Low water levels in the Great Lakes and St. Lawrence River could result in severe economic fallout for the region, totalling more than $19.3 billion by 2050, according to a new report.

The basin has experienced the longest extended period of low water levels since the U.S. and Canada began tracking it in 1918.

The report, released Thursday by the Mowat Centre and Council of the Great Lakes Region, said water levels in the Great Lakes and St. Lawrence basin "fell dramatically" in 1997-98 and haven't recovered.

Mark Fisher, who heads the council, said there's a "very real future" where the region could be plagued by low-water trends.

"When you look at the last 13 years, we've gone through the longest period of low water levels in our history," he said.

Lake Michigan-Huron had the lowest water level ever recorded for the lake in January 2013.

Great Lakes' economic footprint is $5.25 trillion

The economic footprint of the Great Lakes Region is $5.25 trillion, or around 28 per cent of combined Canadian and U.S. economic activity.

The report said lower water levels in the Great Lakes — which hold about 20 per cent of the world's surface freshwater supply — would impact several industries, including:

Recreational boating and fishing: $12.86 billion.

Commercial shipping and harbours: $1.92 billion.

Hydroelectric generation: $2.93 billion.

Property values near the shores: $976 million.

Eighty-eight per cent of the losses for the recreational boating and fishing industry would result from losses in boating days and less spending on boating trips, equipment and maintenance or purchase.

The report speculates low water levels will force boaters to either not take their boats out or pay for costly repairs from using narrowing access channels.

Recreational boating also supports secondary industries like marinas, boat retail and equipment rental businesses, and tourism in small communities in the region. If the water levels drop by about 60 centimetres, the report says 29 marinas will be forced to close.

Also in that industry, increased days when sport fishing will be impossible and declining fish catch rates will cost the industry about $1.4 billion in the worst-case scenario.

Meanwhile, in the commercial shipping and harbour industry, loss of shipping capacity, harbour maintenance and repair costs and a smaller cargo capacity as boats sit lower in the water will form the bulk of the costs.

Indirect costs not calculated

The report added that while water levels have "rebounded" since 2013, due to factors including cooler temperatures in winter, it's "unclear" if this is the beginning of a trend.

"The general rule is that there is more evaporation and less precipitation, so less water in the system," Fisher said, explaining that only one per cent of the waters of the Great Lakes are renewed on an annual basis by precipitation.

He added that the study's projections are "conservative," given that researchers did not look at indirect effects or how low water levels could impact human health, commercial fishing or the manufacturing sector.

"The costs would only get much larger if we calculated in the indirect costs," he said.

Climate change is a closely related issue and requires input on local, provincial and federal levels, Fisher said, adding that U.S.-Canada collaboration will be essential to safeguard the future of the Great Lakes.

"The challenge that people have is (climate change) is gradual, it's incremental, it's hard to see," he said. "So when water levels go back up, they say the problem has gone away."

The next step is a cost-benefit analysis of adaptation measures and mitigation strategies in responding to climate-change induced low water levels, Fisher said.

"Climate change is real, it's happening today, the potential economic impact of climate change particularly on water levels is significant," he said. "We need to pay attention because at the end of the day, while the Great Lakes are vast, they are a finite resource."