Solving Water Supply Issues

San Antonio’s water source diversification has made it secure for future generations

Solving Water Supply Issues

Paige and Accuosti work in the lab at the Aqua Vista Plant.

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A $930 million, 142-mile-long pipeline has further diversified San Antonio’s water portfolio and has decreased the fast-growing city’s reliance on its major water source — the Edwards aquifer — by nearly 20% during the last two years.

The Vista Ridge pipeline draws 50,000 acre feet of water annually — or 16.2 billion gallons — via 18 wells drilled into the Carrizo and Simsboro aquifers, about 90 miles east of Austin in Burleson County.

Thanks to that supplemental supply, the amount of water drawn from the Edwards aquifer in 2022 (nearly 147,000 acre feet) dropped to 53% of the city’s total water needs, down from 66% in 2019, the year before the Vista Ridge project went online, says Robert Puente, president and chief executive officer of the city-owned San Antonio Water System.

“The Vista Ridge project was not only the biggest capital-improvement project in our utility’s history, but in the history of San Antonio too,” notes Puente. “In fact, it’s the largest water project in the United States at a total cost of $2.9 billion — all of it from private-sector investment.”

The pipeline project, combined with a robust water-conservation outreach program and other water-portfolio diversification efforts, earned SAWS a Sustainable Water Utility Management Award from the Association of Metropolitan Water Agencies in 2022.

Over the last two decades, the 31-year-old utility has built a desalination plant, developed an aquifer storage-and-recovery system and created a water-recycling system, all aimed at easing dependence on the Edwards aquifer — and minimizing the potentially adverse impacts of climate change on local water supplies.

The efforts have paid off. In 1995, the Edwards aquifer supplied 100% of the city’s water. Today, SAWS manages 15 water-supply projects that draw from nine different sources.

For further perspective, consider that in 2022, SAWS delivered 277,122 acre feet of potable water to customers. Of that, the Edwards aquifer contributed about 53%, Vista Ridge generated roughly 15%, other aquifers produced more than 9% and the utility’s H2Oaks Aquifer Storage-and-Recovery facility produced 4.5%. The remainder was supplied by desalination of brackish aquifer water and other minor surface water sources, according to SAWS statistics.

“Water essentially isn’t an issue here anymore,” Puente says.

Spurred by endangered species

San Antonio was prompted to diversify its water sources after the Sierra Club filed a lawsuit in 1991, alleging that over-pumping in the Edwards aquifer was reducing the flow of two area springs, which subsequently threatened eight endangered species, including two kinds of salamanders, a crustacean and two kinds of fish.

In 1993, a federal judge agreed. That eventually led to the state legislature imposing restrictions on how much water the city could pump from the aquifer: 234,000 acre feet per year.

“The main risk of doing nothing to make our water supply sustainable was losing major industries,” Puente says, noting that two large companies threatened to move unless the city found a sufficient and stable source of water.

Years in the making, the Vista Ridge project was funded and built by a consortium of private companies that negotiated leases for water rights with more than 3,400 landowners in Burleson County.

“In Texas, if you own land, you also own the water under it,” Puente explains. “It’s called the rule of capture.”

The Carrizo and Simsboro aquifers are a good water source because their immense size renders them drought-resistant.

“We basically told water marketers out there to figure out how to deliver 50,000 acre feet of water a year to our doorstep and we’ll pay for it,” he explains. The total cost for SAWS: about $100 million a year, which comes to around $3 billion over 30 years.

Low-risk contract

The cost of the water — $1,606 per acre-foot — doesn’t increase during the life of the contract. And after that, another 30-year water contract with the landowners kicks in, but this time at a lower price, Puente says.

Furthermore, after the initial 30-year contract expires, SAWS assumes ownership of the Vista Ridge infrastructure, with the loan note presumably paid off by the consortium at that point.

While it’s fairly common for ownership of assets in public-private projects to revert back to a utility after a specified time period, the Vista Ridge agreement is unusual because the consortium — not SAWS — assumed the financial risks associated with building the pipeline as well as other potential liabilities.

For instance, if a groundwater district (an agency composed of appointed or elected officials that regulate local water supplies) reduces or eliminates water production, SAWS isn’t contractually obligated to pay for water it no longer receives. So the consortium takes a financial hit, not SAWS.

“What is unprecedented in this agreement is the extraordinary risk shifted away from a public entity onto the private consortium,” Puente says. "Our only risk is that regardless of whether we have a wet year or not, we have to pay for 50,000 acre feet of water every year.”

The main components of the Vista Ridge project are the pipeline and wells, three pumping stations and improvements to Agua Vista Station, the terminus of the pipeline, which features two 10-million-gallon-capacity water tanks.

One tank is owned by the developers and is used for storage while the second tank is used for the city’s water distribution. A treatment plant between the two tanks ensures that water from the Carrizo and Simsboro aquifers matches water from the Edmunds aquifer so customers don’t notice any difference.

Recycled water provides a boost

To further reduce dependence on the Edwards aquifer, SAWS established a water-recycling system that went online in 1996. Today, more than 130 miles of pipelines deliver highly treated effluent to more than 80 customers, including industrial and commercial businesses, golf courses, municipal parks, military and healthcare facilities and other entities.

“It’s the largest direct recycled-water system in the nation,” Puente says. “All the water that goes down drains — from sinks, commodes, showers and so forth — makes its way to one of our three sewage treatment plants.”

The system can recycle up to 125,000 acre feet of water a year, which conserves a large amount of potable water. In 2022, the program generated about 56,200 acre feet of recycled water; about 42,400 acre feet was used by a local electric utility to help generate power and another 7,600 acre feet was distributed to around 80 business customers.

The remaining 6,200 acre feet was discharged into the San Antonio River to maintain sufficient water flow. This is particularly important for the city’s River Walk, an extremely popular tourist attraction that features numerous shops, restaurants, museums, artisan markets and more, all located along 3.5 miles of walkways that line both sides of the river.

More portfolio diversification

SAWS also minimizes aquifer dependence with a $213 million desalination plant that went online in 2017 and the aforementioned ASR system that began operating in 2004. Both systems are controlled by operators in the H2Oaks Center in far southern Bexar County.

At the center, 11 wells pump around 12,000 acre feet of salty, brackish water a year from the Wilcox aquifer, which then is treated via reverse-osmosis membranes and distributed to customers.

“The desalination plant is designed to accommodate three phases,” Puente says. “The second phase, which would add another 12,000 acre feet of capacity, is built except for some wells that need to be drilled, so we can accommodate future growth relatively quickly.”

The center also controls the ASR system, which Puente says is the largest system of its kind in the United States. Water pumped from the Edwards aquifer is carried by a 20-mile-long pipeline to 29 injection wells, where it’s deposited into the Carrizo aquifer, which lies in between the Edwards aquifer and the Wilcox aquifer.

“We pay for the 234,000 acre feet of Edmunds aquifer water we’re allotted each year, whether we pump it out or not,” he explains. “So we pump as much as we can and whatever we don’t sell to customers, we store in this underground reservoir in the Carrizo aquifer.

“It’s hard to say how much we store on an annual basis because it all depends on whether it’s a drought year or a wet year,” Puente adds. “In rainy years, we take out as much as we can.”

At the end of 2022, the ASR reservoir held an estimated 189,000 acre feet of water, enough to supply about nine to 10 months of drinking water for San Antonio. In 2022, it distributed 14,900 acre feet of water while taking in 11,600 acre feet, according to SAWS data.

Furthermore, the ASR system worked exactly as designed during the area’s record-breaking drought from 2011 through 2014, enabling SAWS officials to maintain the city’s water supply without imposing severe water-use restrictions. In all, 50,000 acre feet of ARS water was distributed during the drought, utility statistics show.

Mission accomplished

A former member of the Texas House of Representatives and a pioneer in establishing best practices for water supply management statewide, Puente was appointed to his current position in 2008. As such, he’s seen firsthand many of the changes to San Antonio’s water portfolio and views the utility’s accomplishments with great pride — especially since they were achieved during a time of rapid population growth in San Antonio.

“We run a top-notch utility with one of the lowest water rates in Texas,” he says. “I can very confidently tell our community that we now are water secure for future generations to come.”


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