Lake Ontario, United States and Canada

Lake Ontario is one of the 5 Great Lakes in North America, along with Lake Superior, Michigan, Huron and Erie. The lake complex is an important part of North America’s cultural and physical heritage. The lake is the smallest of the five in terms of surface area, but still it is the 14th largest lake on our Planet.

Lake Ontario Stats

Lake NameLake Ontario
CountryUnited States
Surface area19347.360
Maximum depth244.0
Average depth84.8
Lake typeGlacial
Catchment area766137.40
InflowsNiagara River
OutflowsSt Lawrence River
Shore length2609.93
SettlementsToronto, Hamilton, Rochester
Residence time2450.5
FrozenJanuary to April
Dam height20
Dam year1958
Average discharge7745.819

Geography and Hydrology

The vast freshwater lakes provide water not only for consumption, but also for transportation, recreation and power in the area. For the early settlers, they provided the gateway for penetrating into the heart of the continent.

Lake Ontario is situated at the border of the two largest North-American countries, with a surface area of 19,000 km2. Canada’s most populous province was actually named after the lake. Ontario is the Easternmost of the Great Lakes, being the only one that does not share a coastline with the state of Michigan. The water from the four other lakes flows through Lake Ontario, which serves as an outlet to the Atlantic Ocean through the Saint Lawrence River.

A lot of rivers contribute to Lake Ontario, of which Niagara River is the largest. Among other inflows we can enumerate the Don, Humber, Trent and the Genesee rivers. The water’s levels are under continuous change, depending on the seasonal differences of its inflows and the trend in local precipitation.

As a result of long-shore drifts, baymouth bars appeared and created a large number of lagoons and bays on the lake’s shores. The most popular is the Toronto bay, which was elected the capital of Upper Canada, thanks to its strategic harbor. Hamilton harbor, Sodus bay and Irondequoit bay are also similarly conceived bays. These bars are also home to long sand beaches such as Sandbanks Provincial Park and Sandy Island Beach State Park.

Alongside these sandy areas one can often encounter wetlands, which are home to rich plant and animal life, also serving as stopping and feeding points for various migratory birds. One of the places with the richest biodiversity, with wetlands and rare aquatic plants, is the Bay of Quinte, which isolates the Ontario mainland from Prince Edward County.

There are plenty of islands on Lake Ontario, lying mainly on its Eastern and North-Eastern shores. Wolfe Island is the largest, and is accessible by local ferry rides from the Canadian and the American as well. Other important islands are the Toronto islands, Association island, Galloo, Simcoe and Garden islands.

Formation of Lake Ontario

Lake Ontario’s basin was sculpted out during the last ice age by the Wisconsin ice sheet. The large amount of materials and sediments pushed to the South by the ice sheet have created various formations like drumlins, kames and moraines on the new land surface, and at the lake bottom. This action has reorganized the precinct’s drainage system.

Whilst the ice sheet was retreating to the North, it clogged the outlet of the Saint Lawrence Valley, which means that the lake was once situated at a much higher level. This stage was known as Lake Iroquois. Lake Ontario later drained right through today’s Syracuse area, into the Mohawk River, and then reached the Hudson River, and its final draining point, the Atlantic Ocean. The shoreline which proves this motion can still be seen at the beaches, 20-40 kilometers from the lake’s shoreline today.

When the ice finally retreated from Saint Lawrence Valley, the outlet was below sea level for a short period of time, so the lake actually became a temporary bay of the Atlantic Ocean. Progressively, the land managed to overcome from the ice that released it. The lake bed is still tilting towards the South, inundating its shores, converting river valleys into bays. Lake Ontario’s Northern and Southern shores experience shoreline erosion.


Because of the lake’s depth, it can never totally freeze during the winter cold. It usually develops an ice sheet between 10% and 90%, mainly along the coastline and the many bays, where the water is a little shallower. When the winter is not too severe, ¼ of the lake’s surface area is usually covered in ice. Ontario was nearly totally frozen for 5 times (which have been recorded), the last time was more than 80 years ago, in 1934.

The lake is home to interesting natural phenomena, when the shores are referred to as snowbelt. It occurs when the cold winter winds pass over the warmer areas of the lake, picking up moisture and carrying it, dropping it off later as lake-effect snow. The area between Oswego and Pulaski receives nearly 600 centimeters of snow because of this action in some winters. The Tug Hill Plateau also receives some of this type of snow, and has become a popular location for winter sports enthusiasts like cross-country skiers and snow-mobilers. The lake-effect snow can even reach up to the town of Syracuse.

Because of the lake’s microclimatic effects in the summer months, fruit production is a very popular agricultural activity, especially on its South-Western shores. Some of the most popular fruit orchards include apple, cherry, pear, plum and peach. The climate is also fit for vineyards to blossom, so there are plenty of wineries around Lake Ontario.


In pre-European times the large lake served as the border between the Huron and the Iroquois people. Iroquois were the first nation to inhabit the lake area. In the 1600s the Iroquois bundled off the Huron people and settled in their place.

The first documented European arrival was in 1615, when Etienne Brule, a Frenchman arrived to Lake Ontario and named it Lac de Saint Louis. In 1660 a Jesuit historian, Francis Creuxius, came up with the name “Lacus Ontarius”, but a 1712 French Map shows that the name of the lake in that period was Lac Frontenac, after a French soldier.

A large number of trading posts were put up by British and French settlers, such as Fort Frontenac (1673), Fort Oswego (1722), and Fort Rouille (1750). After the French and Indian war ended in 1763, all of these trading posts were handed over to the Brits.

The population centers around Lake Ontario are between the oldest that can be found in the Great Lake Basin. Kingston dates back to 1670.

The lake became the heart of commercial activity following the war of 1812. The streamer activity in the area reached its peak in the 19th century, before the railways took over its leading position.

Settlements and Activities on the Lake

The lake shores are home to massive conurbations and cities, part of the Golden Horseshoe, situated on the lake’s Western coast. This region is anchored by Toronto, the provincial capital, and Hamilton.

The Canadian part houses the largest cities on the lakeshores, such as St. Catharines, Oshawa, Cobourg and Kingston, while the American part also has a few cities (Rochester), but is mainly a more rural area. Other smaller, but important cities are Whitby, Mississauga, and Burlington. Nearly 9 million Canadians live on the watershed of Lake Ontario, together with 2 million Americans.

The main human activity practiced on the lake is navigation, which is extremely important, since all the lakes’ rivers go through Lake Ontario, heading towards the Atlantic Ocean via the Saint Lawrence Seaway. Another similarly important waterway is the Trent-Severn waterway, connecting Ontario to Lake Huron at Georgian Bay.  The Oswego canal joins the lake to the New York State Canal System.

The lake’s coastline is home to many lighthouses, of which we can enumerate Beach Canal Lighthouse, Braddock Point Light, Gibraltar Point Light, and the Oswego Harbor West Pierhead Light.

Industrialization, Environmental Issues and Ecology

Lake Ontario was once an important fishery center, but because of the negative effects of overfishing, water pollution and the introduction of various invasive species into the lake, nowadays only recreational fishing is permitted on its premises.

Thanks to its size and the diversity of the many animal and plant species existing in and around its waters, Lake Ontario is considered by many an ecological wonder.

The lake is home to many aquatic plants, of which some depend on low water levels to reproduce. However, due to the diversity of water fluctuations, the lake’s level is continuously changing, hurting plants such as the meadow marsh.

Lake Ontario’s shores are mainly populated by deciduous forests, mainly maple, oak, beech, ash and basswood trees. Because of a massive deforestation wave, the local ecosystem has suffered drastic consequences. Many trees were cut down, which led to the loss of forest birds, extinction of the native Salmon and an increase of sediment and waste flowing right into the lake. In some areas over 90% of the trees were cut down, only to be replaced by agricultural lands.

The open water wasn’t so much affected by the deforestation of its shores. It was, however, troubled thanks to the nutrient levels which control the production of Algae, which is practically the basis of underwater life. Because of various, damaging human activities, 10 fish species have gone extinct, while 15 exotic species were brought in to the lake, affecting the ecosystem of its waters. The Lake Sturgeon, a native fish of which there were plenty in 1860 became nearly extinct by 1960.

Lake Ontario was also heavily damaged by the pollution coming from various factories, industrial chemicals, sewage draining into the lake, laundry detergents, pesticides used on agricultural grounds and fertilizers.

The ‘60s and ‘70s witnessed abundance in Algae blooms, which caused the death of a large amount of fish. These blooms became so thick, that the waves couldn’t even break on them. The birds that ate the sick fish (the Osprey, Bald Eagle and Cormorant) also got poisoned. After these unfortunate events, some efforts have been made to increase public awareness, lower the effect of heavily industrialized areas and restore natural habitats in and around Lake Ontario.

In the late ‘80s, 43 areas were selected and proclaimed as “Areas of Concern”. Out of these, 7 are situated in Lake Ontario’s precinct: Bay of Quinte, Eighteen Mile Creek, Hamilton Harbor, Metro Toronto, Oswego River, Port Hope Harbor and Rochester Embayment. The lake managed to recover some of its pristine, natural areas.

The Walleye reappeared in Ontario, a fish, which marks the cleanliness of a lake’s waters. Because of the increase of sport fisheries, new fish species were introduced, such as the Coho and the Chinook salmon; however invasive species like the Lamprey and the Zebra mussels still remain a serious issue.

Today’s great threats remain the fast development of urban areas, generation of electricity towards these places and the sewage pollution.

Fun Facts

In the 1800s a legend has circulated among those living on the shores of Lake Ontario about a creature similar to the Loch Ness Monster of Scotland. It supposedly had a long neck, was green and caused a break in the surface of the waters.

Lake Ontario has a “seiche”, which is a natural rhythmic motion similar to waves, when the water wallows back and forth every 11 minutes. The lake has a retention time of 6 years, while its waters get from one end to the other.

The Niagara Falls pours into the lake, in which the most popular fish used to be the American Eel, before overfishing occurred.

Swimming across the lake has been considered a great challenge in the past hundred years. As of 2012, nearly 50 people swam across Lake Ontario, of which the youngest was a 14-year old girl, who made her 52-kilometer way in less than 27 hours, from the town of Niagara-on-the-Lake to Marilyn Bell Park.

There is a scenic road connecting all Great Lakes, called the Great Lakes Circle Tour and Seaway trail, offering amazing views over the freshwater lakes and their surroundings. The New York State Seaway Trail is a similar 730-kilometers scenic trail, encompassing Lake Erie, the Niagara River, Lake Ontario and the Saint Lawrence River.

Tourism and Leisure

Lake Ontario has more than 100 beaches; some are among the best beaches in North America. Sandbank Provincial Park in Prince Edward County is home to one of the largest freshwater Dune systems on the Planet.

One of the main activities practiced on the lake is fishing. Rochester basin is one of the best fishing spots on Lake Ontario, where one can catch Salmon, Steelhead, Brown trout and Lake trout. In this area, between the months of June and August, fishermen usually catch the largest predatory fish, which consist mainly of Chinook salmon and King salmon.

Other popular activities include hiking, canoeing, backpacking, bird-watching and sailing.

Lake Ontario Map