TRAVERSE CITY, Mich. — A US-Canadian panel urged both nations Friday to consider installing water retention structures to boost levels on Lake Huron and Lake Michigan, which fell to their lowest point on record in January and have lagged well below their historical average since the late 1990s.
The International Joint Commission, which advises the two federal governments about shared waterways, called for a study of placing inflatable gates or other devices in the St. Clair River, the outlet at the southern end of Lake Huron. Officials have acknowledged that dredging, gravel mining, and other human activities eroded the river bottom in the past century, accelerating the volume that flowed out of Lake Huron toward Lake Erie.
Owners of Huron shoreline property, particularly in Canada’s Georgian Bay, have demanded action for years to offset the losses, although federal scientists say rising evaporation and declining rain and snow are the biggest reasons for the lake’s drop-off.
In a letter to the governments, the commission proposed investigating ways to raise Huron and Michigan by 5 to 10 inches. Although considered two separate lakes, they are connected by a 5-mile-wide strait and are the same elevation above sea level.
‘‘Although future water levels are uncertain, we cannot ignore the damage’’ already done from record lows, said Joe Comuzzo, chairman of the Canadian delegation to the panel.
Although not endorsing specific measures, the panel suggested focusing on adjustable devices that could be activated during low-water periods when outflow from Lake Huron needs to be reduced, and deactivated when there’s danger that water could get too high.
The commission has six members, three from each country, although one of the Canadian positions is vacant. Four of them signed the report. Lana Pollack, head of the US delegation, declined to endorse it because she said it might give ‘‘false hopes’’ that artificial structures could solve the low-water problem.
While much of the document is praiseworthy, it understates the role climate change has played and says too little about the need for governments to help people adapt, she said.
‘‘The public really needs to understand what we’re doing to our Great Lakes by pumping greenhouse gases into the atmosphere and creating climate change,’’ Pollack said.
Great Lakes levels fluctuate seasonally and have risen and fallen significantly over the decades, but now are in a prolonged low-water period. Huron and Michigan have suffered the biggest drop-offs. When they set a record in January, they were 29 inches below their long-term average and had declined 17 inches within a year.
They have risen slightly since then, helped by heavy snowfall and rain. But the US Army Corps of Engineers says it would take a number of unusually wet years to restore the lakes to normal.
Studies have shown that Huron and Michigan fell by 10 to 16 inches because of dredging and other activities as late as the 1960s. Congress authorized steps to slow the flow from Lake Huron and the corps produced options in 1972, including miniature dams. But nothing was done because by then a three-decade-long rising trend was underway.
Mary Muter, codirector of a group called Restore Our Water International, said the commission’s support for boosting levels was ‘‘excellent news.’’ In addition to placing artificial devices in the river, the governments should spread rock rubble along the bottom to prevent further erosion, she said.
But another advocacy group, Georgian Bay Forever, said the proposal was ‘‘limited and ineffective.’’ It would not boost levels enough to help the shipping industry, which has lightened cargo loads to avoid running aground, executive director David Sweetnam said.