Warming Lakes: Climate Change and Variability Drive Low Water Levels on the Great Lakes

Low water levels expose the sandy lake bottom on Lake Michigan. Photo by Jeff J. Cashman.


For people living around the Great Lakes, water levels this past month have appeared much lower than many will remember. The upper Great Lakes reached near-record low water levels in October. This was most evident on Lakes Michigan and Huron, where lake levels dropped to less than two inches (4 cm) above record lows and 28 inches (71 cm) below the long-term average. All five lakes, plus Lake St. Clair, remain below their long-term averages.

Rock and sand recently exposed by low water levels made stretches of the northern Lake Michigan shoreline look like a moonscape. Recreational boaters had trouble navigating the shallow water this fall, and shipping companies lightened loads to compensate for low water. Lakes Michigan and Huron hovered just above a record low set nearly 50 years ago, and Lake Superior was within five inches (11 cm) of a record low set in 1925.

A 2002 National Geographic magazine story, Down the Drain: The Incredible Shrinking Great Lakes, documents declining lake levels and the potential economic and ecological consequences for the region. Ten years later, the story continues to unfold, as water levels remain lower than normal.

Experts blame the recent low water on the unusually warm and dry weather over the past year. Rain events in October, including Hurricane Sandy, delayed the inevitable, but forecasters predict Lakes Superior, Michigan, and Huron will likely reach historic low levels in the late fall or winter, a time of year that the lakes are normally already dropping due to high rates of evaporation.

Photo: Low water on Little Sand Bay, Beaver Island, Michigan. Photo: Jeff J. Cashman.
Water levels on Lake Michigan were within two inches of record lows in October and are expected to continue dropping as part of the normal seasonal decline through fall and winter. Photo by Jeff J. Cashman.


Low water levels are not the only climate-related trend being observed on the Great Lakes. Ice cover is also declining. The Great Lakes have lost 71% of their ice cover since 1973, according to a study by the Great Lakes Environmental Research Laboratory (GLERL). This past winter, the Great Lakes, including Lake Superior, were virtually ice free with just 5% ice coverage, the second lowest on record. Similar to the global assessment conducted in 2000, loss of ice cover is being reported on lakes throughout North America, Europe, and Asia.

Photo: Miners Castle, Pictured Rocks National Seashore on Lake Superior. Credit: John Lenters.
Lake Superior is one of the most rapidly warming lakes in the world.

Summer lake temperatures are also on the rise. As mentioned in one of my previous posts about warming lakes, the Great Lakes are among many lakes in the northern hemisphere experiencing a rapid warming trend. Lake Superior, the largest freshwater lake in the world by surface area and third largest by volume (after Baikal in Siberia and Tanganyka in Africa), is also one of the most rapidly warming lakes in the world.

Because lower lake levels are considered one of the potential consequences of climate change, I was curious to find out whether there was any connection to what is being observed on the Great Lakes.

I recently had the opportunity to talk with John Lenters, a lake and climate scientist, while we attended a meeting of the Global Lake Ecological Observatory Network (GLEON) in Mulranny, Ireland. When comparing notes about our personal connections to Lake Superior, I learned that this accomplished scientist, with a laid-back, Midwestern manner, first fell in love with the Big Lake as a 14-year-old boy while on a backpacking trip in Isle Royale National Park. “Although the trip was grueling, I was awed by Lake Superior and realized I wanted to study lakes,” Lenters told me.

Now an associate professor at the University of Nebraska–Lincoln (UNL), Lenters studies lake-climate interactions in the Great Lakes region, the Alaskan Arctic, and western Nebraska. Given the global implications of his research, he joined GLEON in 2008 and helped to form the new Global Lake Temperature Collaboration (GLTC), hosting their first meeting at UNL this past June. With his boyhood dream as inspiration, he and his collaborators are leading the way to learning more about how climate change is affecting lakes around the world, including the Great Lakes.

Photo: Sunset on Granite Island, Lake Superior. Credit: John Lenters.
Sunset on Granite Island, Lake Superior. Photo by John Lenters.


On Lake Superior, Lenters and his collaborators are studying the interactions among evaporation, ice cover, and water temperature. Their research builds on work by others in the region (and elsewhere) and provides new insight on factors affecting water levels.

Surface Water Temperatures Increasing on the Great Lakes

Similar to Lenters’ findings in a 2004 paper, which found Lake Superior to be warming more rapidly than summer air temperatures, Jay Austin (a GLTC collaborator) led a study of lake temperature trends at the University of Minnesota-Duluth’s Large Lakes Observatory (LLO). Published in Geophysical Research Letters, the LLO study found that summer surface water temperatures on Lake Superior have increased approximately 4.5°F (2.5°C) during the period 1979–2006.

The LLO study found that the decline in winter ice cover leads to an earlier start of the summer stratified season, a natural process in lakes when water near the surface warms, while deeper waters remain a more constant, cooler temperature. The earlier the lake becomes stratified in summer, the longer the warming period. “This results from a progressively earlier start of the summer stratified season, in response to a significant decline in average winter ice cover,” the study states. “Given a longer summer stratified season, surface waters can be heated to higher temperatures than that expected from increases in air temperature alone.”

Researchers also found a clear relationship between ice cover and summer water temperatures, which tend to be cooler following a winter with extensive ice cover. In contrast, winters with less ice cover tend to be followed by a summer with warm surface water temperatures. This is exactly what happened this year on Lakes Superior, Michigan, and Huron. The lakes were relatively ice free in 2011–12 and reached record-high water temperatures in the summer.

New Insight About the Interaction Between Ice Cover and Evaporation

Measuring evaporation rates on lakes as large as Superior is a very difficult and intensive process, so until recently, researchers in the Great Lakes region relied on models instead. The models correctly account for the various factors that impact evaporation rates, including when the lake surface is covered by ice. But with ice cover shrinking on all of the Great Lakes, scientists began to wonder what impact this would have on observed evaporation rates. Understanding this new dynamic required the installation of new monitoring stations on all five of the Great Lakes. Results are being shared through a network of researchers monitoring evaporation rates.

Photo: Evaporation monitoring station on Granite Island, Lake Superior. Credit: John Lenters.
Lenters and his collaborators established a monitoring station on Granite Island in Lake Superior to measure evaporation rates. Photo by John Lenters.


In the past, experts assumed that as ice cover decreased, evaporation would increase, since more of the lake’s surface is exposed to the air during winter months. But a new paradigm is emerging.

“Some of our recent work challenges the standard paradigm that more ice cover means less evaporation,” Lenters told me. Evaporation rates are increasing as the climate changes, but the relationship to water temperature and ice cover is not as simple as previously thought.

Katherine Van Cleave, Lenters’ former student at UNL, recently completed a study of these interactions for her master’s thesis. Her study includes an analysis of the first direct observations of nearshore evaporation rates on the Great Lakes, using a high-tech monitoring station on Granite Island, near Marquette, Michigan. She also looked at some of the primary climatic factors driving this variability. Although her study period, from October 2010 to April 2012, does not include this past summer, the impact of the warm 2012 water temperatures on evaporation rates is entirely consistent with her findings.

Photo: High-tech evaporation monitoring station on Lake Superior. Credit: John Lenters.
Scientists use high-tech equipment to monitor evaporation from Lake Superior year-round. Photo by John Lenters.


Research by Lenters at Granite Island and a study with other collaborators at Stanard Rock (published in the Journal of Great Lakes Research) has examined seasonal and annual evaporation rates on Lake Superior. Together with research by Van Cleave, they found that evaporation rates in late winter and early spring (when ice cover is typically at a maximum) are generally minimal, even in years with low or no ice cover. The highest rates of evaporation, on the other hand, occur during the fall and early winter and, during particularly cold years, can actually lead to greater ice cover later in the winter and spring. “Evaporation is a cooling process,” explained Lenters, “and the more rapidly it occurs, the more likely the lake is to reach freezing temperatures and form extensive ice cover.”

Evaporation from a lake is similar to how we humans perspire to cool our bodies on a hot summer day. It is a process that transfers heat from the lake back into the atmosphere. When a lake evaporates, heat is released to the atmosphere. The more the lake “sweats,” the more it cools.

So instead of simply thinking of ice cover as a “cap” on evaporation, we need to realize that the reverse is also true – that strong evaporation can lead to high ice cover. In other words, says Van Cleave, “this ‘standard paradigm’ of decreasing ice cover, increasing water temperatures, and increasing evaporation may not stand as a full explanation of the role of evaporation in these processes. More evaporation in the fall will cool the lake quicker, leading to an earlier onset of ice cover.”

Photo: satellite photo of Lake Superior in February 2012. Source: NASA.
The Great Lakes, including Lake Superior, were nearly ice free during the winter of 2011-12. Source: NASA MODIS satellite photo from NOAA Great Lakes Coastwatch website.


But the lack of ice cover affects evaporation in another important way – by impacting water temperatures and evaporation rates much later in the year. “Ice cover was found to be a strong determinant of summer water temperature, and this in turn, can lead to changes in late-summer evaporation rates,” Van Cleave concluded.

Regime Shifts in the Great Lakes Ecosystem

Photo: Monitoring station on Granite Island, Lake Superior. Credit: John Lenters.
Van Cleave found a regime shift in the Great Lakes ecosystem after extreme climate conditions in 1997-98. Photo by John Lenters.

Van Cleave made an interesting discovery after looking at long-term data for Lake Superior: Certain changes have not been linear through time. Scientists use statistical analysis to see if patterns emerge in their data and to determine whether certain parameters are increasing or decreasing with time. “Lake Superior experienced a pronounced change during the winter of 1997–98 when ice cover reached, at the time, record low levels,” her report states. “This was followed by record-warm summer water temperatures and near-record evaporation rates (surpassed only by 1987).”

“A step-change occurred in 1997–98 that resulted in a drop of ice duration of nearly 40 days, a 5.4°F (3°C) increase in summer water temperature, and a near doubling of July-August evaporation rates,” Van Cleave concluded. Ecologists refer to an abrupt change such as this as a regime shift, and although some evidence indicates that the lake recovered somewhat, Van Cleave found that these more recent trends ”are not statistically significant, suggesting that the 1998 regime shift has largely been sustained.”

Given the extreme conditions of this past year, Lenters wonders whether Lakes Superior, Michigan, and Huron are in the midst of another such regime shift.

Lake Levels Remain Below the Long-term Average

The U.S. Army Corps of Engineers (Corps) began keeping coordinated water level records in 1918. They base “record events” on calculations of monthly average lake level. Lake Michigan-Huron, considered one lake for hydrological studies because of the connection at the Straits of Mackinac, was 576.6 feet (175.74 meters) above sea level in October. The all-time record low for all months occurred in March 1964, when the lake dropped to 576.0 feet (175.58 meters).

The Great Lakes Water Level Dashboard, a handy, interactive online tool provided by NOAA, helped me to better visualize historic water level trends going back to 1861. I was reminded of a period of high water on the upper lakes during the 1970s and 1980s, when everyone was concerned about erosion along the lakeshore and houses were falling into Lake Michigan. What also jumped out are the below-average water levels after the 1997–98 event that Van Cleave described.

Photo: Great Lakes Water Levels, 1918-2012. Source: NOAA Great Lakes Water Level Dashboard.
Screenshot of NOAA’s Great Lakes Water Level Dashboard showing Lakes Superior (top) and Michigan-Huron for the period 1918-2012.


Great Lakes water levels normally fluctuate throughout the year and from one year to the next depending on climate conditions. The lakes naturally cycle between periods of high water and low water, but abrupt changes in annual water levels are not unusual. These fluctuations are due to climate variability and are considered vital to a healthy ecosystem.

One variable the Corps constantly monitors is the supply of water to each Great Lake, which is made up of rainfall on the lake surface, runoff to the lake, and evaporation from the lake. In a teleconference with the media, Keith Kompoltowicz, chief of the Watershed Hydrology Branch in the Corps’s Detroit District Office, explained that this supply is the primary driver of water level fluctuations and that this past year, evaporation was much greater than precipitation and runoff combined. “Any time there is a scenario like that, lake levels will likely decline,” he said.

Lake levels are expected to continue dropping as part of the normal seasonal decline through the fall and winter. “Evaporation usually wins out at this time of year,” said Kompoltowicz.

Photo: Low water in St. James Harbor, Michigan. Credit: Jeff J. Cashman.
Near-record low water levels on Lakes Michigan and Huron in October hovered just above a record low set nearly 50 years ago. Photo by Jeff J. Cashman.


Lakes Superior, Michigan, and Huron have been fluctuating below average levels since the extreme event 15 years ago. Corps officials acknowledged that the upper lakes have not recovered from this extreme event and are not likely to anytime soon. “We would need several months and seasons in a row of very wet weather to get us back to long-term average,” said Kompoltowicz.

This extended period of low water raises questions about whether climate change is contributing to declining lake levels, but the Corps maintains the position that it’s difficult to know, because the lakes continue to fluctuate within their normal range.

Low Lake Levels Renew Debate About Potential Causes

Controversy usually arises about potential causes whenever lake levels are low. Numerous theories abound. People ask whether a diversion in Chicago to the Mississippi River watershed might be to blame. Others point to erosion or dredging in the St. Clair River. John Allis, Chief of the Corps’s Great Lakes Hydrology and Hydrography Office, dismissed these claims, citing studies that show the Chicago diversion is more than offset by a diversion into Lake Superior from Canada.

Allis referred to a study of historic dredging and sand removal operations on the St. Clair River. “Studies show that the net impact of historic dredging and erosion is about 10 to 15 inches lower water levels in Lakes Michigan and Huron,” he said. “The last dredging project was completed in the 1960s, and since 1967, the only dredging that has been done on the St. Clair River is maintenance dredging to keep the rivers at authorized depths.”


Photo: View of Detroit-Windsor from Lake St. Clair. Credit: L. Borre.
The St. Clair River flows from Lake Huron to Lake St. Clair and the Detroit River. Historic dredging and sand removal projects resulted in water levels that are 10 to 15 inches lower on Lakes Michigan and Huron. Photo by Lisa Borre.


The Corps says that when water levels are low, they get asked about whether structures could be built to restrict flow in the St. Clair River. “Recent studies show that any of those projects could range from $50–200 million to construct,” said Allis. “Although water is low right now, there are many groups that would not support the construction of structures because of concerns about what would happen in high water.” He explained that projects to mitigate historic water losses were de-authorized in the late 1970s when the lakes approached record high levels.

The International Joint Commission (IJC) studied the impacts of dredging and erosion in the St. Clair River on water levels in the upper Great Lakes. Among other things, the International Upper Great Lakes Study (IUGLS) evaluated remedial measures for historic dredging projects and erosion. “The Study Board found that there had been some erosion in the St. Clair River between 1962 and 2000, but the riverbed had stabilized since then, making it unclear whether action would be appropriate,” said IJC Public Information Officer John Nevin. Further details can be found in the summary report.

Photo: Ship entering the Soo Locks on the St. Mary's River. Credit: Lisa Borre.
Ships on the Great Lakes have lightened loads this fall due to low water levels. Photo by Lisa Borre.


The five-year, $14.6 million study by the Study Board also examined options for regulating water levels and flows in the upper Great Lakes system, consistent with the Boundary Waters Treaty of 1909. In March, the Study Board released its final report and recommended a new regulation plan for Lake Superior outflows, one that is “more robust than the existing plan and provides benefits, especially to the environment,” said Nevin. The new plan will not change regulation in a way that helps the situation on Lakes Michigan and Huron. “If we were to try to do that, it would damage Lake Superior,” he said. “It really can’t be done.”

Photo: The Soo Locks on the St. Mary's River, Lake Superior. Credit: Lisa Borre.
A new regulation plan for Lake Superior will make it easier for ships transiting the Soo Locks and improve spawning habitat for endangered lake sturgeon in low water conditions. Photo by Lisa Borre.


The focus on past diversions and dredging operations is not surprising, given the complex nature of more subtle but very real changes underway. I asked Lenters for his opinion on other theories that explain why the lakes are so low this year. “No one bottled it up and took it away or diverted it to the Mississippi,” he said. “Together with the low precipitation we’ve seen this year, the lake water simply evaporated more quickly.”

Management Agencies Study Effects of Climate Change

With nearly 20% of the world’s surface freshwater at play and millions invested in restoration efforts, the stakes are incredibly high for understanding how natural climate variability and human-induced climate change affect the Great Lakes.

The IUGLS evaluated the impacts of climate change on lake levels in the Great Lakes region with state-of-the-art climate research. Projections suggest that “lake levels are likely to continue to fluctuate, but still remain within a relatively narrow historical range – while lower levels are likely, the possibility of higher levels cannot be dismissed.” Nevin explained it another way. “Low lake levels are not a new normal,” he said. “We expect to see lake levels fluctuate as we have in the past.”

Photo: The North Channel, Lake Huron. Credit: Lisa Borre.
State-of-the-art climate research conducted as part of the International Upper Great Lakes Study indicates that increased evaporation due to climate change will be largely offset by increases in local precipitation in the Lake Michigan-Huron basin. Photo by Lisa Borre.


The IUGLS acknowledges that despite uncertainties in the models used, “it is clear that evaporation is increasing and likely will increase for the foreseeable future.” The study further states, “Analysis indicates that in the Lake Michigan-Huron basin this increased evaporation is being largely offset by increases in local precipitation.” The outlook for Lake Superior is more cautious:

“In the Lake Superior basin, however, increasing evaporation over the past 60 years has not been compensated for by increased precipitation. As a result, the water supply has been declining in general in the basin. This trend is consistent with the current understanding of climate change. Unless changes in the precipitation regime occur, which is possible, [net basin supply] in Lake Superior will continue to decline, on average, despite the possibility of higher supplies at times.”

Photo: Kayaking at Copper Harbor lighthouse. Credit: John Lenters.
Experts predict that Lake Superior water levels will continue to decline, on average, due to increased evaporation rates caused by climate change. Photo by John Lenters.


These findings convinced the Study Board to recommend that “further climate analysis be undertaken to explore these dynamics” in order to provide more certainty in water supply estimates. Will changes in precipitation offset increased evaporation rates? Can lake levels recover from extreme events or are we seeing a new normal? These are some of the questions yet to be answered.

The IUGLS acknowledges that the Great Lakes basin is a complex system whose dynamics are only partially understood. In addition to further research, the Study Board recommends a more adaptive approach to future management – one that places climate change considerations in the mix. As the experience on Lake Tahoe shows, an important first step was acknowledging that climate change is a major driver in the ecosystem. Lake managers there are now focused on restoration projects that build the lake’s resilience to changes that are already underway.

Photo: View of Lake Superior near Copper Harbor looking toward Isle Royale. Credit: John Lenters.
Changes in ice cover, water temperature and evaporation indicate major shifts are underway on Lake Superior, the world’s largest lake. Photo by John Lenters.


Lenters explained that this past year was like a “perfect storm” of conditions leading to high rates of evaporation and low water levels on Lake Superior. “Record low ice cover in 2011–12, an extreme heat wave in March, and a warm, dry summer led to record-high summer lake temperatures,” he said. “As a result, we saw higher-than-normal evaporation rates earlier in the season.”

Lake Superior evaporation – which is typically very low during spring and early summer – doesn’t normally begin increasing until early August. But this year it began as early as late June. Together with the summer’s below-normal rainfall, lake levels began their annual decline in the summer rather than in the fall. This would explain the near-record low lake levels in October. “Lake Superior’s rapid warming is like a canary in the coal mine,” Lenters told me. “We’re seeing changes in ice cover, water temperature, and evaporation that indicate major shifts are underway on the world’s largest lake.”


Lisa Borre is a lake conservationist, freelance writer and sailor based in Annapolis, MD. With her husband, she co-founded LakeNet, a world lakes network that was active from 1998 to 2008, and co-wrote a sailing guide called “The Black Sea.” She is a native of the Great Lakes region and served as coordinator of the Lake Champlain Basin Program from 1990 to 1997.

Lisa Borre is a lake conservationist, writer and avid sailor. A native of the Great Lakes region, she served as coordinator of the Lake Champlain Basin Program in the 1990s and co-founded LakeNet, a world lakes network that was active from 1998-2008. She is now a Senior Research Specialist at the Cary Institute of Ecosystem Studies and an active member of the Global Lake Ecological Observatory Network (GLEON). She is also on the board of directors of the North American Lake Management Society (NALMS), the advisory council of the Lake Champlain Committee, and an associate investigator with the SAFER Project: Sensing the Americas' Freshwater Ecosystem Risk from Climate Change. She writes about global lake topics for National Geographic's Water Currents blog and speaks to local, regional and international groups about the impacts of climate change on lakes. With her husband, she wrote a sailing guide to the Black Sea based on their voyage there in 2010.
  • Suzanne

    A timely and well written article about this very important issue affecting our beloved Great Lakes.

  • Jim Olson

    Thank you for slicing through the fog over Great Lakes water levels and global warming. These lakes reflect back systemic threats, like continued below level drops in water levels, nutrient loading. and invasive species that disrupt values proetced by long standing public trust principles. Great Lakes are held in public trust, which means they cannot be sold, surobordinated or materially harmed by government others. If we follow these principles, we as a country and world will get back on course to live, work, and grow within these fundamental limits. Climate chnage and global warming must be addressed now, at all levels. Some affects will require adaptation. One of these is to revisit all diversions and changes in past, inclucing Chicago Diversion – it is no longer ncessary with right principle, right technology, and conservation of water — all available. FLOW Public Trust Policy Center has filed with the International Joint Commission a paper on water levels and equitable principles applying public trust doctrine. info@flowforwater.org

    • Thanks for your comment, Jim, especially on this foggy morning around Lake Michigan. You’re right that the lakes reflect what is happening in the ecosystem, which is why they are considered important indicators of threats. The ones you identify (and others) interact in ways that require us to think more broadly about these threats, which will be a topic of a future post. The effects of climate change will require an adaptive approach, as you describe, and the IJC has endorsed for evaluating the regulation of water levels on the Upper Great Lakes.

  • Penny Pepperell

    Great article, and right in step with the view of Georgian Bay Forever that climate change is playing a big part in low water levels. Very interesting stuff about evaporation. Please include me in any email blasts you will be sending out.

  • Peter

    What a croc of crap, the most unscientific report I ever heard.”Global warming causes low lake levels” ya and Santa is warming the north pole. It must not have anything to do with man made things, like a massive new water pipe line going into the southern states, even new water bottling plants on a massive scale. Dredging the saint Lawrence for larger ships, causing a massive upswing in water flow.Record low rain falls, and a climate that goes through cycles some of them thousands if mot millions of years old, (log before man) and its impossible to know what cycle we are in. If you think your new carbon tax will fix this, you are as nutty as the guy who wrote this article.

  • jon bonadeo

    Great insight into what we always thought. Hope there is some action to slow this down.

  • Allen

    A very well written article. Many people are looking at things as normal for the lakes based on personal experience or short term records. In the late 1800’s the Great Lakes began a process of ending the little ice age. This process may still be in operation. Averages based on the last 100 or so years may not have anything to do with normal. According to a production either on Nat Geo or the History Channel, I believe it was Nat Geo, Studies by scientists at Michigan State University show that as recently as 5,000 years ago the Great Lakes were nearly dry and that a person could walk across Lake Huron. On another program scientists stated that since the advent of GPS technology it has been discovered that glacial rebound is happening at a far faster rate than previously thought with some areas rising as much as one inch a year. I remember the low water levels of 1964 and the high water levels of the 70’s and 80’s. Having spent most of the last 50 years within a few hundred feet of Little Traverse Bay, I have seen years with water over the docks in the harbor and years with 300 ft of lake bottom exposed near the harbor. If glacial rebound has been taking place at one inch per year, then the lake bottom would have risen nearly 50 inches since that time. Are people who study the lakes from a climate view also looking at the geologic information? It has been proposed that if rebound continues at the current rate or the rate increases due to less water load, then the Great Lakes may some day be nearly dry again. Scientists who study lake levels from a surface level altitude as given in this article should adjust their studies to include the water column altitude from the lake bottom as read by GPS references. If the lake bottom is raising then the water column would be shorter for the same surface water altitude. In shallow areas, the raising bottom might result in exposed bottom lands and the look of lower water levels from climatilogical influences which may, in fact partly result from geological activity.

    • You might be interested in this study by the USGS, which looked at lake level variability and historic lake levels going back almost 5,000 years using reconstructed historical data records: http://pubs.usgs.gov/circ/2007/1311/pdf/circ1311_web.pdf. They also address the issue of rebound and how this affects lake levels. The bottom line is that it affects each lake differently and has not be consistent through time.

  • Bob

    No mention is made about the companies that are pumping millions of gallons of water, “legally”, every day, out of springs in northern Michigan. These springs are connected to the lakes and yes the water is being “bottled up and taken away”.
    Climate is a factor, but not the only one.

    • This post focuses on climate because it is the major factor affecting the net basin supply of water. Climate affects both the water inputs (precipitation and runoff) and water loss through evaporation. These are the main factors controlling fluctuations in water levels.

      Evaporation is the main source of water loss when calculating net basin supply, and therefore also important when looking at what could be causing the fluctuations in water levels on the Great Lakes. I asked John Lenters from UNL to give me some numbers to help put the issue in perspective. He said, “On average, Lake Superior loses 29 billion gallons of water PER DAY through evaporation.” His calculation is based on the annual average rate, and he also noted, “The daily evaporation rate can be ten times higher during the late fall.” This is why the lakes experience a seasonal decline at this time of year.

      While the daily total evaporation numbers are impressive, the more relevant information for this discussion is what factors cause the changes being measured in the lakes on longer timescales. According to Lenters, “If the annual evaporation rate increased by just 1%, that would lead to an increased water loss from Lake Superior of 290 million gallons per day, or about 110 billion gallons per year.” This is significant because climate change is expected to lead to higher evaporation rates from the lakes.

      “Whether you compare average “human-induced pumping rates” to the average evaporation rate or “increases” in pumping rates to increases in evaporation, there’s really no comparison,” said Lenters. “We’re talking about a difference that is roughly a factor of 1000 or more.”

      This is not to say that water withdrawals and diversions are not important for other reasons. Every drop of water in the Great Lakes region is precious. Water withdrawals and diversions are carefully regulated, and local and regional impacts are considered in the permitting process. While perhaps not perfect, the process results in “legal” water withdrawals as you describe. It’s just that these water withdrawal rates do not even come close when it comes to considering water losses due to evaporation and their overall effects on water levels in the Great Lakes region. The lakes are warming and evaporation is increasing due to changes in climate.

  • Al Taylor

    The dredging of the St Claire River is the culprit, in my opinion
    A speed bump of sorts would slow the outflow and allow Lakes Michigan & Huron to rise. Blaming climate change AKA weather is a distraction & the “do nothing report” from the IJC is not an option. Its all about $$ & government. Get on with stemming the flow in the St Clair.

    • Although experts believe that the St. Clair River is not actively contributing to the problem of low water levels, their research documents that historic dredging operations and water diversions did result in lowering the level of Lakes Michigan and Huron by 10-15 inches. If climate change and variability cause low water levels to become the “new normal” on the Great Lakes, government agencies may need to revisit decisions about measures to mitigate historic losses, such as “speed bumps” to slow the flow of water in the St. Clair River. When determining the feasibility of mitigation schemes, agencies (and interested citizens) should also take into account the very real changes underway due to a warming climate in the region. Climate change considerations are not a distraction, but they do add a layer of complexity to the decisions.

      In addition to the reasons cited in the above post, the current “do nothing” decision on the St. Clair River is based in part on an IJC feasibility study about the effects of climate change. Their analysis concludes that increased evaporation on Lakes Michigan and Huron are largely being offset by increases in local precipitation. This is why the IJC and Corps take the position that natural causes (“Mother Nature”) is to blame for low lake levels, not human-induced climate change. Because the lakes are still fluctuating within their normal range and the potential exists for higher water levels, expensive mitigation schemes have not been considered feasible as of yet. This may change if the lakes don’t return to more normal levels, and the economic consequences mount.

      While much was learned with their state-of-the-art climate research, the two agencies admit that the dynamics are still poorly understood. Using global models to understand what’s going on at the regional or local scale is problematic. Further complicating matters, they have not been able to reconcile model results with historical data (see link below), which indicates that lake levels tend to be lower during warmer climate regimes and higher during cooler climate regimes in the past.

      The latest research (described above) sheds further light on the complex interactions among lake temperature, evaporation and ice cover. The lakes themselves are perhaps the best indicator of what’s going on around them. The lakes are warming, evaporation is increasing and lake levels remain below normal. If these trends continue, it would add urgency to the need to re-evaluate mitigation measures, not detract from it. Furthermore, solutions that don’t take into account potential changes due to climate may not be adequate. This is why an adaptive approach to management is being recommended for future Great Lakes restoration activities.

  • Jason

    While this is a good article, I think Bob’s comment has merit and Lisa’s out of hand dismissal of it is an inherent problem in these calculations. Estimates of evaporation rates are interesting but can hardly be validated. In addition it doesn’t account for the water vapor that that immediately gets re-absorbed back into the lake. 29billion gallons per day sounds like a lot and it is. But it is a theoretical number that can’t be directly verified. What can be directly measured is the 210million gallons of water taken out of a single well every year. That is one well pumping at 400gallons per minute (not the fastest pump there is by the way!). Now that number sounds like just a small portion of the evaporation, but it is something we can directly measure and directly impacts the return flow of water into the lakes. Add this up for all the wells currently pumping water and you have a larger impact. Now if you look at the aquifer under the land mass as a sponge, the levels of pumping have a very great effect on the water flowing into the lake because the rainfall onto the land mass is now going to fill the emptied aquifer rather than runoff to the lakes. This is a very large factor because the area of land mass we are talking about makes the surface area of Superior seem insignificant in comparison. This is clearly a complex system and all parts of the system have to be taken seriously.

    • Thanks for your comment. It gives me the opportunity to clarify that my response to Bob’s comment was in no way intended as a dismissal of the issue regarding withdrawing water from aquifers for bottled water. The types of withdrawals that you and he describe can have major impacts on groundwater and inland lakes, rivers and streams. The Great Lakes ecosystem is a complex system and water withdrawals are an important issue for the future of both surface and groundwater.

      You may be interested in this 2000 report on the Protection of Waters of the Great Lakes: http://www.ijc.org/php/publications/html/finalreport.html#3. Although these data are more than ten years old, the report looks at the impact of bottled water. At that time, about 14 times more bottled water was being imported than exported from the Great Lakes Basin. The net effect of imports and exports doesn’t address the point you make about impacts on individual aquifers, but this is the reason the report concludes that “bottled water appears to have no effect on water levels in the Great Lakes Basin as a whole.”

      In my reply to Bob, I provided information about the volume of water lost through evaporation to illustrate its significance to net basin supply in comparison to bottled water. The original post explains in more detail that the impact of evaporation is no longer based on estimates. Researchers are now measuring (rather than estimating) evaporation on all five of the Great Lakes. Their measurements and observations confirm the significance of evaporation and help explain some (not all) of the complex interactions among factors that affect water levels.

  • mr B

    you can,t drink oil you can,t eat gold it,s all about greed till the end

  • Jon

    I remember well the low water in 1964. It was a novelty to beach on exposed shoals. There was no cable, no internet, and no hysteria. It was a clear hot summer. Everyone agreed it was Chicago’s fault.

  • John Lenters

    In reply to Jason, and to confirm what Lisa has said, the evaporation rates that she’s quoted are not just “theoretical estimates.” These are measurements … i.e., real observations. We’ve deployed meteorological stations on the lakes that measure the rate of water vapor loss to the atmosphere (i.e., evaporation), and these numbers can be … and have been … verified with other measurements, such as the lake water balance (precipitation, change in lake level, etc.). So the 29 billion gallons per day of evaporation is both a large number and a “real measurement.”

  • Doug

    Even if Al Gore is right, with nearly 7 billion people in the world and growing, we’ll need to do a lot of convincing and we’ll need to do it quickly. Good luck with that. I can’t convince my kids to turn off a light switch when they leave a room. Has anyone convinced AG to park his jet? Like some of the other commentators I’m old enough to remember hot dry years and people piling sand bags in their yards to hold Lake St. Clair back in other years. As a wise old man once told me, it sure is pretty to look at but you’re always fightin’ her. I remember Lake Erie catching on fire too and the gov stepped in and did it’s job. C’mon though really? A carbon footprint tax? Just like the northern MI water that finds it’s way into plastic bottles in the name of profit, I’m sure carbon tax revenues will ironically find there way into the grants that support research and articles like this one. Not that it’s bad to study this and learn but in the life span of the rock we’re living on, modern man has been here about a nano second. How much do we really know? But let’s suppose this article is right. At the end of the day it comes down to economics. It always does. Whose going to fund it all my friends? We clearly can’t pay the bills we have and you’re never going to convince the generation of kids now entering the workforce to unplug from the grid, to walk to work instead of drive, or to live with less than what my parents or grandparents had.

  • Richard Luis

    the best thing i havent read.

  • Mike Hubbert

    Better late than never in reading one of the first sane articles that I’ve seen.
    To all your detractors, please be aware that one of the first churchs on the lake was St Felicity which was established in 1826. It was flooded out in1836 and again in1855 at which time the waters did not recede and the parish and cemetery were abandoned.
    Around this same time, 1835, the town of Belvidere was established at the mouth of the Clinton River .By 1837 there were 20 buildings and in 1838 the Bank of Lake St Clair was organized. By 1839 the whole town was six feet underwater and abandoned.
    I submit that the “Historic Levels” of these waters are highly suspect

  • Terry

    Yep, this story is loaded with crap. We are flooding everywhere and the lake is still lower than ever. WTF is going on with our Superior? It looks about 5 or 6 feet lower than what it used to be.

  • Psalmon

    As of now Superior, Erie and Ontario are at normal levels.

    Only Huron and Michigan are below average. However H&M are not controlled and dredging, Chicago River reversals and other past moves lowered the lake level by 16 inches. So based on that H&M are normal too.

    Check it out here: http://www.glerl.noaa.gov/data/now/wlevels/levels.html

    The sky isn’t falling and neither are the Lakes.

    • Lake levels have been on the rise these past few months with much needed rain, but we’re not out of the woods just yet. Lake Erie has not been affected as much by low water levels, and Lake Ontario’s water level is regulated at its outlet. Lakes Superior, Michigan and Huron continue to remain below their long-term averages. This has been the trend for nearly 15 years, and although the lakes will continue to fluctuate seasonally and from one year to the next, it is this longer term trend that is of concern when considering the impacts of climate change. Forecasters predict that it will take several years of wetter than normal weather to restore water levels in the upper lakes. And to remain there, this will have to offset climate-related trends such as warming water temperatures, loss of ice cover and increased evaporation rates, not to mention the increase in droughts and heat waves — all of which are contributing factors to low water levels and cause for other concerns about the ecological health of the lakes.

      The downside to all of the rain is another disturbing climate-related trend: the increase in extreme rain events that contribute to flooding (earlier this year in the western portion of the Great Lakes basin) and harmful algae blooms (in Lake Erie in 2011). The sky isn’t falling, but the Great Lakes are not immune to the impacts of human-induced climate change either.

  • OJ Simpson

    It’ now August 2014 lake levels are above normal and water temps are a bone chilling 6-7 degrees below normal. Global warming is a fraud people need to wake up and stop believing the propaganda.

    • OJ, Thanks for your comment. I assume that you’re referring to Lake Superior, and if so, you’re right that water levels are (finally) above normal. But to put this in perspective, it’s the first time the water levels have exceeded the long-term average since 1998. There is natural variability with lake level fluctuations, and what’s alarming about this most recent period is the length of time (more than 15 years) that the lakes remained below “normal.” It’s the longest period of time that water levels remained below average since record keeping began almost 100 years ago. The cooler, wetter and icier conditions this past year contributed to the recovery of lake levels and are further evidence of the role of climatic factors. This past winter was more like the cold winters experienced in the late 1970s. For more information on how the cold winter affected summer water temps, see my post “Ice Cover Affects Lake Levels in Surprising Ways.” One or even several cold winters is not enough to declare global warming a “fraud.” This is all part of what I refer to as climate variability in the post.

  • Psalmon

    As of August 14 Lake Michigan Huron is now above normal:

    So, ALL of the Great Lakes levels are above normal. Not just for August either, MI HU is above July’s seasonal peak level now too. Since this article was published, MI HU is up 3 1/2 FEET.

    Lake Superior is up 2 1/2 feet during this period and now stands 6 inches above normal. For the year Superior will average 602 feet which is ABOVE the long term yearly averages for the Lake.

    On June 11 you responded: “It’s been more than just a few months of favorable conditions that has resulted in higher water levels on Lake Superior.”

    You’re talking out of three sides here: It’s long term climate change(low), It’s more than just a few months (high), It’s natural variability (short term discount of high).

    IN addition ALL Lakes are at below average temps too. So after another low evaporation Fall and and above average Ice Winter, levels will only continue to grow above average in 2015.

    Time to face facts. Stop discounting 2014 as some data point you can just throw out indiscriminately. The Lakes are at normal levels. Get out your camera and update your pictures at the least. Your credibility will be underwater as much as the shoreline pretty soon.

    • Psalmon, I provided examples (low and high water levels) to demonstrate the role of climate change and variability in fluctuating water levels. I am in no way discounting 2014 as an important year, but it’s just not a reason to dispute the main points of this post. In fact, it is further evidence of the importance of climate in lake level fluctuations. When conditions change, lake levels respond accordingly.

  • Betsy

    All the words form opinions generated by thoughts. Thinking is power, and that causes action. This is a stimulating and informative read. Thanks Lisa and all responders.

  • D Carter

    Interesting discussion on lake levels and climate impact.
    I think we can all agree on one thing, the climate is always changing always has and always will. The cover on Time Magazine in 1977 the experts predicted the coming of the next Ice Age, in 2006 Time Magazine cover the experts predicted the coming of Global Warming.
    Another thing we can all rely on is mankind’s memory loss every thirty years or so people forget the last set of experts and we can start the spin cycle all over. Love the debate.

  • Harry

    See the lake levels lately? Thus reasons why you people need to quit trying to blame every little thing on climate change. It is called natural variability.

    • Lisa Borre

      Harry, I actually saw the water level on Lake Michigan last weekend and was celebrating the rapid rise since the low point just over two years ago. I also attended the International Association of Great Lakes Research conference last month to get the latest update. There is now scientific consensus that the period between 1998-2013 was not consistent with “natural variability,” and the two years since, has also been unusual from the standpoint of the most rapid rise in water levels ever recorded. You may chose to deny that climate change is having real impacts on the Great Lakes, but for the sake of the Great Lakes, I don’t share your views. Let’s hope that the lakes have recovered enough before another warm period negatively affects water levels.

  • Chris Lamm

    Great Lakes Go from ‘Climate Change-Induced’ Low Water Levels to Record Highs in 3 Years.

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