LAKE ONTARIO
The smallest of the Great Lakes, Lake Ontario borders New York and Ontario.
Lake Ontario contains 393 cubic miles of water and covers 7,340 square miles.
Lake Ontario has a drainage basin of almost 25,000 square miles. Forty-nine
percent of the basin is forested, 39% is used for agriculture, 7% is urbanized or
industrialized land, and the remaining 5% is used for other purposes. Lake
Ontario suffers from agricultural runoff and pollution. One of the greatest
stresses on the Lake is the regulation of water levels through mechanisms
comprising the St. Lawrence Seaway.
Like Lake Erie, the majority of water entering Lake Ontario is from the
upper lakes – about 85% of the average annual amount. Some 9% of the new
water entering Lake Ontario is from groundwater carried to the lake in
tributaries. Five percent is surface run off carried in tributaries. The net
contribution of precipitation accounts for nearly 2%. On an average basis,
approximately 251,000 cfs (or 162 billion gallons per day) leaves Lake Ontario
via the St. Lawrence River.