Experts: Rock County's groundwater both plentiful, vulnerable

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Anna Marie Lux
Sunday, March 23, 2014

ROCK COUNTY--The coldest winter in memory may have raised awareness about the tap water so many take for granted.

After home and business pipes froze in communities across Rock County, municipal officials instructed many residents and businesses to run water continuously for weeks or even months to prevent pipes from freezing again.

The waste of so much water got people wondering:

How does the groundwater that we depend on for slaking thirst, watering crops and taking showers get there? Is it an endless supply? How vulnerable is it to pollution?

Truth is, when it comes to water, Rock County is spoiled.

“You can drill a well almost anywhere in Rock County and hit water,” said hydrogeologist Kenneth Bradbury. “You have a fantastic supply of water.”

Bradbury has made a career of studying the ways that groundwater moves through the soil and rock of the Earth.

He works with the Wisconsin Geological & Natural History Survey, which is part of the University of Wisconsin-Extension.

“Some of the highest producing wells in Wisconsin are along the Rock River,” Bradbury said.

The reason is the area's geologic history. At the end of the last glacial period, melting ice deposited huge amounts of porous sand and gravel along the ancient river valley. Many of the county's 13,000 to 15,000 private wells and some of the 50 municipal wells tap into this thick layer of water-rich sediment, usually at depths from 50 feet to 150 feet.

The depth of the sand-and-gravel aquifer varies from being nonexistent to more than 200 feet.

About 20 percent of the county's private wells reach into the limestone aquifer, typically located beneath the sand-and-gravel layer. Municipal wells tend to get water from a combination of both shallow and deep wells. The deepest wells tap into the sandstone aquifer, typically found beneath the sand-and-gravel and limestone layers.  

Rock County depends on these underground aquifers for all of its water. The numbers show that usage is up. From 1979 to 2005, total water use in the county increased from about 27.2 million gallons per day to about 45.4 million gallons per day. The rise was due to increases in domestic and irrigation uses, a state website reports.

“We each use at least 50 gallons of water a day,” said Tim Banwell, Rock County environmental health director. “We're very blessed to have all this water, and we take for granted a resource that other communities do not have.”

Fewer than 50 miles from Janesville, the city of Waukesha is searching for a new water supply. Up north in Taylor and Shawano counties, communities are drilling deep into the ancient bedrock for the liquid treasure. Out west, from California to Colorado to Wyoming, the well has long gone dry.

In Rock County, we literally walk on water. But how much do we have?

“It depends,” said Rick Wietersen, groundwater program manager of the Rock County Health Department. “We have large quantities of water in the sand-and-gravel aquifer. However, there are concerns about pumping from the deeper sandstone part of the aquifer.”

 Some Wisconsin communities have experienced problems.

“We've seen examples of where the deeper aquifer is drawn down in Green Bay, Madison and Waukesha,” Wietersen said. “We have not seen it in Rock County, but we are not monitoring it closely, either.”

The deeper sandstone aquifer is not as water rich as the shallow sand-and-gravel aquifer, but it has better water quality.

“Due to issues with nitrates or bacteria problems, many people and municipalities are replacing shallow wells with deeper wells, which are placing a demand on the sandstone aquifer,” Wietersen said.

The U.S. Geological Survey and its partners run a network of more than 100 monitoring wells to keep track of groundwater levels in the state.

None are in Rock County.

In addition to the deep aquifer, more demand is being placed on the shallow sand-and-gravel aquifer. In recent years, more farms and industries have tapped into it by installing high-capacity wells, which can pump 100,000 gallons or more water daily.

“The sand-and-gravel aquifer is generally abundant,” Wietersen said, “but it is being drawn on by more and more irrigation wells between Janesville and Beloit. As they increase, we want to keep a close eye on even the abundant aquifer.”

Kathy Mooney of the state Department of Natural Resources said Rock County has more than 200 high-capacity wells, which the agency regulates. The wells can be in both shallow and deep aquifers.

“The department looks for impact on surface waters and the geology of the area,” she said. “We will determine if one can be constructed, where and to what specifications.”

Since 2010, the department has approved 32 new high-capacity wells in Rock County.

From 2000 to 2009, the department approved 37 high-capacity wells.

That compares to 32 in the 1990s, 31 in the 1980s and 50 in the 1970s, when the technology was new.

After the drought of 2012, “we were inundated with high-capacity well applications,” said Mooney, who is with the Drinking Water and Groundwater Bureau. “In times of dry weather, usually more wells are constructed.”

High-capacity wells help boost yields in dry or drought conditions.

DNR staff said farmers also install high-capacity wells because:

-- Higher grain prices give them more money to be able to install irrigation systems.

-- Dairy farmers want to grow their own feed to avoid having to pay high-grain prices.

-- Banks may require irrigation systems on farming loans to help ensure against crop failure and bankruptcy.

-- They want to move from surface-water irrigation systems to groundwater systems for better quality and quantity of water.

For comparison, Walworth County has 127 high-capacity wells; Jefferson County 94 and Dane County 222.

In the Central Sands region of Wisconsin, the numbers are much higher. Portage County has 821, Adams 514 and Waushara 510.

Environmental groups, citizens and others in the Central Sands region say the growing demand for high-capacity wells from agriculture and other sources has harmed streams and lakes.

Charles Dunning wants people to think of groundwater and surface water as a single resource. He is a hydrogeologist with the Wisconsin Water Science Center of the U.S. Geological Survey, an agency of the U.S. Department of the Interior.

“If you pump a large volume of groundwater, you will likely have a measurable effect on the surface water,” he said. “More and more, we are concerned about the ecological health of local streams and wetlands. You can't think compartmentally about the two. The whole system works together.”


Both Dunning and Bradbury say it is a myth that groundwater migrates hundreds of miles from where it soaks into the earth. Instead, groundwater typically reaches its point of discharge at a river, lake or wetland within a few miles from where it entered the ground. Sometimes, it is less than a mile.

The idea that groundwater doesn't travel far is a powerful one, Bradbury said.

“It means that what you do in your county can greatly influence your groundwater, both in quantity and quality,” he said.

Pollution released into groundwater travels in the direction of the groundwater and is likely to stay within the county's boundaries, except where it is discharged into and carried out of the county by surface water, he explained.

Much of Rock County's water comes from shallow aquifers, generally less than 250 feet, which are the most susceptible to pollution.

“Anything happening on the surface will more quickly affect the sand and gravel aquifer,” Dunning said. “It is about as vulnerable as it gets because there is less filtering from the surface.”

In shallow aquifers, pollution issues tend to be human-made and include contamination from farm chemicals and animal waste, farm and urban fertilizers, road salt and leaking underground storage tanks.

Contrary to popular belief, groundwater does not occur in a huge underground river.

Instead, Rock County's groundwater depends on local rain and snow for replenishment. When rain falls or snow melts, some runs off directly to streams. Much evaporates or is taken up by plants, depending on the time of year. The rest infiltrates into the ground.

Under the influence of gravity, rain or melting snow seeps through the soil and sand and gravel sediments to the water table.

Of the 30-plus inches of rain that has traditionally fallen annually, an average of about 6 inches recharges the groundwater system in the Rock River Basin.

“Recharge occurs nearly everywhere, unless it's an area covered by buildings or pavement,” Dunning said, explaining that things such as soil type, slope and vegetative cover affect how much water soaks into the earth.

In wet years such as 2007 to 2010, the water table rose several feet to record-high levels. The opposite happened after the drought of 2012.

For many people, groundwater is out of sight. But Bradbury said it should not be out of mind.

“What is more important than your groundwater?” he asked. “People in Rock County need to be proud. They are living in a place with a great water resource. But they need to be stewards of it. They need to think about where it comes from and where it goes.”


In Janesville alone, residents used 3.6 billion gallons of water last year.

David Botts, director of the city's water utility, said the amount is probably normal for the city's size.

Since General Motors shut down most of its operation in December 2008, Janesville's water consumption has decreased.

In 2003, the city used 4.9 billion gallons.

“Between businesses and our residential usage, people are more aware of the cost for water,” Botts said. “Everyone is trying to reduce their operating costs and be more conservative.”

The city has eight wells, which vary from 100 feet to 1,200 feet deep. The biggest water producers are the shallowest ones.

“Water availability in the Rock River Basin is quite good,” Botts said. “We see no issues with availability in the future. But that doesn't give us license to use more than we need.”

The city offers rebates for people to install toilets, sinks and shower heads that reduce water use.

Frost this winter has penetrated to 5 feet deep, where service laterals provide water to homes and businesses.

“The frost is still very deep,” Botts said. “We still have 470 customers running water to make sure their pipes don't freeze. It definitely will show that we used more water this winter than in other years.”

As the year progresses, the city will look at how to eliminate some of the frozen water-pipe issues.

“The winter has created problems we have not had to deal with in a long time,” Botts said. “You don't realize how important water is until you turn on the faucet and nothing comes out.”





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