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Map of Lac William with depth contours

Lac William

46.1161° N, 71.5678° W

Depth contours from the 2012 government survey. Not for navigation.

Download the depth map (SVG)

Lac William, Quebec. 46.1161° N, 71.5678° W

Maximum depth 30.2 m (2012 survey). Scale bar on the map.

Not for navigation. Depths are from government surveys and may be outdated.

borealbound.ca/lakes/qc/lac-william/, compiled October 9, 2026

  • Canadian Geographical Names Database, Natural Resources Canada. Contains information licensed under the Open Government Licence – Canada.
  • HydroLAKES v1.0, Messager et al. 2016 / WWF HydroSHEDS. Licensed under CC BY 4.0.
  • Census boundaries and population, 2021, Statistics Canada. Adapted from Statistics Canada. This does not constitute an endorsement by Statistics Canada.
  • Géobase des bathymétries de lac du Québec (GBLQ), Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs. Licensed under CC BY 4.0. Source: Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (MELCCFP), Données Québec.
  • États trophiques des lacs (RSVL), Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs. Licensed under CC BY 4.0. Source: Ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (MELCCFP), Données Québec.
  • City page weather forecasts and alerts, Environment and Climate Change Canada. Contains data from Environment and Climate Change Canada (ECCC Data Servers End-use Licence).
  • Photographs, Wikimedia Commons contributors. Each photo carries its own licence (CC0, public domain, CC BY or CC BY-SA), credited where shown.

Lac William is 30.2 m deep at its deepest point, deeper than 81% of the 1,506 surveyed lakes in Quebec. It covers 4.9 km² and lies beside Lac-William.

Maximum depth
30.2 msurveyed 2012
deeper than 81% of the 1,506 surveyed lakes in Quebec
Area
4.9 km²
larger than 91% of the 29,407 lakes in Quebec
Shoreline
19.1 km
longer than 87% of the 29,407 lakes in Quebec
Water clarity
1.4 mSecchi depth, 2025
less clear than 95% of the 805 monitored lakes in Quebec
Elevation
195 m

Today on the water

4.8 °C

Wind SW 9 km/h

Observed at Thetford Mines, as of 3:00 a.m. EDT

choppy Estimated waves, next 12 hours: up to 0.2 m. Around 9 a.m., wind from the west: the west shore is sheltered, waves build toward the east shore.

Time4 a.m.7 a.m.10 a.m.1 p.m.4 p.m.7 p.m.10 p.m.1 a.m.
Wind km/hW 10W 10W 20W 20W 20W 20W 15W 10
Gusts km/h404040
Waves (est.) m0.10.10.20.2
Temp. °C9891110753
Precip. %60404040404000

Tonight: Mainly cloudy with 60 percent chance of showers. Risk of a thunderstorm this evening. Wind west 20 km/h gusting to 40 becoming light this evening. Low 8.

Weather: Thetford Mines (local forecast), as of 3:02 a.m. EDT

Sun and moon

Civil dawn
6:25 a.m.
Sunrise
6:55 a.m.
Sunset
6:10 p.m.
Civil dusk
6:40 p.m.
Moonrise
5:45 a.m.
Moonset
5:29 p.m.
Moon
Waning crescent, 1% lit

Data Source: Environment and Climate Change Canada. Local times.

How waves are estimated

Significant wave height from the forecast hourly wind and the open-water distance (fetch) upwind, using the SMB method (US Army Corps of Engineers Shore Protection Manual, 1984), rounded up to the next 0.1 m. It is not a measurement: gusts, leftover swell and shoals can make water rougher. Under 0.2 m: calm; 0.2–0.5 m: choppy; over 0.5 m: rough.

Depth

17% of Lac William is shallower than 3 m, and 47% is deeper than 10 m.

How to read it: the lake’s area is sorted from the shore to the deepest point. Where the curve is flat, large areas share one depth (flats and weed beds); where it drops, depth changes quickly (drop-offs).

The government depth survey from 2012 records a maximum depth of 30.2 m, drawn from 53 depth contours.

Not for navigation. Depths are from government surveys and may be outdated.

Water

Trophic status from the latest monitoring: eutrophic.

Clarity was measured with a Secchi disk in 12 years between 2010 and 2025; the latest annual mean is 1.4 m.

Water clarity (Secchi depth, m)
Total phosphorus (µg/L)

Photos

Manoir du lac William (2)
Photo: Gabriel Picard, CC BY-SA 4.0, via Wikimedia Commons
Manoir du lac William (1)
Photo: Gabriel Picard, CC BY-SA 4.0, via Wikimedia Commons