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image of hand pump in an old farmyard.

Gauging Groundwater

Water-rich Minnesota cannot afford to take its underground water supply for granted.

By Brian DeVore

Well driller Earl Drussell's family has been poking and prodding the rock, sand, and soil of southeastern Minnesota's valleys and ridges for more than a century. Drussell extracts drinking water out of dark places hundreds of feet below the taps. His clients rely on this subterranean substance for survival. It's the most basic thing imaginable, but like many basics, water is often taken for granted.

"The only time people worry about conserving water is when they don't have it," says Drussell.

Minnesota has always been associated with water in lakes, streams, and rivers. Yet one aquifer alone, the Mount Simon, as deep as 1,000 feet below ground, stores trillions of gallons of water within its sandstone -- enough to swamp the entire state to a depth of 5 feet. Ground water, which creeps between cracks, through sand, and over rocks beneath the land's surface, is the source of a significant percent of the base flow for surface-water systems. Without ground water, Minnesota would have no cold-water trout streams, and most wetlands and rivers would dry up during dry spells.

While half the nation's population drinks ground water, more than 70 percent of Minnesotans get their drinking water from underground. Around 1.25 million Minnesotans draw water from private wells. Between 10,000 and 12,000 new wells are drilled every year. Most of that well water is drunk straight from the ground. Even municipal well water is often treated only with fluoride.

Despite our reliance on this source, "we know very little about ground water," says Bob Merritt, area hydrologist for the Department of Natural Resources in northwestern Minnesota. "We know a whole lot more about our lakes and streams, and that makes sense because we can see them."

In recent years ground water has drawn national attention because of contaminated supplies and aquifers that stay depleted after being pumped. "The label of Minnesota as water rich does not fit as well as once believed," conclude the authors of Use of Minnesota's Renewable Water Resources: Moving Toward Sustainability, a report issued last April by the Minnesota Environmental Quality Board and the DNR. The report, which analyzed recent trends in water use and projected future needs, makes one thing clear: Minnesotans can no longer afford to ignore the comings and goings of underground water.

Today, Minnesotans are using more water per capita. Industrial uses such as ethanol production are putting new demands on aquifers. Development is stressing aquifers too, especially on hot summer days when homeowners turn on lawn sprinklers and crank up air conditioning -- causing peak electrical demand from power plants, which likewise use large amounts of surface water. All these demands for water -- plus land-use changes that pave miles of impervious surfaces, and possibly climate change -- are disrupting the recharge cycle that is key to the sustainable use of ground water.

Biggest Users

Water use can vary depending on the weather, but the overall trend is that households, businesses, factories, and farms are using more water. Between 1995 and 2005, statewide water demand for all purposes rose 18 percent, while population grew 12 percent.

By 2030 the state's population is expected to increase by 26 percent. Demands on ground water will also increase.

Power generation, by far the biggest user of water in the state, used approximately 853 billion gallons of water in 2006 to cool equipment. Almost all of it comes from surface-water sources, which is considered "nonconsumptive" use because 98 percent of the water goes back into the waterway. In contrast, almost all groundwater use is considered "consumptive" because it is pumped from an aquifer but returned to surface water or allowed to evaporate. Though the water remains in the environment, it is lost from the local aquifer.

Water use by municipalities, industrial processing, and irrigation runs a distant second, third, and fourth, respectively. These water users draw from ground water as well as surface water.

Large water consumers (those that pump more than 10,000 gallons in a single day or 1 million gallons a year) are required to have a permit and pay an annual fee to the DNR for the processing of their water-use data. The DNR has a good idea of how much water is being used because it issues permits to public water suppliers, irrigators, factories, and other industrial water users.

"Minnesota's water appropriation permit program began in 1937, and it is one of the best in the country," says Kent Lokkesmoe, DNR Waters director. "Improvements in our regulatory program and knowledge of the resource will continue to improve. The DNR has a statutory responsibility to ensure an adequate water supply to meet long-range seasonal requirements."

Saving ground water at home, on the farm, and in industry

Water-efficient appliances, as well as low-flow showers and toilets can pay off -- reducing household water consumption to 49.6 gallons a day from the typical 72.5 gallons per day, according to the American Water Works Association.

Fix leaks: A leaky faucet dripping at a rate of one drop per second will waste around 2,700 gallons per year.

Small rain gardens -- shallow depressions planted with water-tolerant native vegetation -- can help recharge ground water when placed in strategic locations to capture runoff from drain spouts, parking lots, and other impervious surfaces. They also filter pollutants. See "Gardens for a Rainy Day," May-June 2004.

Parking lots and driveways can be made more permeable by using pervious paving stones and gaps in the pavement planted with grass or other vegetation.

Find tips for saving water in and around your home at H2O USE and Metropolitan Council Water Conservation Toolbox.

Well-structured soils conserve moisture, improve recharge, and help keep contaminants out of ground water and surface water. Manure, composts, and cover crops can improve soil structure.

A U.S. Department of Agriculture study found that across a range of soil types, from clay loam to loamy sand, the soil's available water content increased 10 to 20 percent when land managers reduced tillage or added another crop such as oats to a corn-soybean rotation. For more information contact the Minnesota Institute for Sustainable Agriculture

Unused wells can be a direct conduit for contaminants into aquifers. Visit Minnesota Department of Health well-sealing information, or call 800-383-9808.

The Minnesota Technical Assistance Program works with businesses to prevent pollution and increase efficient use of ground water. With its help, one food-processing company cut annual water use by 13 million gallons -- saving $400,000 a year. Learn more from MTAP on how your business can cut water consumption or call 612-624-1300 or 800-247-0015.


Variable Supply and Demand

Minnesota's aquifers range in size from spits of sand a few square miles in size to vast sponges -- underground layers of porous ancient sediments -- that cover more than 1,000 square miles of underground real estate. Overall, the aquifers are holding their own in terms of quantity, says Laurel Reeves, DNR Waters appropriation permit manager. But like politics, all ground water is local. "When it comes to water in the state, it's location, location, location," says Reeves. "Water is not distributed evenly."

Southeastern and east-central Minnesota are considered groundwater rich. The western part of the state is not. Northern Minnesota's supply is a mixed picture (see page 22).

Within regions, groundwater availability can vary considerably. For example, in northwestern Minnesota, water availability changes dramatically within a 50-mile stretch starting in the Red River valley (poor) and heading east (good). Likewise, in southwestern Minnesota, well drillers can hit plentiful water in one spot and come up dry less than a quarter-mile away.

Hydrologists worry most about increased water demands where groundwater stores are low or relatively unavailable because of geology. For example, the Interstate-94 corridor between Minneapolis and St. Cloud may be headed for an aquatic train wreck, says Dale Setterholm, associate director of the Minnesota Geological Survey. Almost every county along this stretch is projected to grow at least 5 percent annually through 2010. The corridor runs over the Anoka Sand Plain, where shallow sand-and-gravel aquifers are vulnerable to contamination from nitrogen fertilizers leaching from farm fields and lawns. Poorly functioning septic systems also produce nitrate pollution. The number and quality of aquifers diminishes as one travels west on Interstate 94. Around St. Cloud, the crystalline bedrock is a very poor aquifer.

Moorhead's water demands became so great a decade ago that it began blending surface-water and groundwater supplies. Before the 1990s Moorhead was getting all of its water from the Buffalo aquifer. Then DNR observation wells began showing that the city was drawing the aquifer to dangerously low water levels. As a result, in 1994 Moorhead began to also take water from the Red River of the North. Surface water requires much more treatment to make it potable. But by drawing from both ground water and surface water, Moorhead was able to reduce the strain on both resources.

More Pumping

Minnesota gets 90 percent of its irrigation water from underground. In 1988, a drought year, 102 billion gallons of water were pumped to irrigate row crops, wild rice, landscaped areas, nurseries, orchards, cemeteries, and golf courses, according to data assembled by DNR Waters hydrologist Sean Hunt. In 2006, another drought year, 116 billion gallons of water were pumped for irrigation. The number of irrigation permits issued and the acreage covered both increased by more than 45 percent from 1988 to 2006. Irrigation water use for commercial landscaping more than tripled; irrigation demand for corn and other major crops increased 10 percent.

It's not surprising that a growing population and a demand for more consistent watering of plants have put increased pressures on ground water. But perhaps the fastest growing user of ground water in the state -- ethanol plants -- has caught a lot of people off guard.

"We weren't ready for it," concedes Dave Leuthe, regional hydrologist for DNR Waters in New Ulm. "It kind of landed on the landscape out here, and people didn't give water availability a thought."

As of 2007, Minnesota had 17 ethanol facilities. Six more facilities are being built, and 11 more are on the drawing board, according to the Minnesota Pollution Control Agency. On average, such plants use 4 gallons to 5 gallons of water for each gallon of ethanol produced. During the past decade, as ethanol production in Minnesota has skyrocketed, the industry's overall volume of water use has increased more than 250 percent, according to information compiled by the DNR and published in a report by the nonprofit Institute for Agriculture and Trade Policy.

Most new Minnesota plants are targeted for the western part of the state: an area rich in corn but poor in water. Residents near Granite Falls learned that the hard way when an ethanol plant went into operation there in 2005.

"Every time I went for a drive, it seems they were digging a new well for the ethanol plant," recalls Jerry Ostensoe, who lives within a quarter-mile of the plant. The facility had initially been given a temporary, three-year permit by the DNR because of concerns about drawing down the aquifer. But less than a year after it went into operation, the local aquifer dropped precipitously and water levels in wells up to eight miles away were dropping in response to the pumping.

"We saw 50 feet of drawdown. People were starting to run out of water in areas where they didn't have problems before," says Leuthe.

In February 2007 the plant switched to the Minnesota River as its source of water. It has used recycling technologies to reduce water consumption by 1 gallon per gallon of ethanol produced. Plant owners also paid to have new wells drilled for Ostensoe and a handful of other landowners.

Both the Institute for Agriculture and Trade Policy and the National Academy of Science have issued reports expressing alarm at the impact biofuels production could have on ground water. Because of such concerns, the DNR has increased the period a test well must be pumped from seven days to 30 days during the permit application process. "Even that only provides a 30-day window of water use," says Leuthe. "You can try to predict, but things can happen after that."

Groundwater Vintage

Earl Drussell says he can still find plenty of water, but he and other well drillers are increasingly forced to go deeper to find aquifers that contain older, potable water. The age of ground water ranges widely. Some shallow aquifers hold yesterday's rain, while others are deep reservoirs of prehistoric precipitation. The wide variance in vintage is important: Newer water in shallower unconfined aquifers tends to be more affected by the human environment, while older water from deeper, confined aquifers is usually unspoiled by modern civilization.

Hydrologists have found that chemicals, antibiotics, and other contaminants may persist for a long time in the cool, dark conditions below ground. Thousands of Twin Cities area residents, from Edina to New Brighton to Woodbury, are learning this as testing increasingly shows their water has been tainted by solvents, petroleum residues, and chemical compounds that are legacies of an era of unenlightened waste disposal.

The town of Lewiston in southeastern Minnesota has drinking water so contaminated with nitrogen from farms, golf courses, lawns, and septic systems that it has to blend its regular well water with water from a well that taps a deeper aquifer. The cost of removing nitrate from public water supplies can be high -- more than $1.40 per 1,000 gallons in southeastern Minnesota. Boiling water can remove bacterial contamination, but it will further concentrate chemical pollutants. Reverse osmosis can purify water, but the process uses much water and produces concentrated hazardous byproducts that require special disposal.

Nature's underground filtering systems remain the most effective and inexpensive water purifier.

"Literally all of the water we drink falls on the ground first," says Setterholm. "We kind of depend on these magic processes to clean it up underground."

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