The watershed of Lake Erie's western basin encompasses several million acres of land in the U.S. states of Michigan, Ohio, and Indiana as well as the Canadian province of Ontario. Over two million people live in the watershed, in the cities of Detroit, Toledo, Fort Wayne, and London, Ontario. The watershed drains large swathes of agricultural land as well as several major metropolitan areas.
The score of the Western Lake Erie watershed was calculated from ten indicators with adequate data. You can read more about the individual indicator scores here.