Second of four stories from Tucson.

A golf course in the desert is a surreal sight - lush, emerald fairways, giant palm trees, ponds of aqua-blue water surrounded by sun-beaten, dry rock and sand.

"People come to the desert and they expect to see sand dunes and things, this is a little oasis right in the middle of town, and just a beautiful setting for golf," said Wade Dunagan, who manages this city's five city golf courses.

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It also might seem like an absurd waste of precious water in a city that lately is lucky to receive 10 inches of rain a year. But the water that feeds Tucson's golf courses isn't pumped out of the ground or taken from a river.

It's treated sewage water.

Over the past several decades, Tucson has slashed its per capita water consumption by more than a third, and one of the more startling ways it's done that is by reusing water after it's flushed down the toilet or run through a washing machine. At times, residents have acted on their own, even illegally, to use practices that have since become standard.

Tucson's water recycling steps stand out, even in comparison with other Arizona cities, like Phoenix, and they represent actions that some in Minnesota say residents need to think harder about.

"It's the right thing to do," Dunagan said. "It really is a necessity and we like being part of that program."

"We may not go to the extremes of people in the Southwest and California, but still, we need to start thinking about a different future than what we used to."

Tucson first delivered recycled water to a golf course in 1980. Since then it has laid 160 miles of special purple pipes that funnel as much as 30 million gallons of treated wastewater per day to golf courses, schools, parks and about 700 homes.

That saves enough water to serve 60,000 families, said Tucson Water spokesman Fernando Molina.

Tucson Water's public information officer Fernando Molina explains how purple pipes at the Clearwater Recharge and Recovery Facility indicate the use of reclaimed water. Nick Cote for MPR News

"Every gallon of recycled water or reclaimed water that we can use for irrigation is a gallon of drinking water we're preserving," Molina said.

"It's the right thing to do. It really is a necessity and we like being part of that program."

The idea he says is to match the right quality of water for the right use. You don't need drinking quality water, for example, to irrigate a golf course.

That's a water ethic that Ali Elhassan, water supply manager with the Metropolitan Council, said needs to take root in Minnesota, where in many places groundwater withdrawals are outstripping the rate of recharge. That's a hard notion to swallow in a state with abundant surface water.

The sun bakes the dry bed of the Santa Cruz river in Tucson, where a proposed project will try to revive the river. The once mighty river was the lifeblood of the region for early settlers of Tucson but dried up as the population grew. Nick Cote for MPR News

"This is one of the toughest challenges for many of the water supply managers around the metro area and around the state," Elhassan said. "How to convince people to conserve water, how to convince people to reuse, reduce the amount of water they're using." In Tucson, water reuse starts at the county wastewater plant. Tucson takes water that has been treated in the plant and runs it through giant filters to purify it but not to standards required for drinking water. Then it sends it out through a network of purple pipes to distinguish it from the blue pipes that carry drinking water.

And water the utility doesn't need right now, it stores underground.

Excess treated wastewater is sent across the street from the city's water treatment plant, to a park called Sweetwater Wetlands. It filters through an artificial wetland and then is allowed to soak into the underground aquifer that the city can tap later.

The city does the same thing with water it gets via canals connected to the Colorado River hundreds of miles west of here. Tucson uses only a third of the 144,000 acre feet it has a right to (an acre foot is the amount of water it takes to cover an acre to a depth of one foot - about 325,000 gallons.)

It pumps the rest into 40-acre basins, big turqouise rectangles that shimmer in the hazy desert sun. The water slowly filters into an underground aquifer, and then the city pumps out only what it needs.

"Every gallon of recycled water or reclaimed water that we can use for irrigation is a gallon of drinking water we're preserving."

Between reclaimed wastewater and the Colorado River, Tucson derives about 90 percent of the 34 billion gallons of water it uses in a year from sources other than groundwater.

As a result, Molina said, aquifer levels that had dropped more than 200 feet are climbing back up.

Tucson Water has made one of their water treatment facilities, Sweetwater Wetlands, into a public park and urban wildlife habitat. Nick Cote for MPR News

"We've seen the water level rise 50 feet, and that's just from natural recharge, and that's in drought, too."

How Tucson reuses water:

--Delivers 30 million gallons a day of treated wastewater to golf courses, parks, schools and homes.

--Stores most of the water it gets from the Colorado River underground.

--Pays residents to capture rainwater for use on lawns.

--Encourages residents to store wastewater at their homes, using it later for lawns and other uses, something that once was illegal.

Many homeowners throughout Tucson are beginning to do the same thing with rainwater.

They store it in big cisterns when it pours down during the rainy seasons, then use it to water landscaping during long dry spells. Tucson Water offers $2,000 rebates to homeowners, and the city now requires commercial developments to use rainwater for at least half their irrigation.

Homeowners are also harvesting water from inside their homes.

Val Little sits in the backyard of her home in Tucson. Little is the director of the Water Conservation Alliance of Southern Arizona, a group that aims to educate the public about water conservation practices. Nick Cote for MPR News

"This is my illegal kitchen greywater setup," Tucson resident Val Little said as she showed off a little valve under her kitchen sink. If her leftover dishwater is pretty clean, she turns the valve one way so she can send the water out to water her grapefruit tree.

But if it has grease in it, she flips it back the other way and it drains to the sewer.

Technically, it's still illegal to reuse kitchen water, because regulators worry residents will discharge dirty water.

But that's not a concern with the water from her shower and washing machine. She helped change the law 10 years ago as director of the Water Conservation Alliance of Southern Arizona. She says she first conducted a survey to show how many people were already using greywater.

"This is my illegal kitchen greywater setup."

"We discovered about 13 percent of folks in southern Arizona were lawbreakers and proud of it."

With that data in hand, Little said, the Arizona Department of Environmental Quality changed its regulations. Now Tucson even requires new houses to be plumbed for greywater, a step that Minnesota regulators are far from taking.

A similar kind of guerrilla conservation has happened with stormwater. Residents began cutting holes in street curbs to allow water to rush off the pavement and on to street-side landscaping. After seeing how well it worked, Tucson last year passed one of the first "green infrastructure" ordinances. Now new road construction projects are required to capture their stormwater.

All these initiatives are designed to reduce Tucson's reliance on groundwater. Would Minnesota ever need to go to such lengths to capture and reuse water?

"We may not go to the extremes of people in the Southwest and California, but still, we need to start thinking about a different future than what we used to," said Elhassan, who formerly helped manage water supplies in California and New Mexico.

Although there are a few wastewater reuse projects in Minnesota, more interest has focused on capturing and using stormwater.

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Elhassan said less frequent but more intense rainfall predicted with climate change will reduce groundwater recharge and increase storm runoff. As a result rainwater and stormwater reuse will likely need to play more important roles in Minnesota, but it will be expensive to build the infrastructure, he said.

"Cost is going to be one of the challenges," Elhassan said. "We need to learn about how to do this the right way. It's a new area. We have to build our knowledge about that."

Educating the public is critical to start developing a conservation ethic around groundwater that rivals Minnesotans' value for our lakes and rivers, he said.

But that's not easy to do, said Sharon Megdal, who directs the Water Resources Research Center at the University of Arizona.

"That's one of the challenges with groundwater, is you can't see those declining levels" she said. "You look at boat ramps suddenly being stranded, that's a visible sign, but with groundwater you don't have those visible signs."