The Great Lakes basin contains one fifth of the world's fresh water. About 35 million people use it as a source of potable water. Billions of dollars in economic activity – including a quarter of Canada's agriculture – depend on it.
So when a city outside the recognized boundaries of the watershed wins permission to tap into the lake system, it's a big deal.
Last week, Waukesha, Wis., did just that. Canadian politicians, mostly of the municipal variety, are up in arms about it. They are right to raise the alarm.
The Milwaukee suburb will draw about 30 million litres a day out of Lake Michigan, barely a drop relative to the 150 billion litres removed daily from the basin (overall consumption has been dropping since 2007). Most of it will be treated and returned.
The bigger issue is there have been a half-dozen significant diversions since the practice was ostensibly forbidden by mutual agreement in 1986.
Pumping water out of the Great Lakes is a serious enough issue that international agreements and strict conditions are in place to forestall it. Since 2008, every new project must be approved by the two provinces and eight U.S. states that front the lakes.
So why does it keep happening?
In a January report, the International Joint Commission that protects the lakes pointed out "it's important to remember there is no 'surplus' water" in the Great Lakes. Only one per cent is renewed each year by rain and melting snow. Average air and water temperatures are rising, scientists say, as a result of climate change. There is less ice in winter, more evaporation in summer.
The era of what the IJC calls "mega-diversions" has passed, and there is no appetite to allow bulk water exports. But the report also noted that "climate change or other unforeseen circumstances could conceivably change that calculus."
The 72,000 residents of Waukesha need clean water, and they will have it. But the guardians of our most precious resource should beware of setting precedents. North America is a thirsty continent, and it's becoming more parched every year.