Lake & River Ice

For many of us, trekking on hard water, and staying to the openness and wind-packed snow of the landscape is what it’s all about.   The northern bush is thick and impossible to haul sleds through without cut trails and old roads.   The interconnected lake systems, often summer canoe routes, are what we seek out.  Others will travel mostly on land, along trail or old road systems.  The lucky folks in the mountains have the luxury of traveling at high altitudes where the trees thin out enough to allow travel through the forest at will.  But inevitably there will be a lake or river to cross.  It’s also great to be able to cut a water hole in the ice, dip into a slush pocket or from an open river, for liquid drinking water instead of having to melt snow.   Many people swear liquid water tastes better than melted snow, and there is a lot to that, considering the minerals and oxygen dissolved in the lake/river water will indeed impart a taste, whereas snow is mostly pure water, dust and other atmospheric particles without much dissolved oxygen.

A lone winter trekker ski hauling a sled on a lake in a snow storm. It’s low light and contrast, and he’s heading for a point and island with narrows and possibly a current. The lake is strewn with spider holes and slush pockets in this early season photo. Several potential hazards. All in a day’s trekking. Skills, knowledge and experience are used for reading ice and traveling safely.

Lakes:   Common sense combined with knowledge of ice:  That’s what you need.   Yes it’s a catch 22 if you have never traveled on ice, not gained the experience and have no mentor:  how do you gain that knowledge and experience without actually getting on the ice?

A mentor is obviously the best way to learn.  Without a mentor, you will need to ask around.  By asking around, you will find some safer lakes, perhaps ones used by snowmobilers and ice fishermen who get to know the ice well in their area.  You can also do Internet and Public Library searches on key words like “working on ice” and “safety on ice”, and you will find many resources.

There are professional courses on ice safety, including occupational health and safety courses on working on ice.   Ask your local occupational health and safety government office to investigate options for courses.  Working on ice courses  stress, among other things, to have an ice auger or ice chisel to cut frequent holes in order to assess lake ice quality and thickness.

Lake ice layers are not all equal in strength.  Blue ice or clear ice is the densest and strongest.   It forms from liquid water without snow, slush or fragments.  White ice is white because it has many air bubbles and pockets in it, and it’s less dense and weaker than blue/clear ice.   White ice forms from flooded snow and slush refreezing.

There seems to be general agreement that lake ice that is 4 inches (10.2 cm) uniformly thick and formed of blue/clear ice is the minimum that is safe for people walking, skiing, snowshoeing.   The problem is that most lakes do not have uniformly thick ice.  Currents will erode ice and bring warmer water to the surface, thinning it.  Groundwater discharge or springs are warm water in winter (perhaps 6-10 degrees C), and can also melt lake ice.   So you must always be on your guard.   There is no standard for white ice thickness safety since it’s so variable.

All lakes with a surface outflow will have currents in the lake caused by the through-flow of water.  Even isolated lakes without a surface creek outflow will likely have some kind of a current since they are fed by groundwater and discharge through groundwater.  Be on your guard for where stronger currents might exist.  Common locations are narrows in lakes.  Even though you think there may not be a current in a particular lake location, there may in fact be a strong one, thinning the ice.   Islands will interrupt the current and cause an increase in flow speed around them, and may be a place of thin ice.  Points jutting out into the lake cause currents to move quickly around them, thinning ice at the tip of the point.   Generally, I and my buddies give points a wide berth instead of crossing them too close to the land.   Inevitably one has to travel some narrows and between islands and its always a place of heightened awareness.  We hug the shallower shore or just don’t enter.  There is no one piece of advice that covers all situations.  You may have to creep along the shore or cut up into the bush.  Use your ice auger or ice chisel and make some holes, testing the ice.

Open water and hazardous thin ice at a narrows in a lake, and the point entering the lake is an esker likely with groundwater discharge. Photo on left taken on Dec. 30, 2006, and photo on right taken Dec. 31, 2007, both in low light overcast conditions. In 2007, the ice is covered with enough snow to mask the hazard. Very scary. The only way through is to detour over land across the point in the foreground off the photo, which is an island and has the groundwater link severed. You must use landform cues to anticipate hidden hazards, i.e. don’t go through narrows in the middle or across the ice tip of points.

Deep glacial deposits, especially coarse sands, stony and cobble strewn glacial tills, and eskers will often carry ground water through flows.  This water is relatively warm water in winter, and it can discharge to the surface of a lake as springs or a diffuse seepage, melting the ice and disguising it as thin ice with a skiff of snow on it.   Look at the landforms and learn about soils and groundwater.

Large boulders just below the surface, or above the surface will absorb sunlight and heat up, sometimes melting the ice around them.

Big lakes have another ice dynamic caused by wind that small lakes don’t have:    pressure cracks.   Pressure cracks are caused by the wind literally moving the ice and pulling it apart, crushing it together or moving ice plates sideways past each other.  If you know about geological plate tectonics, it looks much the same the same on the ice:  plates pull apart creating wide open leads;  plates crush together pushing up into jagged ridges sometimes well over a meter high;  and plates slide laterally by each other sometimes with open leads and sometimes with pressure ridges.  Every year snowmobilers die, (usually at night when they should not be riding), by falling through open leads of pressure cracks, or hitting a ridge at high speeds, even when the lake ice may be very thick and seemingly very safe and stable.   Strong winds can create pressure ridges and open leads in minutes, even on ice a meter thick.  The power of the wind and moving ice is truly incredible.

As self propelled winter trekkers you are traveling slowly in the daylight and have the time to observe these phenomenon and pick your route.  Pressure ridges are often very thick in refrozen slabs of thick ice, so often you can cross safely, but watch out for laterally moving ridges which may have both ridges and open leads.   You may have to travel along a pressure ridge-lead for a long distance to find a safe place to cross.

Obviously you don’t travel at night on unfamiliar ice.   In addition to the hazards already mentioned, there are overflow and slush hazards (see below).  If you know your lake ice and are confident about it, then a nighttime snowshoe and ski to see the stars and howl at the wolves can be perfectly safe.  Just don’t be traveling long distances at night.   As it gets quite cold at night and the ice starts booming as it cracks, water can spurt up through cracks very quickly, so in those booming night conditions, its far better to be on shore listening, snug around the fire or stove, or sleeping.

River Ice:   In my area of northern Ontario, there are very few rivers with ice safe enough to travel on, so we generally stay off them.  Very slow meandering creeks are sometimes useable, but beware any narrows where the water flow will speed up.  Larger rivers can sometimes be traveled or crossed in certain sections with extreme caution.   Use your auger or ice chisel to cut test holes.

Large rivers in flat gradient sections, in places with consistent deep cold winters can sometimes be traveled along.  Often only the shoreline ice shelf is safe enough.  River water goes up and down, and there can be dangerous ice caves underneath river ice, where, if you fall through, you can’t get back up through.

Open stream flowing from a lake through a culvert under a bush road. Travel on this stream even if you could find ice, is impossible. If you had to cross it, it may take a while to find a safe crossing, or you may have to make a bridge out of poles cut from the bush.

I generally don’t travel rivers, and on this website we strive to impart knowledge based on experience.   I have read many accounts of successful river travel on large rivers with thick ice in the far north of Canada, where the ice is very thick and there are open dry land shorelines to travel on as well.  Large rivers often have non-forested shorelines due to flooding and ice scour during spring break up.    On smaller rivers there often is no shoreline to travel on because the trees and shrubs are thick right to the shore.

Outflow of lake, flowing through a road culvert towards the foreground. Give the area a wide berth since the current and thin ice will extend well back from the visibly open water. Note the otter slide track in the foreground.

When trekking on canoe routes in winter, you must be aware that the portage landing locations around rapids are sometimes well within the advanced current zones.  So portage trail landing areas may be hazardous ice.  So be very careful if planning a winter trek on canoe routes where the portages are along moving water sections.

If you do travel rivers safely, we look forward to hearing about your travels on our Discussion Forums.

Ice picks and Safety gear:  When traveling on ice, you should always be wearing a pair of ice picks that are instantly accessible, i.e. they must be on a safe lanyard around you neck, or clipped to your front upper body so that should you fall through the ice, they won’t get tangled up, and you can get to them instantly.  The picks are used one in each hand to pull you out.

Unless the ice is completely known through experience to be very safe where you are traveling, you should be wearing a daypack with survival gear in it.  Sometimes I break this rule of the daypack and strap it on my sled in order to stay drier, but it’s a managed risk.  If you fall through the ice and loose your sled, your day pack worn on you with its gear may help save your life.   Simple things like having a waterproofed set of replacement socks in your daypack can make all the difference to a survival situation.  Obviously you need waterproofed matches with a waterproof striking surface, and waterproofed lighters for starting a fire, with several backup sets of matches and lighters.  Butane lighters will not light if they are too cold, so they should be stored in inside warm layers.

Ice picks. The points recess into the handles and you wear the lanyards around your neck. The lanyards have to be long enough to allow for full arm swings for pulling out. On the left are a home made pair using hockey sticks and galvanized ardox nails, cut off and filed sharp, with a strong climbing cord lanyard. On the right are store-bought Normark/Rapala Ice Claws.

Once out of the water, do not stand up!  If you do, you might fall back through the ice.  Roll away or slither with arms and legs spread out to distribute your weight until you reach thicker ice.   Then before you stand up, roll in the snow, which will assist in squeezing out and absorbing some of the water in your clothing.  When you stand up, all the water will flow down through layers of clothing, soaking anything which was not completely soaked.

OK, now you have pulled yourself out of the water and are back on safe ice.  Now what?  If traveling in the forest, you have the option of lighting a fire inside the bush, out of the wind.  If a fire is not an option and you have your sled, you have your sleeping bag, bivy bag and tarps, and can strip off your wet clothing and crawl in to shiver and recover.  Your buddies can help in several obvious ways, including getting into the sleeping bag for skin to skin contact re-warming.   Please refer to our Sleeping Systems section under the Equipment Main Section for more on sleeping systems that are robust enough to deal with this type of situation.

Hauling sled (using classic arm wrap technique on the across-the-chest harness), on slush prone early season ice. White ice picks are hanging on the front of the trekker’s blue top. The daypack with survival gear is on the sled, so this is riskier than wearing your daypack while hauling on ice.

If it’s very cold, your hands will soon lose dexterity.  If by yourself, working lighters can be impossible with hands that are freezing.   Matches may be better, but you must have a dry striking surface handy.   You need all your skills to find a wood and kindling supply, and get a big fire going.  Or get into that sleeping system, and you must also make sure your sleeping bag does not get soaked – hence the bivy bag or tarp.   Have your sleeping toque and balaclava stored in your sleeping bag drybag.   Yes, you should have your sleeping bag packed in a drybag for just this occasion of a sled that may hit the water but which can be retrieved.  If you are alone and your sled is lost through the ice or not retrievable, then you are in real bad trouble, and the fire is going to be your only hope.   Self rescue gear in your daypack will be essential.

Dr. Giesbrecht of the University of Manitoba, is an cold and winter physiology research specialist, affectionately known as “Dr. Popsicle” in popular articles.  Dr. Giesbrecht has co-produced several excellent downloadable videos and documents on real falling through ice events and how to subsequently deal with your situation.   His website link at U of M is

We highly recommend this website as a key resource to learn more about ice safety, self rescue, hypothermia and frostbite.