Canada has 20 percent of the world's known fresh water supplies. Over the years there have been various proposals by U.S. interests to import some of it to the American Midwest and Southwest. But that has not happened, partly because Canadians oppose exporting their water.

• Recently, entrepreneurs have suggested shipping fresh water from Canada to the U.S. -- utilizing freshly- scrubbed, single-hull oil tankers, which can no longer legally be used to transport oil.

• But the Canadian government has imposed a temporary ban on bulk fresh water exports.

• The moratorium will be in place until all 10 provinces -- which share jurisdiction over lakes and rivers with the federal government -- can come up with a plan to ban water exports permanently.

• But bulk fresh water could become a commercial good covered by the provisions of the North American Free Trade Agreement if an export permit is issued by a single Canadian province.

Similarly, any attempt to ban water exports would actually acknowledge that fresh water in lakes and rivers is a commodity and bring it under trade-agreement regulations, experts point out.

Meanwhile, vast quantities of pristine water continue to flow unchecked into the Atlantic and Pacific oceans.

Source: Anthony DePalma, "Free Trade in Fresh Water? Canada Says No," New York Times, March 7, 1999.