The Great Lakes – which supply nearly 20 million Americans with drinking water – are suffering from a major drought.
An unusually dry September coupled with the seasonal decline in water levels has caused levels to plummet between two to eight inches below the norm.
For Lake Superior, Lake Michigan and Lake Huron, this is the lowest they have been since 2014.
The Great Lakes, which span eight states, account for 21 percent of the world’s fresh water, and 10 percent of the US population relies on them for drinking water.
Lake Superior has seen the most drastic decline after receiving just 38 percent of the rain it normally receives in September.
As of October 11, the water level for Lake Superior was 601.57 feet, which is six inches below the long-term monthly average for October.
Above average September temperatures have also played a role in this drought as the heat has increased the amount of evaporation from the Great Lakes.
30 million people live along the Great Lakes’ roughly 4,500 miles of coastline, and rely on them for drinking water
The Great Lakes are the largest group of freshwater lakes in the world by total area, and the second largest by volume.
They span Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania and Wisconsin.
This isn’t the first time that the Great Lakes have suffered from drought. In 2013, water levels sank to all-time lows following a year of record-breaking high temperatures in 2012.
This had a major impact on tourism, fishing, local businesses and other industries tied to the lakes, with many harbor masters forced to resort to dredging to keep their harbors open.
Water levels could continue to decline until March, when spring rains and snowmelt offer some replenishment.
This corresponds to a seasonal decline that begins around September each year and lasts until early spring.
The Great Lakes rely on precipitation for replenishment. Each lake is surrounded by a drainage basin – an area of land where water from rain or snowmelt drains downhill into a body of water (in this case, the lake).
Of the five lakes, Lake Superior received the least amount of rain in September, at just 38 percent of normal precipitation, MLive.com reported.
The Great Lakes are the largest group of freshwater lakes in the world by total area, and the second largest by volume
This is the longest that Lake Superior’s water level has remained below the September monthly average since 2014.
Lake Michigan and Lake Huron – which are considered one lake when discussing water levels – have also fallen below the September monthly average for the first time since 2014.
This September, the Lake Michigan-Huron drainage basin saw hot, dry temperatures that drove increased evaporation, and only received 1.5 inches of rain – just 44 percent of the precipitation it usually gets.
Lake Ontario’s water level fluctuates the most among the five Great Lakes. That’s mainly because dams control some of the outflow from this lake into the St. Lawrence Seaway.
Right now, this lake is sitting at the long-term monthly average water level for September, and is expected to remain near normal over the next six months.
While Lake Ontario received the most rainfall in September, it still only got 80 percent of its normal rainfall.
Lake Erie’s water level is currently about eight inches higher than it’s long-term monthly average for September, but still only received 55 percent of normal rainfall that month. This lake’s water levels have remained normal since March 2015.
Climate scientists use the Great Lakes’ water levels as an indicator of climate change because their fluctuations are directly influenced by changing weather patterns.
Over the past several decades, water levels in the Great Lakes have undergone dramatic fluctuations, exhibiting a range of more than six feet, according to Michigan Technological University.
Water levels are determined by climate-induced alterations in three main factors: over-lake precipitation, lake evaporation and basin runoff.
Climate change has a direct effect on all three of these factors. In the near term, increasing temperatures associated with global warming make droughts like this one more likely.
But over the long term, scientists have predicted that climate change could cause the Great Lakes’ water levels to rise in the next three decades.
According to one study, the baseline lake level for Lake Superior, Michigan-Huron and Erie are expected to rise by roughly 8 to 20 inches by 2050 as a result of increasing precipitation driven by climate change.
This could cause serious problems for the more than 30 million people who live along the lakes’ roughly 4,500 miles of coastline – including densely populated cities like Chicago, Detroit and Buffalo.
Previous instances of record high water levels in the Great Lakes have already shown how resulting flooding can wreak havoc on infrastructure, communities and ecosystems.
