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​Volume 31 No. 1 Winter 2006


When Ice Shoves

It got cold early that year. I remember hearing eerily warping, moaning sounds traveling down the lake during a still and subzero night. The sound fit into the same category with the extraordinary sounds of loons and sandhill cranes. The lake was making ice.

Formation of an extraordinary substance

Ice on our Wisconsin lakes provides us with many things: beauty, recreation and a chance to "walk on water." The trouble comes when the ice leaves the lake and comes on land.
The formation and movement of the ice cover is complicated and many variables affect the quality, thickness and actions of ice.

With the coming of cold air temperatures, water at the top of the lake cools and becomes denser. Warmer water will normally rise and colder, denser water will sink. Here is the amazing thing about water…as it becomes colder from the point of 39.2 degrees Fahrenheit (�F), it becomes less dense and expands. Ice forms when water molecules reach 32 �F. Because it’s now less dense than surrounding liquid water, ice rises. You can see this happen in a pitcher of water as the ice cubes float at the surface. Imagine if ice was less dense and did not float -- lakes would freeze from the bottom up and fish or animals would be unable to live.

By the time water reaches the freezing point, its volume has increased by about 1/8. That’s why pipes burst when they freeze. Water also expands slightly again as it warms, but contracts when it gets very cold. The power of freezing and thawing water is great enough to split granite and is a force that brings down mountains and changes the earth over the eons.
On cold nights when a lake surface is not disturbed, needle-like crystals start to form. The crystals unite and continue to grow. If all goes well, a clear sheet of ice will form. Once the surface is covered by ice, direct heat lost from the water is limited and the ice sheet will gradually thicken.

Ice shoving

While ice eventually contracts with an appreciable drop in temperature, a warming temperature causes ice to expand slightly. For example, if the temperature increases from 14 to 32 �F, a lake one mile across can expand laterally about 32 inches, with forces exerted outward as much as 30,000 pounds per square inch. The ice cover on a lake is a floating mass, except at the points where it freezes tightly to anything it touches such as the shore, a bridge abutment or a pier. When ice warms it pushes outward against the things to which it is attached. An ice sheet, however, expands and contracts at differing rates at the top and the bottom of the ice. This internal stress causes cracks. The cracks fill with water which freezes and expands the ice a bit further. The ice sheet will expand again during the next warming spell. So what happens? The ice tends to "ratchet out" during freezing and warming cycles. This process is sometimes called "ice jacking." Under certain conditions, the ice can act like a giant bulldozer that nothing can stop, pushing lawns, soil, docks and whatever else is in front of it into piles (some over 15 feet tall!) right up against a lake home. Under particular shore and bottom conditions the ice may buckle and pile up in huge ridges in the shallow waters just off shore. Winnebago and Shawano Lakes are well-known for their huge ice shoves.

The level of ice shoving can vary greatly from year to year. Certain conditions, such as ice at least five inches thick, little or no snow cover and temperature fluctuations, may increase the likelihood of more aggressive ice shoves.

Can I live with an ice ridge?

If you are considering the purchase of waterfront property, check to see if there are signs of ice shoves (scarred trees, mounds of soil, boulders shoved up, the front of the house is missing, etc.). Just because a property is prone to ice shoves should not stop you from purchasing it. Over years, the earth ridges can strengthen and actually resist further ice shoves. Ice ridges are natural berms that can slow nutrient loading to the lakes and provide habitat. You have a number of options in dealing with ice shoves. You could let nature take its course, or you may decide to enjoy a game of "tug of war" with your lake -- you push the soil back to the lake edge in the spring and the lake returns it to your house in the winter.

In some cases, shoreland property owners may try engineering a solution. Fixes can be very expensive and may or may not have the desired results. In the past, some owners placed sloping concrete walls on their shore or ribs or runners to break up ice. If you do have damage from ice shoving, take pictures of the damage and contact the Wisconsin Department of Natural Resources (WDNR) to provide technical assistance. Depending on what needs to be done to restore the damage, a WDNR permit may be needed. You may also need a permit from your county zoning office.

Ice can be fragile, forming magical shapes that will glisten in the winter sunlight; or ice can be formidable, moving everything in its path. How should we deal with ice?


Volunteers Reaching 26,000 Boaters

As of 2006, over 640 participants from 44 counties were trained at Clean Boats, Clean Waters workshops. This certainly reflects the tremendous effort volunteers are making to help stop the spread of aquatic invasive species. Lake residents, county board members, tribal community members, representatives from county park and forest programs, boat marina operators and realtors have all attended workshops to learn how aquatic invasive species threaten Wisconsin waters. After three years of watercraft inspection and boater education, volunteers spoke to 26,000 boaters while inspecting over 12,000 boats for hitchhiking aquatic plants and animals.

The Clean Boats, Clean Waters program, sponsored by the Department of Natural Resources, UW-Extension and Wisconsin Association of Lakes, is again offering a series of training workshops across the state. These workshops provide an opportunity to learn how and why educational awareness is so important in preventing the spread of aquatic invasive species. Attendance is free, but participants are encouraged to purchase a volunteer handbook and resource tool kit for $25.

We will be collaborating this year with the Citizen Lake Monitoring Network to offer training for watercraft inspections at the boat landing as well as whole lake monitoring for invasive species. Only four selected workshops will offer Citizen Lake Monitoring Network training to focus on monitoring for specific aquatic invasive species such as zebra mussels, rusty crayfish, and Eurasian watermilfoil. Participants in these workshops will review monitoring protocols for each species and interested participants will receive monitoring equipment. Additionally, whole lake monitoring methods will be discussed to assist participants in developing a proactive approach in early detection and rapid response efforts. Attendance is free, but participants can receive Through the Looking Glass, an excellent plant identification book, and color laminated plant scans to aid in identifying underwater plants for $25.

To register for a workshop or learn more about the program, contact Laura Felda-Marquardt at or (715) 365-2659. Visit our website at

Aquatic Invasive Species: A Handbook for Education Efforts

This new education handbook was developed jointly by UW-Extension, Wisconsin Sea Grant, and the Department of Natural Resources. It includes a compilation of information on statewide programs, resources, contacts, case studies, and action strategies, along with a resource CD filled with articles, fact sheets, presentations, etc.

The handbook is available online at For further information, contact Mandy Beall (, 608/267-3531) or Kristi Minahan (, 608/266-7055).

Hold the Salt?

The Impact of De-Icing and Other Chloride-Containing Compounds on Lakes

The relationship between a lake and its watershed is clearly demonstrated by the rising chloride concentrations in many lakes. Chloride is a major component of highway deicing salts. Interest in the potential impacts of chloride on lakes was heightened when the Canadian Environmental Agency proposed designating road salts as "toxic" owing to their potential for serious environmental damage. That proposal was challenged by a variety of organizations and ultimately Environment Canada published a code of practice to help better manage the use of road salt.

Chloride is a very water-soluble form of the element chlorine. While it is found in road salt, it is also found in softening salts and some agricultural fertilizers. When chloride-containing salts are applied to land or discharged to septic systems, they eventually move into storm drainage ways or percolate into the groundwater. Because chloride does not react strongly with natural solids, it moves with the water, traveling as a dissolved ion surrounded by water molecules.

In Wisconsin, chloride concentrations are good indicators of where the water in lakes and streams originated from because natural levels of chloride tend to be quite low. For example, in northern Wisconsin, natural chloride concentrations can be less than 5 milligrams per liter (mg/l). In highway runoff and household wastewater, chloride concentrations can exceed 100 mg/l. The highest concentrations are usually found near former uncovered salt storage facilities where rain could carry salt into the ground. Groundwater chloride concentrations near these can be more than 10,000 mg/l.

How these chloride sources alter lake concentrations depends on the application rate of chloride in the watershed, the quantity of water entering the lake, the size of the lake, and the time it takes for water to travel to the lake from different parts of the watershed. Lakes in urban areas quickly receive chloride from road deicing and that has been linked to an increase in chloride concentrations in Lake Mendota from 3 mg/l in the early 1900s to 23 mg/l by 1987. Chloride use in road deicing and agricultural fertilizers increased dramatically between 1960 and 1980, and many lakes experienced chloride increases during that time. The ultimate chloride concentration in these lakes can be difficult to estimate because it may take decades for groundwater from some portions of a watershed to reach a lake, and chloride use varies throughout the watershed. Research in several groundwater-dominated lakes in Portage County shows that current lake chloride concentrations may be less than half of likely future concentrations.

High concentrations of chloride may have detrimental effects on plants and animals. It has long been known that some plants are susceptible to roadway salt applications. Research has also shown that fish and invertebrates can be harmed by short-term exposure to very high chloride concentrations. It is more difficult to characterize the impacts of long-term exposure to lower concentrations of chloride. The drinking water standard for chloride, 250 mg/l, is based only on taste, not health effects. In 1988, the U.S. Environmental Protection Agency suggested 230 mg/l as an upper concentration for protection of aquatic life. Fortunately, these concentrations are higher than the concentrations in most lakes, but recent research also suggests there may be subtle impacts on plants and animals from lower concentrations of chloride. The changing concentration may allow other species to be successful in a particular environment. For example, sphagnum moss and tamarack exhibit sensitivity to chloride concentrations, while more salt-tolerant plants such as cattails are less impacted. Researchers have found some invertebrates and algae have preferred chloride concentrations, and increases in chloride concentration could influence the mixture of species that occurs.

Another impact of increasing chloride concentrations is the influence it can have on water density. Water with a higher chloride concentration will be "heavier" than water with lower concentrations. The introduction of cooler, saltier water into lakes can change the way the water mixes. The spring overturn that characterizes most of our lakes can be reduced if deeper, cooler waters have a higher salt content. If the lake is less likely to mix, it may lead to oxygen depletion problems in deeper water.

So what can we do to help control chloride concentrations in our lakes and streams? First, remember that road salt is not the only source of chloride. Those of us who soften water can consider efforts to reduce the amount of salt we use in our water softeners. One water softener with a septic system can add hundreds of pounds of chloride to the groundwater every year. If you regenerate your water softener more frequently than necessary, you will add more chloride to the groundwater – and spend more money on salt. And if there are opportunities to safely lower chloride roadway deicing, our lakes may benefit. Remember that chloride applied to roads anywhere in the watershed will ultimately enter the lake—not just the chloride applied to roads near the lake.

As we learn more about the effects of chloride concentrations on our environment, it seems increasingly sensible to consider "holding the salt."

By Paul McGinley
UW-Extension Water Quality Specialist
UW-Stevens Point

New WDNR Lake Coordinator in Spooner

Pamela Toshner is the new Lake Coordinator at Spooner. This position covers nine counties in the west half of the northern region (Ashland, Barron, Bayfield, Burnett, Douglas, Polk, Rusk, Sawyer and Washburn). Pamela will be working with lake and river groups on protection efforts, including volunteer monitoring and lake and river grant projects.

Pamela has worked on many projects with the WDNR in Water Resources, as well as with UW-Extension as a Volunteer Monitoring Coordinator. Before working for the WDNR, she held positions at the UW Center for Limnology, Marine Biochemists, and Milwaukee Metropolitan Sewerage District. She brings excellent technical skills and experience to her new job, and we welcome her to the lakes partnership.

You can reach Pamela at 715/635-4073 or


February 18 - Southeast Regional Lakes Workshop - Wisconsin Association of Lakes Southeast Region Lakes workshop will be held at the Richard T. Anderson Education Center - Waukesha County Technical College (Pewaukee campus). For more info:

March 2-3, 2006 - American Water Resources Association (AWRA) 2006 Meeting - "Wisconsin Water Resources: Conflicts & Collaborations" in Elkhart Lake. For more info:

March 20, 2006 - Early bird deadline for the 2006 Wisconsin Lakes Convention. See pages 6-14 for details and registration information.

April 25-28, 2006 - Planning A Survey of the Nation’s Lakes - 19th Annual Conference on Enhancing the States’ Lake Management Programs - Chicago, IL. For more information contact Bob Kirschner

April 20-22- 28th Annual Wisconsin Lakes Convention - Hands Across the Waters - KI Convention Center, Green Bay.

April 28-30, 2006 - Lake Home & Cabin Show - for details call 888-471-1192 or go to

May 1, 2006 - Grants Deadlines
Lake Protection and Lake Classification Grants
River Protection Planning Grants
River Protection Management Grants


Never doubt that a small
group of thoughtful,
committed citizens can
change the world. Indeed,
it is the only thing that
ever has.
-Margaret Mead

Lake Tides -- 905032

College of Natural Resources
University of Wisconsin
800 Reserve Street
Stevens Point, WI 54481
Volume 31 No. 1
Winter 2006
Wisconsin Lakes Partnership

Published Quarterly
Phone: 715-346-2116
Editors: Mary Pardee, Robert Korth, Tiffany Lyden
Design Editor: Amy Kowalski
Contributing Editor: Carroll Schaal, DNR
Photos by: Robert Korth (unless otherwise noted)
Illustrations by: Carol Watkins, Chris Whalen
The contents of Lake Tides do not necessarily reflect the views and policies of UW-Extension, UWSP-CNR, the Wisconsin DNR or the Wisconsin Association of Lakes. Mention of trade names, commercial products, private businesses or publicly financed programs does not constitute endorsement. Lake Tides welcomes articles, letters or other news items for publication. Articles in Lake Tides may be reprinted or reproduced for further distribution with acknowledgment to the Wisconsin Lakes Partnership. If you need this material in an alternative format, please contact our office. No state tax revenue supported the printing of this document.

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