David Johns jumps into Barton Springs Pool, but not for play. He gets right down to business testing the water's oxygen levels. Johns is the city's hydrogeologist.
Tuesday, he measured the milligrams per liter of oxygen in the water at 6.5. That means oxygen levels are normal and water flow in the Edwards Aquifer is high. It sounds promising, but Johns says he's seen better.
"Over time, there has been a trend of there being less dissolved oxygen in the water at similar flow conditions, say, less now than there was, say 30 to 40 years ago under similar conditions,” Johns said.
So, what's eating the oxygen? Johns blames the drought drying up the water flow, the lack of rainfall and the city's growth.
"With increasing urbanization in the area that feeds Barton Springs, there's more dissolved material and/or organic material that may be getting in the aquifer, and that organic material can consume oxygen,” he said.
If that keeps up, it can be catastrophic for Barton Springs' two endangered residents, the Barton Springs Salamander and the Austin Blind Salamander.
"They are our canary in the aquifer. They are the perfect indicator of whether the aquifer is healthy. When they start to suffer, we know the water is suffering,” Bill Bunch with the Save Our Springs Alliance said.
Johns says the salamanders are like humans.
“If they're not breathing really well, they're not getting enough oxygen, they're not going to be eating, they're not going to be reproducing and therefore, it's a strain on their population,” he said.
Johns says trying to keep oxygen levels ideal is like swimming against the tide.
"There's not a whole lot we can do about that,” he said.
For now, they're just watching the levels closely, making sure Barton Springs remains safe for even the smallest swimmers.
The last time Barton Springs' oxygen dropped to critical levels was in 2013. The city had to install bubbling tanks to keep the water flowing and oxygenated.
The Watershed Protection Department will keep testing the waters every two weeks.