Is Lake Ontario Saltwater or Freshwater?

Lake Ontario is a freshwater lake. Lake Ontario is not saltwater.

Lake Ontario is Freshwater

Lake Ontario is a freshwater lake. How does a body of water qualify as freshwater?

What is Freshwater?

Definitions for freshwater differ. The Groundwater Foundation defines freshwater as water containing less than 500 parts per million (ppm) dissolved salts (source). The American Meteorological Foundation defines freshwater as water containing less than 1000 ppm dissolved solids, a definition that includes other materials besides salt (source).

Lake Ontario is Freshwater

By either definition, Lake Ontario is freshwater and is not saltwater. The water in Lake Ontario has about 15 ppm dissolved salts. This means that Lake Ontario is a freshwater body of water.

Lake Ontario is not Saltwater

Because Lake Ontario is a freshwater body of water, by definition it is not a saltwater body of water. This is the case for all of the Great Lakes, which are all freshwater bodies of water.

shoreline. Superimposed text reads: Is Lake Ontario saltwater or freshwater?

The Salinity of the Great Lakes is Increasing

Even though Lake Ontario’s salinity is far below the threshold necessary to be considered freshwater, scientists are concerned that the salinity of the Great Lakes is increasing. For example, it seems that the salinity of Lake Michigan has  increased 7 times over the last 200 years (source).

The majority of that increase in salinity is attributable to road salt washing into tributaries of Lake Michigan and then passing into the lake itself. Lake Michigan is heavily settled, especially along its shores that border Indiana, Illinois, and southern Wisconsin.

These areas have harsh winters with plenty of snowfall and ice, meaning that road crews often use much salt to keep travel safe. While that road safety is certainly a benefit, it has come at a cost to the salinity of Lake Michigan.

While the Great Lakes have a long way to go before becoming saltwater seas, scientists are concerned that increased salinity will have poor outcomes for public health and for fragile ecosystems.

The Great Lakes of North America

The Great Lakes of North America are one of the world’s largest freshwater reserves, containing 21 percent of the world’s freshwater and 84 percent of North America’s freshwater. They are one of North America’s easiest identifiable features from space. They are important for shipping and recreation.

They supply drinking water. For example, much of Chicago’s drinking water comes from Lake Michigan. However, they supply a relatively small amount of drinking water in the United States as a whole.

The five Great Lakes of North America are:

Lake Ontario

Lake Ontario is the smallest of North America’s five great lakes by surface area. However, it exceeds Lake Erie in water volume.

It lies along the border between the United States of America and Canada. The Canadian province of Ontario and the U.S. State of New York have shorelines along Lake Ontario.

Major cities on Lake Ontario include:

  • Toronto, Ontario
  • Mississauga, Ontario
  • Rochester, New York

The Great Lakes of Africa

North America is not the only continent with a region of huge, freshwater lakes. This might surprise many people, but Africa also has a Great Lakes region. The Great Rift area of East Africa has ten large lakes containing about 25 percent of the world’s unfrozen fresh water.

The Great Lakes of Africa include:

  • Lake Victoria
  • Lake Kyoga
  • Lake Albert
  • Lake Edward
  • Lake Tanganyika
  • Lake Kivu
  • Lake Mweru
  • Lake Malawi
  • Lake Turkana
  • Lake Rukwa

Lake Baikal

Another large freshwater lake is Lake Baikal in southern Siberia of Russia. Even though Lake Baikal has a relatively small surface area, its great depth means that it holds 20 percent of the world’s unfrozen freshwater reserves. Lake Baikal has about 1,000 species that can be found nowhere else in the world. (Source)

List of the World’s Largest Freshwater Lakes

These are the world’s largest freshwater lakes, from largest to smallest:

  1. Lake Baikal
  2. Lake Tanganyika
  3. Lake Superior
  4. Lake Nyasa
  5. Lake Michigan
  6. Lake Huron
  7. Lake Victoria
  8. Great Bear Lake
  9. Great Slave Lake
  10. Lake Ontario
  11. Ladoga
  12. Titicaca
  13. Reindeer
  14. Helmand Erie


  • Lake Ontario is freshwater.
  • Lake Ontario is not saltwater.
  • The salinity of Lake Ontario is increasing due in large part to human activity.
  • Lake Ontario is one of the Great Lakes in North America.
  • There are other large freshwater lakes around the world.
About the author
Mark Stoneman
Hi! My name is Mark! I have been a resident of Door County for almost ten years now, and I'm glad to help you say "Hello" to Door County. I believe that travel helps to change lives, and because of that, I want to help you improve your life through travel.