The Great Lakes were at record highs this summer, with all the lakes except Michigan and Huron – which scientists consider one lake – notching their highest monthly levels since record keeping started in 1918. And Michigan and Huron came within a fraction of an inch of their monthly records in June and July, 31 inches higher than the average over the last 100 years.
It’s a dramatic shift since just six years ago, when the lakes were at record lows, and people sold their boats and bemoaned their stranded docks. Today, the lake is about 6 feet deeper.
Scientists agree that water levels in the Great Lakes are cyclical, and it’s only a matter of time before the lakes draw down again. But the wild card is climate change, and experts say greater variations are possible and city planners and regular residents should plan accordingly.
Brammeier noted that fluctuating water levels are often good for species and habitat, creating wetlands and encouraging more biodiversity. But just like the very low levels, the high levels have caused angst for beachgoers, boaters, waterfront landowners and those who rely on lake-related tourism.
For Port Milwaukee, which contributes over $100 million to the regional economy annually, high water is nerve-wracking. Moderately high water is good for shipping, alleviating the urgency of the continuous dredging in the Great Lakes system, which links the Atlantic Ocean with the iron ore mines and grain fields of the North Country, via the St. Lawrence Seaway, the five Great Lakes and connecting rivers and canals.
But the lakes are now so high that the amount of water released from Lake Ontario into the St. Lawrence Seaway through the Moses-Saunders Dam has been increased to its highest sustained level ever. Increased flow into the seaway compounds that area’s own high-water problems and makes it harder for ships to come upstream. Shipping takes longer and uses more fuel, adding to costs.
If the flow is increased any more, shipping in the St. Lawrence Seaway could be shut down. That would be disastrous for economies that benefit from international Great Lakes shipping, according to Port Milwaukee Director Adam Schlicht. The port’s July volume – hundreds of tons of steel, salt, cement and other commodities – was up 12% over last year. “That progress would be hindered if the velocity of the dam [outflow] were increased,” Schlicht says. “Any increase [in the Lakes’ outflow] would have a draconian effect in Milwaukee.”
The Great Lakes’ water levels are determined by a fairly simple formula: the amount of water lost through evaporation and outflow into lower Great Lakes plus the amount of water coming in through rain, runoff and flow from the higher lake.
This spring saw record-setting precipitation, including the wettest May on the books in Chicago. Nationwide, the first five months of 2019 were the wettest such stretch in recorded history. A relatively cool spring also meant less evaporation.
Low lake levels six to seven years ago were driven by warmer water, meaning less ice and more evaporation. As lake levels started rising, extremely cold winters in 2013-15 meant extra ice cover – and less evaporation.
Chelsea Volpano is doing her master’s thesis at UW-Madison on sediment transport, quantifying the changes she’s seen firsthand since her childhood. “We have never seen the beaches this small or close to shore,” she says. “But it is cyclical. There’s definitely an adjustment period when the lakes are high, but the beaches will be back eventually.”
Like all Great Lakes, Lake Michigan’s water level fluctuates in a cycle. But within the past six years, the lake’s water level has hit a record low and come within an inch of its record high.