Situated below Lake Huron, Erie's primary inlet is the Detroit River. The main natural outflow from the lake is via the Niagara River, which provides hydroelectric power to Canada and the U.S. as it spins huge turbines near Niagara Falls at Lewiston, New York and Queenston, Ontario. Some outflow occurs via the Welland Canal, part of the Saint Lawrence Seaway, which diverts water for ship passages from Port Colborne, Ontario on Lake Erie, to St. Catharines on Lake Ontario, an elevation difference of . Lake Erie's environmental health has been an ongoing concern for decades, with issues such as overfishing, pollution, algae blooms, and eutrophication generating headlines.