Lake Ontario: Key Dimensions & Hydrology
Lake Ontario — the smallest by surface area but second deepest of the Great Lakes — is the outlet to the St. Lawrence River.
Vital Statistics
| Parameter | Value |
|---|
| Surface Area | 19,000 km² (7,340 sq mi) |
| Length | 311 km (193 mi) |
| Max Width | 85 km (53 mi) |
| Average Depth | 86 m (283 ft) |
| Maximum Depth | 244 m (802 ft) — near Rochester |
| Volume | 1,640 km³ (393 cu mi) |
| Shoreline | 1,146 km (712 mi) — incl. islands |
| Elevation | 74 m (243 ft) — lowest Great Lake |
| Retention Time | 6 years |
Hydrologic Role
- Inflow: 85% from Lake Erie via Niagara River (includes Falls).
- Outflow: St. Lawrence River (regulated by Moses-Saunders Dam).
- Stratification: Strong summer thermocline; deep water cold, anoxic risk.
- Seiches: Wind-driven water level oscillations (hours).
Ecology & Human Use
- Fishery: Lake trout, salmon (stocked), walleye, bass, yellow perch.
- Invasives: Zebra/quagga mussels, round goby, sea lamprey — altered food web.
- Cities: Toronto (N), Rochester (S), Kingston (E outlet).
- Water supply: 9M+ people (Toronto, Rochester, Syracuse).
Smallest Great Lake by area — but deep, dynamic, and the gateway to the Atlantic.
Wanderlust World