Thunder Lake

Where Thunder Lake is

Thunder Lake lies in the District of Kenora, with shoreline in the City of Dryden.

How deep is Thunder Lake?

The deepest mapped contour on Thunder Lake is 21.3 meters, and the water within that boundary descends even farther. Ontario’s bathymetry record holds 13 depth contours for Thunder 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.

Thunder Lake has 3 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 mesotrophic.

The longest record is held by site 5370/1 at TDR-1 Outflow at dam, with phosphorus sampled once a year over 4 years to 2022. Its long-term mean phosphorus concentration is 13.77 micrograms per litre, within the mesotrophic band, which runs from 10 to 20.

One reading at site 5370/1, 61.4 micrograms per litre on 11 May 2015, is left out of the site’s mean. The province’s published file includes it.

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.

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

Fish in Thunder Lake

Ontario’s aquatic resource records name 20 fish species in Thunder Lake. The province’s other records for the lake name one further species, brook trout. It appears in the records below.

Popular species in the province’s records

• Lake Trouttrout and whitefish
• Lake Whitefishtrout and whitefish
• Ciscotrout and whitefish
• Northern Pikepike
• Walleyeperch
• Yellow Perchperch
• Smallmouth Basssunfish
• Rock Basssunfish
• Burbotcod

Spawning areas

Ontario maps 18 fish spawning records within the Thunder Lake outline, for three different species, and all of them are mapped below. Every record is recorded as verified and presently suitable, and none is classed as sensitive.

By number of records

By area mapped

• Lake Whitefish16 areas36.3 ha
• White Sucker1 area3.8 ha
• Walleye1 area3.8 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 Thunder Lake run from 1948 to 1959 and hold 16 releases. Walleye account for most of the fish: 4,150,000 released in six of the years between 1950 and 1957. The last recorded release was 4,600 lake trout fingerlings in 1959.

The province’s record of stocking for recreational fishing, kept from 2016, lists no release into Thunder Lake.

Eating the fish

The 2026 Guide to Eating Ontario Fish carries consumption advice for seven species taken from Thunder Lake, tested for contaminants at a sampling location in Zealand Twp., Kenora 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. Where the guide has no result yet for certain contaminants at a location, it sets a precautionary limit of 16 meals a month. 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 5

Thunder Lake lies in Fisheries Management Zone 5. Ontario sets its fishing seasons and catch limits by zone.

Fisheries management zones around Thunder Lake

Zone-wide, Smelt may not be used as bait or possessed for use as bait.

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

Islands and names

Thunder Lake contains eleven islands in the Ontario Hydro Network’s outline, zero of them over 10 hectares and seven under a tenth of a hectare.

Official names

Ontario’s geographic names register lists 2 official names on the water and its islands: two bays. A further 2 named points stand on the mainland shore.

Bays 2

• Hoffstrom's Bay
• Rutter's Bay

Points on the shore 2

• McKay's Point
• Skillen's Point

Nearby lakes

• Wabigoon Lake8 km away
• Dinorwic Lake19 km away
• Eagle Lake40 km away
• Minnitaki Lake57 km away

All lakes

Questions about Thunder Lake

• How deep is Thunder Lake?

  Its deepest charted contour is 21.3 meters, and the water within it is deeper.

• How big is Thunder Lake?

  Its surface covers 11.3 square kilometers and it holds 11 islands. Of its 24 kilometers of shoreline, 22 kilometers is the mainland shore and 2 kilometers is the shore of the islands.

• What fish are in Thunder Lake?

  Ontario’s aquatic resource records name twenty species, among them lake trout, walleye, smallmouth bass, northern pike, lake whitefish and yellow perch. The lake’s spawning, consumption and stocking records also name brook trout.

• Is the water clear?

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