* Correction appended

Last week, on a quiet residential street in north-central Austin, a crew in hard hats and yellow safety vests worked to dig up a water pipe that had been laid in 1951. The pipe was prone to leaking, and the Austin Water Utility had decided to replace a long stretch of it as part of a five-year, $125 million push to replace leaking pipes.

"Instead of continuing the Band-Aids, we just do the whole line," said Jason Hill, an Austin Water Utility spokesman. Last year, the utility lost 8.6 percent of its treated water to leaks — a good rate, Hill said, for a city of Austin's size.

As Texas recovers from the severe drought of the last two years, water experts say that conservation is the easiest way to ensure that the state will have enough of water for future growth. Fixing leaks is one method that took on added importance since the drought caused pipes to crack as soils dried out and shifted. But homeowners and businesses also have plenty of room to cut back on water use, especially on lawns, which account for at least half of the average home's summertime water demand. Farmers, who account for 60 percent of the overall state's water use, can also save more, though their share is already declining as cities grow.

The need to conserve was driven home by the 2012 state water plan, which opens with the statement: "In serious drought conditions, Texas does not and will not have enough water to meet the needs of its people, its businesses, and its agricultural enterprises."

"Conservation is an essential part of the state water plan," says John Nielsen-Gammon, the state climatologist. "It's part of how we get from point A to point B. It's also the least expensive to implement."

The push toward conservation is gathering pace, especially in cities. This spring, Dallas — a heavy water user, with about 120,000 gallons per year on average for a single-family household last year — announced that it was implementing permanent watering restrictions, limiting homeowners to two days of watering per week. Austin is also considering enacting permanent restrictions — something that El Paso, the driest major city in Texas, has had in place for a few decades.

"I think the best water management practice is to always restrict the use of outdoor watering," state Rep. Lyle Larson, R-San Antonio, said at a committee hearing this spring, in the wake of a visit to El Paso.

But enacting restrictions can be wrenching, especially in places that pride themselves on small government. Both Midland and Odessa — both of them in the perpetually dry Permian Basin — put in place restrictions for the first time last year, amid the worsening drought. "We don’t respond really well to, ‘Okay, the government says you’ve got to do this, and by God you’re going to do it or we’re going to string you up,’” Midland Mayor Wes Perry said last year, as he explained Midland's initial preference for voluntary restrictions (which did not work).

Restrictions — especially temporary ones — don't always translate into cutbacks. Last year water use rose in a number of Texas cities, even as they tightened restrictions. That's because the drought prompted people to water more than usual to save their lawns. It's a conundrum for the state that in times of drought, when water is especially precious, people want to put more on their lawns or fields.

Raising water rates, especially on high users, is another tool, though it's not popular and can cause political headaches for city officials. Some cities, including the town of Fair Oaks Ranch, north of San Antonio, have enacted special surcharges to be applied when drought strikes, according to Jennifer Walker, a water resources specialist with the Lone Star Chapter of the Sierra Club.

Some cities, including El Paso and San Antonio — both of which have significantly slashed per-capita water use, by 30 percent over 20 years in El Paso's case and more than one-third in 15 years in San Antonio's — have also at times given away free water-saving appliances like low-flow showerheads or toilets, or at least offered rebates.

However, "the key is targeting outdoor water use," said Ron Kaiser, a professor of water law and policy at Texas A&M University.

Kaiser is overseeing some interesting research in College Station. There, researchers at Texas A&M have identified the top 10 percent of outdoor water users — roughly 2,000 people — and have been testing ways to persuade them to bring usage down, presumably because it triggers the human emotion of guilt. Just telling them they are in the top 10 percent — an easy first step — can trigger reductions.

"If you just notify folks, sometimes you'll see a reduction of 5 to 6 percent," Kaiser said.

Another measure Kaiser is taking involves suggesting to homeowners how much they should be using based on the square footage of their yards. That allows them to understand whether they had leaks or an especially inefficient system. The assumption, he said, was that some of the big water users were unlikely to tear up their lawns (especially since College Station's rates on top water users are not terribly high).

"We had a number of people in College Station who said, 'We have big yards, so we're always going to use more water,'" Kaiser said, adding that the city offered free water checkups to participants, and gave those who came in under average an "atta boy" statement of approval.

Not everyone was excited about the research, Kaiser acknowledges. "Some people were indignant," he said, and others said they had large families. Another issue, he said, was backsliding: Whereas people may be excited to cut back on water use initially, that excitement may wear off over time.

The Legislature could do more to encourage conservation, experts say. For example, it could provide incentives for agricultural users to switch from older, less efficient water systems to new, water-saving ones. "You might get your biggest bang for your buck there," said Tom Mason, a water lawyer with Graves, Dougherty, Hearon & Moody in Austin, who noted, however, that this would go against the general budget-tightening drive. The state could also require cities to price their water at increasing tiers, so that bigger users had to pay more — something that most big cities in Texas do, but not all towns.

The state could also, Mason said, do more to simply promote public education on conservation. In neighboring Oklahoma, after all, last month the governor signed a bill that establishes a statewide goal of using no more water in 2060 than the state uses now. The Texas agriculture commissioner, Todd Staples, has a new initiative that encourages landscaping conservation.

But funding a far-reaching statewide conservation effort, Mason said, would be "a huge first step."

This is the last in a four-part series on water use in Texas. Part One discussed cities increasing water rates. Part Two was on the push toward desalination. And Part Three was about the rush for reclaimed water.

Editor's note: An earlier version of this article incorrectly stated that a Dallas single-family household used 120,000 gallons per month last year. The text has been corrected to say that the figure is about 120,000 gallons per year.