an invasive aquatic plant that covered the lake in thick mats of green.

To battle the hydrilla, the city turned to a natural predator: grass carp.

Austin released thousands of sterilized carp into the waterway to eat the hydrilla. The plan worked. But, after the hydrilla was consumed, the fish remained hungry and spread downstream.

“They went on to other plants,” Bellinger said.

The problem of grass carp eating native vegetation in the lakes became so serious that the city endorsed campaigns to remove the fish. While those efforts brought down grass carp numbers, the inevitable march of time is now finishing the job.

“Their lifespan is, in general, around nine years. The last [grass carp] stocking was in 2013,” he said. “So we’re kind of hitting or exceeding the general life cycle of these things.”

As the carp disappear, Bellinger has noticed a return of native plant species in Lake Austin along with a higher diversity of plant life in Lady Bird Lake.

“Ecologically,” he said, “it’s been really neat to see.”

And if you don’t like it, Bellinger said, cooler weather this fall will knock a lot of the plant life back and lead to less stuff floating in the water.

That’s something people who frequent the lake say they’ve already noticed is starting to happen.

This story was produced as part of the Austin Monitor’s reporting partnership with KUT.

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