Warmer weather at Okoboji: What it means for the lakes and those who use them
First of two columns: Our changing climate and how it affects Okoboji and Iowa.
The ice on Spirit Lake went out this year on March 3.
That is the earliest ice-out day in the 77 years the Iowa Department of Natural Resources has been keeping records.
From 1944, when the record-keeping began, through 1981, the ice went out in the latter half of April about once every third or fourth year. Since 2001, the ice has gone out in the latter half of April only once.
Looking at it another way, the ice cover on Spirt Lake has been decreasing in terms of how long it lasts each year for the past quarter-century or so. The longest ice cover on record was 154 days in 1955. From 1955 through 1978, the average number of ice-cover days was 135. However, from 2001 through 2020, the average dropped to 106 days, a decline of 27 percent.
The obvious conclusion is that the water temperatures in the Iowa Great Lakes are getting warmer, a result of ongoing global warming, which is part of our overall climate change.
Mary Skopec, executive director of the Iowa Lakeside Laboratory at Okoboji, pointed to these figures in a recent interview focusing on what climate change is doing to the Iowa Great Lakes.
Skopec, a Ph.D. in environmental science and formerly a senior scientist with the Iowa Department of Natural Resources, talked about a number of significant and dramatic changes in the Iowa Great Lakes stemming from the world’s changing climate. It is not a pretty story.
The headlines:
Expanding clusters of a previously uncommon algae …
…are depositing toxins in the lakes. The toxins can attack the liver. They can cause severe nausea. Some of them are neurotoxins. Wildlife and pets that like the water are at risk to these toxins. The City of Orleans has found the toxins in the drinking water it takes in from Spirit Lake – although the toxins did not make it past the intake pipe. They have not shown up in the city’s treated water supply that flows into homes and businesses. Still, it is a cautionary signal, at least. In 2022, there were postings on Spirit Lake for algae-infested areas, cautioning against swimming in these areas. Warning: If you see bright green algae, known as blue-green algae, on one of the Iowa Great Lakes, keep your dog out of the water.
Invasive species are creating thick green carpets …
…on a lake’s surface, making it virtually unnavigable. This has happened in areas of East Lake for relatively short periods of time. How bad can this get? In Minnesota, Skopec said, portions of some lakes, including Minnetonka, the state’s crown jewel among its thousands of lakes, have become unusable. Footnote:
The troublesome blue-green algae also can result in fish kills …
…in certain circumstances. It happens when the bad algae grows a lot, and then dies back, which, in turn, depletes the oxygen in the lake. In Spirit Lake, East Okoboji, Center Lake, Lower Gar, and Minnewashta this has resulted in fish kills numbering up to several hundred at a time.
Curlyleaf Pondweed thrives under the ice when snow cover is light …
…then wreaks havoc when the ice melts. It dies beginning in late June, but has become a problem in East Lake, producing thick beds of weeds at the beginning of the Lakes season. The Pondweed roots in the bottom of a shallow lake like East Okoboji and rises virtually to the surface. In one recent year, the entire lake was covered with Pondweed for a time. “You could not boat through it. . . It was tangling up in your prop,” Skopec said.
Ticks carrying bacteria related diseases that nobody wants…
…likely loom in the future of the Iowa Great Lakes. Additionally, a warm water disease, the dreaded brain-eating amoeba, used to be confined to southern areas. Now, it is moving north. Last summer, a case arose from a lake in southern Iowa, just 200 miles south of the Iowa Great Lakes.
The changes in the lakes area resulting from warmer temperatures can be found not only in the lakes themselves but in the life and land around the lakes.
Tornadoes…
…a rare but real threat around the Iowa Great Lakes, can be much larger and much more damaging today than they used to be. One study showed that tornado power has been increasing by more than 5 percent a year in recent years. Another showed that the size of a tornado increases as water temperatures increase. Skopec noted that those who monitor tornadoes are talking about creating a new F6 category because tornado wind power is beginning to go beyond the upper limits of the F5 category, which is the top category. Warmer temperatures, again, are a factor.
More frequent flash floods and more droughts …
…have begun to become a reality. There are heavier, more frequent rainfalls than what used to be the norm. The floods not only cause property damage and inconvenience, they produce damaging lake shore erosion. At the same time, the increasingly long dry spells have produced more droughts, which are lowering lake levels. In East Okoboji, this is one of the factors leading to the Curlyleaf Pondweed invasion.
Among all of these problems, the most troublesome has been what is known as the blue-green algae, even though its color looks bright green on the surface. These algae blooms are fueled both by warming water temperatures and by excessive nutrients – phosphorous and nitrogen – coming into a lake from landscaping runoff around the lake and from agricultural land draining into the lake. The bad blue-green algae tends to overtake the good algae, which produces necessary nutrients.
In addition, lakeshore erosion or a bank collapse can dump nutrients into the water. Heavy rains used to be one to one-and-a-half inches, Skopec said. Now, we see two, three, and four-inch rains. Beneficial vegetation in the lakes gets drowned out. Water levels erode the banks and harmful nutrients rush in. All of which sets up the bad algae blooms.
Overall, the least affected lake in connection with most of these water-warming issues is West Okoboji, Skopec said. It is deeper and the water at the deeper points is much colder than the water at the bottom of the shallower lakes – East Okoboji and Spirit Lake. West Lake is deeper than either of the other two by as much as 100 feet. West Lake also has more surrounding wetlands than the other lakes, thus providing some protection against adverse agricultural runoff of nutrients.
“Sometimes we see the harmful algae in shallow areas or embayments, but not very often,” Skopec said, adding that the beaches of West Lake rarely have outbreaks of the harmful algae fields.
Looking ahead, however, there are a couple of issues that could touch on West Lake.
The fragility of both Spirit and East Lake resulting from their shallow depths, warmer water, and warmer weather could make parts of them unusable at times. East Lake also is at risk because of its history. The Indians considered it more of a marshland than a lake. Its depth was artificially maneuvered for some increase during the early years of development in the Lakes Area.
With Curlyleaf Pondweed spreading across the bottom of the lake and longer droughts resulting in loss of water depth, could East return to its marshland status?
All of this at least raises the possibility that people who live on East and Spirit might be forced to move their boating activity to West Lake. Skopec recalled that when Curlyleaf Pondweed made much of East Lake problematic for boating one recent year, many boaters from East Lake did move over to West.
How many people can we put on West? Skopec asked. There are only so many square acres of water.
Additionally, the threat of drought and lower lake levels would affect West Lake as well. Among other things, East Lake and West Lake are connected. If East loses water depth, West will lose it. It still would be a deep-water lake, but if that loss of depth becomes as much as 10 or 15 feet, how much longer would dock lengths on West Lake have to be to allow private boats to dock and be raised into hoists?
Solutions to all of this?
Yes, there are a few. Increasing vegetation in the lakes and harmful algae blooms can be managed to some extent with herbicides. They already are being used on Curlyleaf Pondweed, even though it keeps coming back.
More wetlands around the lakes also would help, both in slowing agricultural runoff and the runoff during heavy rains.
Can individual Lakes area residents play a role in minimizing the climate change impact on the lakes? Skopec said they can. Here’s how:
Avoid fertilizers containing phosphorus
“None of our soils around here need phosphorus,” Skopec said. It just runs into the lake and causes those bad algae blooms, she said. Minnesota, she noted, prohibits the use of fertilizer containing phosphorus. In Iowa, however, phosphorus is regulated by the Department of Agriculture. “I don’t think they have any interest in banning phosphorus fertilizer around lakes in Iowa,” she said.
Plant deep-rooted native vegetation on the banks …
…around the lakes that will help hold the banks in place even in adverse weather situations. One example is the Purple Cone Flower, which develops six-foot-deep roots but does not grow tall, so it will not intrude on the lake view.
Consider natural landscaping …
…instead of grass and sprinkler systems – things that do not require sprinkling systems and are drought tolerant. “The added benefit is all the wildlife, the bees, the butterflies, the birds, they love it, too,” Skopec said.
The bottom line in all of this? Skopec put it this way:
“We can manage the vegetation. We can manage the harmful algae blooms. We could try to manage the nutrients.
“But we can’t change how much rain we have and how hot it is. Those things are outside our control.”
Saturday: The bigger picture. Why climate deniers are wrong, the global warming problem, and how Iowa is in a special position to help solve the problem. First of two columns: Our changing climate, and how it affects Okoboj and Iowa.
Thanks, Bob. Good possible follow-up items.
Managing the vegetation and algae with herbicides would certainly be the Iowa way. What could possibly go wrong?