Onaping Lake

Where Onaping Lake is

Onaping Lake lies in the District of Sudbury.

How deep is Onaping Lake?

The deepest mapped contour on Onaping Lake is 48.8 meters, and the water within that boundary descends even farther. Ontario’s bathymetry record holds 323 depth contours for Onaping Lake.

See also Ontario's Largest and Deepest Lakes

Surveyed Depths

Ontario has surveyed the depths of several thousand of its lakes over more than half a century. Later surveys were conducted by boat with satellite positioning and produced hundreds of thousands of soundings per lake. Earlier surveys were charted by running transects across the water and drawing depth contours by hand.

Water quality

Ontario’s Lake Partner Program is a volunteer monitoring network. Participants collect water samples for phosphorus analysis and measure water clarity through the summer with a Secchi disk. Most sites are sampled for phosphorus once a year, in spring, and some several times a year between spring and fall. Phosphorus in many lakes rises through the summer, so the two kinds of average are measured on different bases.

Phosphorus is the nutrient that controls how much algae a lake can grow. A lake with little phosphorus stays clear and supports cold-water fish such as lake trout. As phosphorus rises, algae increase, the water clouds, and oxygen in the deep water falls as the algae decay. The province classifies each monitoring site by its average phosphorus:

• Oligotrophic, below 10 micrograms per litre: clear water and low algae.
• Mesotrophic, from 10 to 20: moderately productive water, with more algae and weed growth than an oligotrophic lake but rarely a bloom.
• Eutrophic, above 20: nutrient-rich water, prone to algal blooms and low oxygen at depth.

Onaping Lake has 5 Lake Partner monitoring sites. Two have reported phosphorus for the three or more years the province requires before a status is assigned. All are classified oligotrophic.

The longest record is held by site 4156/2 at Big Water, with phosphorus sampled once a year over 5 years to 2025. Its long-term mean phosphorus concentration is 7.62 micrograms per litre, within the oligotrophic band, which extends to 10.

A Secchi disk is a white or black-and-white plate lowered on a marked line until it disappears from view. The depth at which it vanishes is the Secchi depth, a direct measure of water clarity. Clearer water gives a deeper reading.

The 39 clarity readings at site 4156/2 give a median Secchi depth of 3.6 meters.

Median Secchi depth by year at site 4156/2

See also Lake Water Quality and Blue-Green Algae in Ontario

Onaping Lake Weather

The weather page for Onaping Lake carries the forecast over the water, wave heights across the lake, and the modelled water temperature.

Onaping Lake weather

Water temperature

Ontario’s aquatic resource records class Onaping Lake as a warm-water lake.

A lake separates into layers through the summer where it is deep enough. Sunlight and wind warm and mix the upper few meters, and beneath a band of rapid cooling, the thermocline, the water stays cold. A shallow lake mixes to the bottom instead and warms through, sooner in spring and later into autumn.

No provincial monitoring station records water temperature on Onaping Lake. The LastLake model computes the temperature of its surface water for each day from the daily mean air temperature at Environment Canada’s Sudbury Climate climate station, 72 kilometers from the lake, or the next nearest station when its record is incomplete, and from the lake’s area of 6,689 hectares and its mean depth. The province’s records give no mean depth for Onaping Lake; the model uses 7.5 meters, estimated from the lake’s depth contours.

Each day’s figure carries the model’s typical error for that month on lakes of the same size. The figure in the chart below is the temperature near the surface, away from the shoreline. Bays, shallows and water deeper below the surface differ in temperature. Temperature is not measured when ice covers the lake. The weather page for Onaping Lake carries the model’s figures for the past weeks and the coming week.

See also Lake Water Temperature in Ontario

Fish in Onaping Lake

Ontario’s aquatic resource records list no species for Onaping Lake. The province’s other records for the lake name eight species, among them walleye, burbot and northern pike. They appear in the records below.

Popular species in the province’s records

• Northern Pikepike
• Walleyeperch
• Smallmouth Basssunfish
• Burbotcod

Spawning areas

Ontario maps 2 fish spawning records within the Onaping Lake outline: 2 walleye spawning areas covering 12.93 hectares.

By number of records

By area mapped

• Walleye2 areas12.9 ha

The federal Fisheries Act prohibits the harmful alteration, disruption or destruction of fish habitat without an authorization, so a dock, dredging, infill or shoreline work at a mapped spawning area is reviewed on that basis.

Stocking history

Ontario’s stocking records for Onaping Lake run from 1947 to 2014 and hold 55 releases. Walleye account for most of the fish: 1,476,206 released in ten of the years between 1949 and 2010. The last recorded release was 6,584 lake trout yearlings in 2014.

Eating the fish

The 2026 Guide to Eating Ontario Fish carries consumption advice for four species taken from Onaping Lake, tested for contaminants at a sampling location in Emo & Fairbairn Twps., Sudbury Dist. Each figure below is the most meals a month the guide advises for a fish of that length. Where mercury sets the advice, the figure falls as the fish gets longer, because mercury accumulates over a fish’s life. A zero means the guide advises no meals of that fish at that size.

General population: adultsSensitive population: children under fifteen, women who are or may become pregnant

Fisheries Management Zone 10

Onaping Lake lies in Fisheries Management Zone 10. Ontario sets its fishing seasons and catch limits by zone.

Fisheries management zones around Onaping Lake

Where a row reads zone-wide, the zone’s own season or limit above applies.

See also Fishing Seasons in Ontario, Zone by Zone and Fish Stocking in Ontario Lakes

Onaping Lake Ice Fishing

An ice hut on Onaping Lake must be removed by March 31. The province sets dates for ice hut removal as a safety measure to ensure huts are removed before thawing occurs. One date applies to an entire fisheries management zone (FMZ). Onaping Lake lies within FMZ 10.

An ice hut must also be removed before the ice breaks up, whether or not that date has passed. The deadline clears huts from the ice ahead of the thaw and does not close the fishing season.

Registration is required in FMZ 10 for an ice hut built of anything other than fabric, and for a fabric tent covering seven square meters or more. Registration is free, and the number is displayed on the outside of the hut.

Ice conditions

No public record reports the thickness or the condition of the ice on Onaping Lake on any given day. Ontario publishes ice safety guidance for anyone going out on the ice, at ontario.ca.

See also Lake Ice in Ontario and When the Lakes Will Freeze This Winter

Islands and names

Onaping Lake contains 426 islands in the Ontario Hydro Network’s outline, 21 of them over 10 hectares and 222 under a tenth of a hectare.

Official names

Ontario’s geographic names register lists 12 official names on the water and its islands: six bays and two narrows.

Bays 6

• Arrow Bay
• East Bay
• Green Bay
• Loon Bay
• Muldrew Bay
• Turcotte Bay

Harbours, cuts and narrows 2

• Poplar Narrows
• Three Mile Narrows

Nearby lakes

• Windy Lake51 km away
• Vermilion Lake59 km away
• Fairbank Lake66 km away
• Wanapitei Lake68 km away

All lakes

Questions about Onaping Lake

• How deep is Onaping Lake?

  Its deepest charted contour is 48.8 meters, and the water within it is deeper.

• How big is Onaping Lake?

  Its surface covers 66.9 square kilometers and it holds 426 islands. Of its 619 kilometers of shoreline, 408 kilometers is the mainland shore and 211 kilometers is the shore of the islands.

• Is the water clear?

  All two monitoring sites with a phosphorus status are classified oligotrophic, the clearest of the province’s three bands.