Now that nearly all the Great Lakes states have approved the Great Lakes Basin Water Resources Compact, it's time for Congress and the president to prepare to approve this agreement.

This treaty between the United States and Canada was approved by the Indiana General Assembly this year. It would establish important protections for the lakes that contain nearly one-fifth of the world's fresh surface water.

Lake Michigan is the source of drinking water for much of the region as well as a popular destination for boating and swimming. It is a giant lake, with an average depth of 279 feet.

Living in its shadow, the lake can easily be taken for granted. But elsewhere in the world -- even elsewhere in the nation -- long-term droughts make residents of those areas look longingly at the Great Lakes.

The Great Lakes Compact is essential in order to protect that water from being diverted elsewhere. Under the terms of the agreement, all of the states and provinces within the Great Lakes basin would have to approve any new diversion of water from the lakes.

States also would be required to adopt conservation plans and regulate their use of water from the Great Lakes and inland waterways.

U.S. Sens. Barack Obama and John McCain have both publicly supported the Great Lakes Compact. Congress must also support it.

Lake Michigan is our region's greatest natural resource. It is vital that the Great Lakes be protected through this treaty.