Nowak was tapped for the job because of his success in the late 1990s with the Wisconsin Buffer Initiative, which brought farmers and environmentalists together to address the problem of agricultural runoff in the state’s waterways.

“The beginning of the process is just getting everybody to talk,” says Nowak, who expects the new initiative to be an even bigger challenge. “This is a hot situation. This is what social scientists would call rancorous conflict.”

To understand the recent history of irrigation in Wisconsin, one can start at Coloma Farms. Now a bountiful 2,700 acres of potatoes, soybeans and field corn, Coloma Farms began with just 80 acres in 1961, when the Diercks family established it as one of the first irrigated operations in the Central Sands.

To the Diercks family and most of those who grow crops on the region’s 200,000 acres of farmland, irrigation doesn’t just make their farms more productive; it’s an essential part of the business model. Sandy soils drain quickly. That’s an advantage for root crops because well-drained soils harbor less disease, but it also means they need frequent replenishment.

“Even if it rains two inches, you still only end up with three-quarters of an inch held in the topsoil, which is only about two days’ worth for potato plants during the summer,” says Andy Diercks BS’93, who co-owns the farm with his father, Steve. Full-season potatoes—the thirstiest of Coloma Farms’ crops—require between eight and 12 inches of irrigated water during a typical growing season.

Until recently, water wasn’t widely seen as a problem in the Central Sands. The region gets about 32 inches of precipitation in an average year, and it has a vast aquifer composed of sandy sediment permeated by water more than 100 feet deep in most areas. Rainfall and snowmelt continually recharge the aquifer, in stark contrast to the situation in the Great Plains, where extensive pumping for agriculture and other uses is steadily depleting the 174,000-square-mile Ogallala Aquifer. But clearly something has knocked the Central Sands hydrology out of balance.

And it’s not just dry lakes and streams. Beneath the surface, the water table has dropped to a worrying degree at a number of U.S. Geological Survey monitoring wells around the region. About eight miles north of Coloma Farms, the Hancock Agricultural Research Station’s well has dropped an unexpected three to five feet over the past 15 years. “From a pumping standpoint, that’s not a lot because the aquifer is so deep,” says soil science professor Bill Bland. “But it’s that top six feet of groundwater that feeds the area’s streams and maintains the lake levels, so it’s a big problem for people with lake cottages.”

Diercks is well aware of the surface water problems in the area, but he’s not willing to pin the blame on growers without more information. “The question is, what’s causing these problems? And how do we solve them, if we’re at fault?” he says. “If the scientists convince us that we’re the cause, then we’ll certainly be the first ones to line up to work out a solution.”

But figuring out what’s going on is a challenge. Scientists would like to compare the aquifer recharge that occurs on crop fields versus recharge on fields of native vegetation. Recharge, in turn, is affected by the amount of water that plants give off in the form of evaporation and transpiration, known together as evapotranspiration, or ET.

“You can think of evapotranspiration as a reverse, invisible rain. It’s happening all the time, but you can’t see it,” explains Bland. “If it doesn’t rain for two weeks, the native plants slow their water use—like they’re starting to go dormant—and there’s much less ET from the landscape they cover. However, our irrigated crops are always evapotranspiring water at the rate the atmosphere will accept it,” transferring, in essence, water from the aquifer to the atmosphere, where it blows away.

Unfortunately, it’s difficult to quantify ET and recharge in the field, so scientists often turn to computer models and other methods for answers. Using a computer model, Bland found that stands of prairie do a better job recharging the aquifer than forests and irrigated field corn. A statistical analysis, performed by Kung, shows that ET has increased significantly across the entire western part of the Great Lakes region over the past 15 years—evidence, he believes, that climate change could be a factor in the Central Sands’ water situation. “It’s like nature is taking away more from us across the whole landscape,” says Kung. “It’s like an invisible hand is stealing our water.”

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Tags: A.J. Bussan, Andy Diercks, Brian Wolf, Central Sands, Central Sands Water Initiative, Coloma Farms, Dan Trudell, Environment, evapotranspiration, George Kraft, Grow Spring 2012, Irrigation, lakes, Long Lake, Nicole Miller, Peter Nowak, potatoes, Sam Kung, streams, Vanishing Waters, Water, Waushara County, Wisconsin Potato and Vegetable Growers, WPVGA
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