A 5,000-gallon tanker of drinking water stands ready to make its way to Austin. The city put out a boil water notice last week. Credit: Courtesy / San Antonio Water System

For almost a week, Austin, a city of 950,000 people, was without clean tap water as the city’s water utility struggled to recover from the effects of historic flooding on its treatment system.

A boil water notice was lifted Sunday afternoon, the Texas Tribune reported.

Like its neighbor to the northeast, San Antonio also experiences intense downpours. perhaps prompting San Antonio residents to wonder if the same thing could ever happen here.

Officials with the San Antonio Water System say no, for reasons both natural and man-made.

“No. 1, we’re predominantly a groundwater system,” said Jeff Haby, SAWS vice president of production and treatment. “So we don’t have surface water treatment plants. We don’t have to worry about the contaminants that come from surface water. The other blessing we have … is all the diversity of the water supply.”

San Antonio and Austin both grew up mostly depending on a single water source. In San Antonio, that source is the prolific Edwards Aquifer, a massive underground limestone rock layer.

In Austin, that source is the Colorado River, which flows from West Texas to the Gulf of Mexico.

All of Austin Water’s drinking water comes from two reservoirs on the Colorado River – Lake Travis and Lake Austin, both upriver from the city’s core. A series of dams and reservoirs along the Colorado River known as the Highland Lakes stores water during dry times and helps control flooding in rainy seasons.

Earlier this month, historic flooding on the Llano and Colorado rivers filled these reservoirs to the brim. Some floodgates were opened for the first time in years, sending torrents of water downstream.

All this water churned up silt, mud, and debris in the Colorado River, which made its way to Lake Travis and Lake Austin. It gummed up Austin’s three water treatment plants and slowed them down, Austin officials said on social media and in a series of briefings last week.

“It basically overwhelmed those systems because it was like chocolate milk,” said Haby, who participated in conference calls with Austin emergency management officials. “What it basically did was blind their filters, so they couldn’t process enough water. … They were using more water than they were producing.”

At the same time, the utility had to maintain enough pressure in its system to fight fires and prevent more contamination problems. That meant utility operators had to send water into the system that might have been contaminated with bacteria, such as E. coli or cryptosporidium.

On Oct. 22, customers were using approximately 120 million gallons per day, with treatment plants only able to supply 105 million gallons, Austin Water officials said on Twitter. They issued emergency water restrictions and said customers should begin boiling all drinking water to prevent illness.

“They really did it out of an abundance of precaution,” Haby said.

State regulators later imposed a mandatory boil water notice on Wednesday.

Austin Water officials did not return the Rivard Report’s requests for comment before deadline.

Haby said it’s rare for a city as large as Austin to have its entire drinking water supply affected, calling the situation a “worst nightmare” for water operators. SAWS has not encountered such a citywide situation in his 21 years there, he said.

SAWS CEO Robert Puente is interviewed by television media outlets. Photo by Scott Ball.
SAWS President and CEO Robert Puente. Credit: Scott Ball / San Antonio Report

“I can imagine the public outcry that’s going on in Austin right now,” SAWS President and CEO Robert Puente said. “I can imagine what restaurant owners are going through, coffee shop owners, car washes. … Everybody relies on water.”

To cope with the crisis, the City of Austin also banned all outdoor water use and mandated that water be used only for basic needs. By Tuesday, residents had cut their use enough so more clean water was going into the system than coming out during part of the day.

SAWS sent a 5,000-gallon tanker trunk to help deliver water to public distribution sites and places like the Travis County Correctional Complex and animal shelters. Mayor Ron Nirenberg said he asked Puente to assist after hearing from Austin Mayor Steve Adler on Monday.

In a phone interview Thursday, Nirenberg said he’s grateful that San Antonio has invested in diversifying its water sources to make the SAWS system more resilient.

“I think that the investments that we’ve made in capacity and conservation, technology, diversification, [and] redundancy all make water a strategic strength for San Antonio,” Nirenberg said, “which wasn’t always the case.”

Twenty years ago, SAWS got the vast majority of its water from the Edwards Aquifer. Because the water in the aquifer is so pure, SAWS doesn’t use water treatment plants to clean it. The utility adds a little chlorine for disinfection and fluoride for dental health before sending the water on to customers’ taps.

When flooding hits San Antonio, even over the Edwards Aquifer’s sensitive recharge zone, the aquifer and layers of plants, soil, and rock that lie on top of it help provide a natural buffer to pollution, Haby said.

The Edwards Aquifer Recharge Zone in Shavano Park.
The Edwards Aquifer Recharge Zone in Shavano Park. Credit: Bonnie Arbittier / San Antonio Report

However, parts of the Edwards Aquifer have become polluted. One example is a plume of chemicals tied to a dry-cleaning business contaminating part of the aquifer in Leon Valley. In May, the U.S. Environmental Protection Agency also put the spotlight on a former metal plating site that left pollution in the aquifer on the city’s far West Side.

But because there’s so much water in the aquifer and because SAWS has so many different wells spaced out across Bexar County, if one part of the aquifer became too contaminated, SAWS could pull water from other places to avoid a catastrophe, Haby said.

SAWS has also over the past two decades been steadily tapping into more and more water sources outside the Edwards Aquifer. The utility now is able to get some water from every major lake, river, and aquifer in the region.

SAWS can store more than half a year’s supply of water in its underground water bank, known as aquifer storage and recover, or ASR. The utility also turns brackish, or slightly salty, groundwater into clean drinking water at its H2Oaks facility in South Bexar County.

“There are just so many different sources now that we really are very redundant,” Haby said. “Plus, we have the wells all over town. … We can really move water around in a lot of different directions now.”

Though some neighborhoods and businesses in Austin have groundwater wells, Austin Water doesn’t draw any groundwater from the Barton Springs Edwards Aquifer. It’s the same rock formation as San Antonio’s Edwards Aquifer, but water mostly doesn’t flow between them.

Despite the city’s current water woes, Austin’s reliance on surface water instead of groundwater has its upsides. As the city has grown, it has managed to keep its iconic aquifer-fed Barton Springs flowing all year, even during droughts.

San Antonio’s growth, by contrast, quickly dried out the big urban springs in our area. For example, the Blue Hole spring at the headwaters of the San Antonio River once shot water into the air like a geyser, according to historical accounts. It now flows only during the rainiest times. It took the Sierra Club filing a lawsuit in the 1990s to stop San Antonio and its neighbors from drying out major springs in New Braunfels and San Marcos.

Austin appears to have no plans to start tapping the Barton Springs Edwards Aquifer, according to its draft Water Forward plan that discusses the city’s water strategies through 2115. The plan states that the Colorado River will remain Austin’s “core supply.”

However, the plan does call for some strategies San Antonio has already adopted, like ASR and brackish groundwater desalination.

Austin’s Water Forward innovative new conservation and reuse techniques, including creating incentives and requirements for large customers to start recycling and reusing more of their water on their own properties.

Austin also has more aggressive water conservation goals than San Antonio. It’s shooting for its customers to use only 83 gallons per person per day in 2070, compared to SAWS’ 88 gallons per person per day in 2070.

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Brendan Gibbons

Brendan Gibbons is a former senior reporter at the San Antonio Report. He is an environmental journalist for Oil & Gas Watch.