Lake Ontario

The Great Lakes and their watersheds span two countries and 8 US States! Lake Ontario is the easternmost of the five lakes with a majority of the watershed within NY state and Canada.

About the Lake  

Lake Ontario receives most of its inflow from the other Great Lakes (Superior, Michigan, Huron, Erie) via the Niagara River which flows into the western end of the lake.  The lake then drains through the St. Lawrence River into the Atlantic Ocean.  While it is the smallest of the Great Lakes when ranked by surface area (7,340 square miles; 18,960 square kilometers), it is the third deepest with a maximum depth of 802 feet/244 meters and an average depth of 283 feet/86 meters. Despite having a surface area similar to Lake Erie, Lake Ontario holds four times the volume of water. It has the second deepest average depth (Lake Superior has the deepest average and maximum depths) but has a water retention time of only 6 years.  

The Lake Ontario watershed covers about 24,720 square miles (about the size of the state of West Virginia). Within the state of New York, the watershed makes up nearly 20% of the entire state! Some major river watersheds that feed into the lake include the Genesee River, Oswego River (which receives water from the Finger Lakes) and the Black River. There are also many smaller tributaries along the Lake Ontario shoreline that are a part of its watershed.

History and Future  

Before French explorers arrived in Canada in the 1600s, Lake Ontario’s shores were home to the Haudenosaunee for thousands of years.  In the Wyandot (Huron) language, ontarío means “Lake of Shining Waters”.  Indigenous people maintained and thoughtfully utilized the land and its resources for many years.  As European immigrants began to settle in greater numbers in the watershed, settlers started exploiting the natural resources and bounty of the region by clear-cutting mature forests, plowing the land for agriculture, and indiscriminately harvesting fish populations from the lake.  

Over time, industrialization began to rapidly expand and waste water was discharged to nearby streams which ultimately flowed into Lake Ontario.  In addition to localized wastewater discharges, much of the pollutant load from the upstream Great Lakes continues to flow into Lake Ontario.  

In order to assess and monitor the ecosystem health of the lake, the state’s Department of Environmental Conservation and partners from neighboring states and Canada work together to create Lakewide Action and Management Plans (LAMPs). Theses plans are part of the efforts by the U.S. and Canada that were initiated through the Great Lakes Water Quality Agreement. This Agreement was initially signed in 1972 and has been updated several times over the past 50 years to ensure the Great Lakes' chemical, physical, and biological characteristics remain intact for generations to come. 

Resources and Links

• Lake Ontario Lakewide Action and Management Plans (LAMPS)

• About the Great Lakes Water Quality Agreement (GLWQA)

• New York Sea Grant's 2017 Lake Ontario Flood Story Map

• National Oceanic and Atmospheric Administration (NOAA) Great Lakes Lake Level Viewer

• Great Lakes Sea Grant Network Water Levels Resources