PlaceDossier / BC places / Lakes

BC lake · 1 km² · Cowichan watershed

Quennell Lake

Too few readings to judge this lake: 166 summer readings from open water between 1985 and 2024, and we need at least 10 summer readings from open water, spread over at least 3 different years, since 2012 before we summarise or compare it. The readings are below.

The readings

166 summer readings from open water on record from 1985 to 2024, at 4 sampling sites.

Median since 2012Compared with BC lakes
Secchi depthToo few readings to judge
31 readings since 2012, in 2 years		Too few readings to compare (31 readings since 2012, in 2 years).
Total phosphorusToo few readings to judge
52 readings since 2012, in 2 years		Too few readings to compare (52 readings since 2012, in 2 years).
Chlorophyll aToo few readings to judge
31 readings since 2012, in 2 years		Too few readings to compare (31 readings since 2012, in 2 years).
Secchi depth how deep a black-and-white disc stays visible: deeper means clearer water
0246 1990200020102020 2002: median 2.3 m from 1 reading2003: median 2.4 m from 1 reading2004: median 1.5 m from 2 readings2023: median 1.3 m from 11 readings2024: median 1.1 m from 20 readingsm
Total phosphorus the nutrient that most often feeds algae in BC lakes
1030100 1990200020102020 1985: median 76 µg/L from 3 readings1992: median 114 µg/L from 2 readings2001: median 100 µg/L from 8 readings2002: median 96 µg/L from 12 readings2003: median 51 µg/L from 12 readings2004: median 61 µg/L from 4 readings2023: median 59 µg/L from 22 readings2024: median 64 µg/L from 30 readingsµg/L
Chlorophyll a the green pigment in algae: a direct measure of how much is growing
131030 1990200020102020 2002: median 16 µg/L from 5 readings2003: median 3.7 µg/L from 2 readings2023: median 23 µg/L from 11 readings2024: median 25 µg/L from 20 readingsµg/L

Median each year (bigger dot, more readings)Middle half of BC lakesBC median

Source: BC Environmental Monitoring Data System (EnMoDS) results, Environmental Monitoring and Analysis Branch, Province of BC, records to September 19, 2026 (Open Government Licence – British Columbia); lake outlines and names: Freshwater Atlas lakes, Province of BC (Open Government Licence – British Columbia). Summaries by PlaceDossier.

Nutrient level Inferred

Unclear: too few readings to judge this lake's nutrient level.

Left out for too few recent readings (we need at least 10 summer readings from open water, spread over at least 3 different years, since 2012): secchi depth (31 readings since 2012, in 2 years); total phosphorus (52 readings since 2012, in 2 years); chlorophyll a (31 readings since 2012, in 2 years).

Year by year

YearSecchi depthTotal phosphorusChlorophyll a
20241.1 m (20)64 µg/L (30)25 µg/L (20)
20231.3 m (11)59 µg/L (22)23 µg/L (11)
20041.5 m (2)61 µg/L (4)–
20032.4 m (1)51 µg/L (12)3.7 µg/L (2)
20022.3 m (1)96 µg/L (12)16 µg/L (5)
2001–100 µg/L (8)–
1992–114 µg/L (2)–
1985–76 µg/L (3)–

Median of each year's May to October readings; the number of readings is in brackets.

Source: BC Environmental Monitoring Data System (EnMoDS) results, Environmental Monitoring and Analysis Branch, Province of BC, records to September 19, 2026 (Open Government Licence – British Columbia); lake outlines and names: Freshwater Atlas lakes, Province of BC (Open Government Licence – British Columbia). Summaries by PlaceDossier.

Where it was sampled

  • E330872 Deepest point (east narrows centre) 74 readings
  • E330873 West basin 40 readings
  • 1100142 West end 29 readings
  • 1100141 East end 23 readings

Site names are tidied from the provincial records; the IDs find each site's full record there.

What this record doesn't cover

Algae bloom reports and invasive mussel checks aren't in this record: the province's Algae Watch map and mussel monitoring aren't published as open data. For swimming, check the regional health authority's beach advisories; for blooms and mussels, ask the province's regional environment office or the local lake association.

Readings are from the province's monitoring database: samples taken by provincial staff, volunteer lake monitors, and companies and local governments that sample under their permits. We keep the ice-free season (May to October), and for phosphorus and chlorophyll only samples from the top 5 m. We leave out sites whose names put them at a water intake, a sewage or industrial outfall, a mine or a permit holder's works, or on the shore (a beach, dock or boat launch): water there can differ a lot from the open lake. Each year's figure is the median of that year's readings. We give a lake a summary, a comparison with other lakes and a nutrient level only when it has at least 10 summer readings from open water, spread over at least 3 different years, since 2012; the summary is the median of those readings. With fewer, or only older ones, we show the readings and say there are too few to judge the lake. A reading below the lab's detection limit counts at that limit. One site can be a bay rather than the open lake, so a lake's figures can differ from one end to the other.

Water quality changes with the season, the weather and the part of the lake. These are past readings, not a test of the water today: before you buy, ask the local government and the lake association what's known, and test a drinking-water intake yourself.