But much of the focus in the three cities rests on conservation and reuse. El Paso Water, which is partially dependent on the uncertain flow of the Rio Grande River for its drinking water, developed a pilot plant to treat sewage with microfiltration, reverse osmosis, ultraviolet light and carbon filtration. The process is capable of quickly putting treated wastewater back into the drinking supply within hours. The city is building a full-scale $78 million treatment plant, the first of its kind in North America, to clean up and supply 10 million gallons a day of drinking water.

El Paso has long experience with state-of-the-art treatment plants capable of meeting that demand. In 2007 it opened the largest inland desalination plant in the world to remove salt and treat brackish groundwater to drinking water standards. The plant produces 27.5 million gallons of water a day.

San Antonio, which supplies 175 million gallons of drinking water a day, is intently interested in interacting with its customers to instill a stronger water conservation ethic in the city. It’s much less expensive than building new treatment plants and water pipelines. The Vista Ridge pipeline adds $12 a month to the average water bill, according to city figures.

The water sensor program that San Antonio introduced in December 2018 has attracted 5,000 users, said Ric Miles, the chief operating officer of Flume, Inc., the manufacturer. The device tracks home water use in real time, and has the capability of sending alerts about potential leaks. Flume is readying newer devices that can distinguish water use for outdoor watering systems or indoor flushing, showering, and laundry. The device will be capable of delivering a pie chart showing how much water is used for specific activities. “The idea is to give people more information,” said Miles. “Being more informed could lead to altered consumption patterns. If you don’t know anything you won’t change anything.

Austin Water focuses on an approach to managing water supply that is holistic and long-term. The idea is to treat all facets of supply, demand, and use as interconnected. A drop of water collected from an air conditioning system can be directed to irrigate the building’s garden or recycled to flush toilets, or treated to drink from a faucet. Water collected from rooftops can be collected and stored in on-site water tanks for almost any use that is recyclable and treatable.

The Texas Living Waters Project, a collaboration between the Sierra Club, the National Wildlife Federation, and the Galveston Bay Foundation calls the approach “One Water.” The result in Austin is a municipal system designed to waste less water, be more resilient to drought, and not anxious to reach outside its geographic water basin for new supplies.

The city is ambitious in pursuit of its One Water goals. Austin, for example, requires developers to engineer their projects to capture stormwater and rainwater for reuse and recycling. It’s encouraging construction of pocket treatment plants that could eventually replace the centralized, energy-intensive water treatment systems that now are dependent on big pipes and pumps.

Decentralized equipment reduces construction and maintenance costs for handling and treating water. It also limits costs for pumping, which typically are a city’s largest electrical expense. Last year El Paso Water, which serves 200,000 less people than Astin, spent $12 million running its water pumps and equipment.

“We have more opportunity now to do things at the building level,” said Kevin Critendon, assistant director of Austin Water, which serves 1 million people in the capital region. “There’s no one silver bullet. To be prepared for an uncertain future we need to develop a number of strategies for supply, and for demand.”

Austin Water has two intrepid innovations to make the point. The city’s six-story, $125 million, 200,000 square-foot Central Library opened in October 2017 to rave reviews for its One Water array of water collection, recycling, and reuse innovations. The library’s design team, brought together from multiple conservation and engineering disciplines, produced a building that collects rooftop rainwater and water dripping from air conditioning systems and directs it to an onsite cistern that holds 373,000 gallons. Water stored there is piped to an onsite pocket treatment plant that recycles it to irrigate the building’s landscaping and gardens, and for flushing toilets and urinals.

The other example is the city’s 260,000 square-foot, $250 million Planning and Development Center, which goes several One Water steps further. The building, scheduled to open this year, is designed with two onsite water recycling systems. The first is a $1.7 million “blackwater reuse” system that collects wastewater from the building’s toilets and sewer drains. It treats the wastewater in a 5,000 gallon per day new technology pocket plant that uses membranes, aeration and a biofilter to replace conventional bacteria-based aerobic wastewater treatment. The treated water will be used in a recycling loop to go back into the building to flush toilets and urinals.

The second system at the Planning Center collects rainwater, stores it in a 40,000 gallon cistern, and uses the recycled water for irrigation at an installation cost of $625,000. The utility said both systems are designed to supply about 42,000 gallons of recycled water daily or 84 percent of the building’s demand.

The city will collect data about its effectiveness. If it works well, Austin Water will promote the installation of similar decentralized systems in buildings and in business districts.

For water consumers in all three cities, innovation provides protection in the event of a severe drought. Just as important, the three cities deliver water at competitive prices. Brett Walton, Circle of Blue’s Seattle-based correspondent, prepares an annual report on the cost of water in 30 U.S. cities, among them Austin and San Antonio. In 2016, Walton prepared a graphic that showed the average monthly bill for the 30 cities. Austin and San Antonio were in the middle of the pack. Water in Austin cost more than in Memphis, a Mississippi River shoreline city, but considerably lower than Las Vegas and other big western cities.