This winter has felt like a long one. The final weeks before opening water always do, but this year has felt extra drawn out. Numerous cities in Minnesota have broken their snowfall records and ice is still firmly on the lakes around Ely. To the Boundary Waters enthusiast, this is a painful time of year wondering if the lakes will be paddleable before an early-May or mid-May permit. And even if the ice is off the lakes, spring is a potentially hazardous time of the year with low water temperatures and strong currents that make preparation and situational awareness extra important. Just last week, Sawbill Outfitters‘ Ice Report stated “31” of total ice, with 8″ of compacted snow and 23″ of ice of varying quality.” Ely is looking a little better but, even still, canoe season for most entry points feels a ways out yet.
In the BWCA calendar, there are few hard and fast dates. One of those is May 1 when reservable permits become mandatory in time for canoe season. This appears to be yet another year though that the BWCA will not be very paddleable by opening day. This bodes the question, “how often is the BWCA actually paddleable on May 1?” The follow up questions, of course, have to do with specific permits. “If I have a permit for May 10 for Entry Point #, will I be able to take my trip?” “How strong will the currents be around that portage?” “Will the water still be SUPER cold?” For this article, I dove into the MnDNR, MPCA, and USGS data to find out. Let’s check it out!
Question number one is about ice out. Truthfully, there isn’t a ton of data to be had on historic ice out for BWCA lakes. There is ice out data though for a few entry point lakes or lakes which lead to entry points including Vermillion, Burntside, Fall, Seagull, Saganaga, Gunflint, and Clearwater. Sawbill data was omitted as it was too inconsistently recorded. From that data, the median ice out date for these lakes was found to be May 9th, a little over a week after “opening day.” That number doesn’t cover all of the entries of course as some of the creeks and rivers open a good while earlier. Looking deeper into the data then, I began to calculate out the odds of being able to take a canoe trip at different dates based off of the data. Line one is the odds of sneaking in a canoe trip in the first half of April well before opening day. For the data available, there was about a 9% chance of ice being out in any given year. The odds of having ice out in the couple weeks leading up to opening day (and being able to take that canoe trip on May 1) are about a 50% chance. If your permit is for May 8th, a week into the season, that chance goes up to 76%, 92% in the week around fishing opener, and is about 99% for June 1st (the lone dissenter being a June 3 ice out in 1936 on Gunflint Lake.) Another point to note on the data is that the lakes along the Gunflint Trail usually ice out later than the Ely side with an Ely permit being nearly twice as likely to have ice-out for opening day as the Gunflint on the data available (67% chance for Ely vs 37% chance for the Gunflint) and that trend continues heading into summer. The graph below shows the odds for each data marker for the seven lakes with data.
The second spring data set pertains to stream flow rate (cubic feet per second.) There are a number of USGS measuring stations in the Kawishiwi River, one in Basswood Lake, and a former one in Lac La Croix. Since the Lac La Croix one ceased to measure a few years ago, there’s no current data to compare to historical trends. Stream flow data is one of the variables helping to gauge flood stage. After spring rains and snowmelt, the flow rate usually increases, peaking after ice out, before gradually dropping into the summer. On dry years like 2021, flow rate drops pretty quickly. On flood years like 2022, it surges into astronomical numbers through May before dropping slowly through the summer. Starting with the Basswood data, historic averages show it having a flow rate of 1115 cubic ft/second, 2612 by opening day, 3937 two weeks later, dropping to 3415 by June, and 2722 by July. For perspective, last year, which saw incredibly high water through May, Basswood had 2972 cubic feet per second flow by opening day, but surged to 8,970 a couple weeks later. This year, 2023, we had 1630 cubic ft/second flow two weeks before opening day and are currently at 5900 cubic feet per second, meaning water is really moving fast from this year’s snow (even below the ice.) The South Kawishiwi measuring station, by contrast, tends to start its flood stage earlier than Basswood as one would expect from a river. Averages are 410 cubic feet/second two weeks before opening day, 1414 for opening day, and dropping to 1378 two weeks later (and following the trend of Basswood going into summer.) This shows how river routes tend to hit “spring” sooner than lakes with earlier ice out and earlier flooding due to their positions in the watershed and moving water. This year was 238 two weeks before opening day and is currently at 2030 cubic feet per second which is higher than usual at this time (again, due to the snow this winter.)
The final metric of spring is water temperature. Of course water freezes at 32 degrees fehrenheit and then begins its thaw heading towards summer as part of the ice out process. The only data I have for water temperature is from the Kawishiwi river, but it does give a glimpse into the process. On an average year, the water temperature has begun to warm by April 1st. Average water temp on March 1st is 33, by April 1st it’s 35, halfway through April is 37, and by opening day the water temp is averaging 43 degrees. Two weeks later, it’s 50 degrees, 62 degrees by June, and 63 by July on average. This year, the water temp was 33 on March 1 (the same as the average), then 34 on April 1st, 35 halfway through April, and was sitting at 37 on April 28, five degrees off of the May 1st average. This is another good illustrator of the distance we still have to go till true spring and summer. A chart of this data is below.
One doesn’t need the data to know that this has been quite the winter, but it lends perspective into how variable this incredible landscape of ours really is. Those of us who are itching for open-water will just have to wait a little bit longer as the ice is just starting to pull away from shore here in Ely. Hopefully some warmer days, rain, and a little wind will help open the lakes up. For those of us with first week of May permits, it’s not looking hopeful that we’ll have open water unless we’re taking a river route. Because of this, it’s important to remember to be safe on the water. Late spring means the whole process pushes back and some lakes may still be quite cold Memorial Day weekend. Now is the season for anxiously reloading the DNR ice-out map, watching and waiting for the reports to creep north. Before we know it, ice will be out and another canoe season will be just at hand.
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