Pennsylvania senators have an opportunity right now to provide unprecedented protection for North America's Great Lakes.

The five lakes are the largest surface freshwater system on Earth, containing 84 percent of North America's supply and 21 percent of the world's. Only the polar ice caps contain more.

The Great Lakes-St. Lawrence River Basin is 700 miles wide and 900 miles long and, according to the Environmental Protection Agency, is home to 30 million people, 7 percent of American farm production and a quarter of Canada's agricultural production.

This resource, while vast, is neither infinite nor entirely renewable, and it is vulnerable to threats from a range of pollutants. Health and economic vitality are dependent on the watershed.

That's why, after nearly five years of negotiations, the premiers of Ontario and Quebec and governors of eight states along the lakes endorsed a water resources compact in 2005. Since then, the terms have been adopted by Illinois, Indiana, Minnesota, New York, Ohio, Wisconsin and Michigan. That leaves only Pennsylvania to agree before the plan can go to Congress.

The state House unanimously adopted House Bill 1705 in January, and the matter now is before the Senate. It would prohibit, with rare exceptions, shipping Great Lakes water outside the system's vast drainage basin. States must develop water conservation measures and promote environmentally sound policies that are economically feasible.

A decade ago, a threat to the lakes came from a Canadian firm that wanted to ship tankers of Lake Superior water to Asia. The company dropped its plan in the face of widespread criticism, but the action pointed out the need for stronger protections.

The worldwide demand for fresh water is growing exponentially, and Lake Erie continues to be the lifeblood of Pennsylvania communities. This natural resource must be preserved. We can't live without it.