FOUNTAIN, Minn. - This tiny town 30 miles south of Rochester is the place to come to see why southeastern Minnesota's water supply is both the most plentiful in the state but also the most vulnerable.
Known as the Sinkhole Capital of the nation, it marks the location of Fountain Big Spring, flowing at the base of a steep valley just outside town. The stream runs all year and never freezes, and forms the headwaters of one of the many trout streams in the area.
"This spring comes out of a small cave," said Department of Natural Resources hydrologist Jeff Green, "and it is connected by groundwater, by conduits, by openings in the limestone, to the sinkholes up in Fountain."
From here, the water moves quickly down vertical cracks to horizontal layers underground. Green estimates that water seen at Fountain Big Spring will take just a week to be deep underground, recharging the Prairie du Chien aquifer that many cities tap for drinking water.
"That line blurs and groundwater becomes surface water and vice versa literally overnight," Green told Minnesota Public Radio (http://bit.ly/1g5x03h ). "The soils are thin ... so everything's very interconnected and things move very fast compared to the rest of Minnesota where groundwater does not move miles per day like it does here."
Fast-moving water in southeast Minnesota, a region of rolling hills and caves, bluffs and valleys and hundreds of miles of freshwater trout streams, helps create an abundant groundwater supply. In some areas, it's just 10 to 20 feet below the surface.
That's a good thing for the 11 counties that get all of their drinking water from the ground, instead of rivers or lakes. But it also means nitrate contamination from fertilizer applied by area farmers happens fast in the aquifers closest to the surface.
As a result, some communities are being forced to take steps - sometimes costly ones - to both tap and protect their groundwater.
Concern over nitrate contamination of surface and groundwater is widespread, said James Lundy, a hydrogeologist for the water protection unit of the Minnesota Department of Health.
"It tends to be present when other things more expensive to measure are present," Lundy said. "So it's kind of a canary. It's kind of a way to vaguely know more than we ought to know just from measuring nitrate."
There are tens of thousands of wells across this region. About two-thirds of the residents drink water from wells installed before the state adopted its well code in 1974.
In 2008 and 2009, more than 500 of those wells were sampled, and approximately 10 percent had nitrate concentrations that exceeded the safe drinking water levels.
High nitrate levels in water can cause blue baby syndrome, a condition that can reduce oxygen supply and result in brain damage or infant death.
"That's why when we find high nitrate, we drill deeper to get away from it, which sometimes heads us into arsenic or radium problems or other problems," Lundy said. "But at least we get away from the nitrate."
Getting away from nitrates is what the city of Lewiston, a town of 1,600 residents between Rochester and Winona, set out to do 14 years ago.
The city's oldest working well, drilled about 400 feet into the ground in the 1970s, is high in nitrates.
So in 2000, the city built another well, 1,100 feet down into a deeper aquifer. But that brought another problem.
The new water contained naturally occurring radium. Long-term exposure to radium can cause diseases such as lymphoma and bone cancer.
Other cities nearby - Red Wing, La Crescent, Rushford, Winona and Goodview - also tap aquifers with radium, and they have built facilities to treat the water, according to Paul Halvorson, district engineer in the Minnesota Department of Health's drinking water protection division.
But for a town Lewiston's size, that's expensive. A treatment facility and a new well would cost $3.1 million and double water rates for residents. An average 5,000-gallon-a-month user currently pays $28 per month for water in Lewiston; treating the water would increase those bills to $56. Lewiston's population has remained relatively steady in the last decade, but the city lost several big businesses, including a yearbook-manufacturing plant that employed 300 workers and the bowling alley, and without that tax base, city officials say they don't know where they'd get the money to pay for the facility.
So the city is drilling a new well for $1 million, hoping it can find clean water that makes a new treatment facility unnecessary, said City Clerk Jen Hengel.
"We wanted to take, not a step back necessarily, but just pause and look at what other alternatives may be out there," Hengel said. "We started to look at other aquifers in this area that would potentially be a source of drinking water but not have the radium and not have the nitrates."
But some Lewiston residents say a water treatment plant would give them peace of mind they don't have now.
About five years ago, Richard and Karen Ahrens, a couple in their 60s, stopped drinking tap water in Lewiston because they are concerned about health risks.
"It's a scary thought," Richard Ahrens said, "if you're drinking a cancer-causing agent."
The two are retired farmers and lifelong Lewiston residents. They pay about $30 a month for bottled water, in addition to about $22 for their city water bill.
Like many Lewiston residents, Richard Ahrens wants the city to build the filtration plant. But as a former council member, he understands the financial burden it would place on the city - and his neighbors.
"Some people could handle it, some people couldn't," he said. "And that's the problem. You've got to look at the big picture. A lot of people have trouble paying water bills. This economy isn't helping things any. We've got to put our money in the gas tank, not in the water bottle. It's a hard situation."
While Lewiston struggles to find clean water and the money to pay for it, just down the road in Rochester, the situation is different.
Rochester's population has doubled since 1970 and stands at more than 107,000. Forecasts predict another 32,000 residents in 20 years. Housing developments have marched into former farm fields as the city annexed 10,000 acres since 2000.
Rochester's groundwater supply is clean and abundant. But as the city grows, so does the need for more water. The city has 32 municipal wells and the capacity to add up to 20 more in the future.
Unlike larger Minnesota cities, it uses no water from rivers or lakes and thus pumps more groundwater than any other city in the state - 12 million gallons a day.
Rochester Public Utilities is working with the U.S. Geological Survey and a private engineering firm to anticipate long-term sustainability questions.
"This is kind of a state-of-the-art model that can help us predict, as we add wells, as our pumping levels increase, as our population increases and as we're using more water out of the Jordan aquifer, how that will impact it," said Todd Osweiler, the utility's environmental and regulatory affairs coordinator.
One outcome is that the city is taking steps to encourage residents to conserve water.
Rochester's per capita water use has dropped from 60 gallons a day in 2004 to 53 gallons last year, according to the utility's historical water demand data.
Osweiler said the long-term impact of the city's population growth is hard to predict. He doesn't foresee the city having to tap the nearby Zumbro River as an alternative water source. But in a part of Minnesota where the land is so sensitive, he said all options are on the table.