PlaceDossier / BC places / Lakes

BC lake · 5 km² · Quesnel River watershed

Dragon Lake

Its median summer Secchi depth over 2016–2025 was 5.0 m, from 14 readings. Clearer than 50% of the 122 BC lakes with at least 5 readings.

The readings

240 summer readings on record from 1973 to 2025, at 5 sampling sites.

Median, latest 10 sampled yearsCompared with BC lakes
Secchi depth5.0 m
2016–2025, 14 readings		Clearer than 50% of the 122 BC lakes with at least 5 readings.
Total phosphorus8.8 µg/L
2016–2025, 15 readings		Lower than 60% of the 269 BC lakes with at least 5 readings (lower is clearer).
Chlorophyll a1.4 µg/L
2016–2025, 14 readings		Lower than 63% of the 156 BC lakes with at least 5 readings (lower is clearer).
Secchi depth how deep a black-and-white disc stays visible: deeper means clearer water
0246 19801990200020102020 1980: median 5.8 m from 5 readings1982: median 3.8 m from 2 readings1983: median 2.5 m from 4 readings1984: median 6.5 m from 9 readings2016: median 4.1 m from 1 reading2017: median 5.3 m from 1 reading2018: median 5.7 m from 2 readings2019: median 4.3 m from 2 readings2020: median 4.9 m from 1 reading2021: median 5.8 m from 2 readings2022: median 6.7 m from 1 reading2023: median 5.3 m from 2 readings2024: median 4.9 m from 1 reading2025: median 4.8 m from 1 readingm
Total phosphorus the nutrient that most often feeds algae in BC lakes
1030100300 19801990200020102020 1973: median 8.0 µg/L from 1 reading1974: median 9.0 µg/L from 3 readings1980: median 29 µg/L from 12 readings1982: median 23 µg/L from 2 readings1983: median 68 µg/L from 6 readings1984: median 23 µg/L from 18 readings1985: median 18 µg/L from 28 readings1986: median 18 µg/L from 2 readings1987: median 42 µg/L from 4 readings1988: median 28 µg/L from 16 readings1990: median 99 µg/L from 1 reading1995: median 20 µg/L from 1 reading2004: median 488 µg/L from 2 readings2006: median 56 µg/L from 2 readings2007: median 21 µg/L from 12 readings2008: median 22 µg/L from 8 readings2009: median 10 µg/L from 11 readings2011: median 9.0 µg/L from 1 reading2014: median 15 µg/L from 1 reading2015: median 7.1 µg/L from 4 readings2016: median 11 µg/L from 1 reading2017: median 8.8 µg/L from 1 reading2018: median 10 µg/L from 2 readings2019: median 7.4 µg/L from 2 readings2020: median 7.8 µg/L from 2 readings2021: median 6.8 µg/L from 2 readings2022: median 7.0 µg/L from 1 reading2023: median 7.9 µg/L from 2 readings2024: median 10 µg/L from 1 reading2025: median 4.6 µg/L from 1 readingµg/L
Chlorophyll a the green pigment in algae: a direct measure of how much is growing
131030 19801990200020102020 1980: median 1.6 µg/L from 4 readings1983: median 27 µg/L from 4 readings1984: median 1.1 µg/L from 15 readings1985: median 1.1 µg/L from 6 readings2007: median 3.7 µg/L from 4 readings2008: median 4.2 µg/L from 4 readings2009: median 4.6 µg/L from 4 readings2015: median 3.6 µg/L from 1 reading2016: median 2.5 µg/L from 1 reading2017: median 1.5 µg/L from 1 reading2018: median 0.6 µg/L from 2 readings2019: median 2.2 µg/L from 2 readings2020: median 1.8 µg/L from 1 reading2021: median 1.4 µg/L from 2 readings2022: median 1.1 µg/L from 1 reading2023: median 1.1 µg/L from 2 readings2024: median 1.3 µg/L from 1 reading2025: median 1.5 µg/L from 1 readingµg/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

Reads as oligotrophic (few nutrients, little algae, usually clear).

IndexClass
From secchi depth (5.0 m, 2016–2025)37oligotrophic
From total phosphorus (8.8 µg/L, 2016–2025)36oligotrophic
From chlorophyll a (1.4 µg/L, 2016–2025)34oligotrophic

Inferred by us, not a provincial classification. Carlson's trophic state index (Carlson 1977, Limnology and Oceanography 22:361) turns each median into a score: 60 − 14.41 ln(Secchi m), 14.42 ln(phosphorus µg/L) + 4.15, 9.81 ln(chlorophyll µg/L) + 30.6. Classes after Carlson and Simpson (1996): under 40 oligotrophic, 40 to 50 mesotrophic, 50 to 70 eutrophic, 70 and over hypereutrophic. The index was built for summer readings from the middle of a lake; ours mix sites and months, so treat the class as a rough guide.

Year by year

YearSecchi depthTotal phosphorusChlorophyll a
20254.8 m (1)4.6 µg/L (1)1.5 µg/L (1)
20244.9 m (1)10 µg/L (1)1.3 µg/L (1)
20235.3 m (2)7.9 µg/L (2)1.1 µg/L (2)
20226.7 m (1)7.0 µg/L (1)1.1 µg/L (1)
20215.8 m (2)6.8 µg/L (2)1.4 µg/L (2)
20204.9 m (1)7.8 µg/L (2)1.8 µg/L (1)
20194.3 m (2)7.4 µg/L (2)2.2 µg/L (2)
20185.7 m (2)10 µg/L (2)0.6 µg/L (2)
20175.3 m (1)8.8 µg/L (1)1.5 µg/L (1)
20164.1 m (1)11 µg/L (1)2.5 µg/L (1)
2015–7.1 µg/L (4)3.6 µg/L (1)
2014–15 µg/L (1)–
2011–9.0 µg/L (1)–
2009–10 µg/L (11)4.6 µg/L (4)
2008–22 µg/L (8)4.2 µg/L (4)
2007–21 µg/L (12)3.7 µg/L (4)
2006–56 µg/L (2)–
2004–488 µg/L (2)–
1995–20 µg/L (1)–
1990–99 µg/L (1)–
1988–28 µg/L (16)–
1987–42 µg/L (4)–
1986–18 µg/L (2)–
1985–18 µg/L (28)1.1 µg/L (6)
19846.5 m (9)23 µg/L (18)1.1 µg/L (15)
19832.5 m (4)68 µg/L (6)27 µg/L (4)
19823.8 m (2)23 µg/L (2)–
19805.8 m (5)29 µg/L (12)1.6 µg/L (4)
1974–9.0 µg/L (3)–
1973–8.0 µg/L (1)–

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

  • 0603017 DRAGON LK. AT MIDDLE 209 readings
  • 0803011 DRAGON LAKE AT SOUTH POINT 42 readings
  • 0603016 DRAGON LK. AT SOUTH END 19 readings
  • 0603018 DRAGON LK. AT NORTH END 18 readings
  • E252117 DRAGON LAKE 8 readings

Site names and IDs are as recorded in the provincial database; 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. Each year's figure is the median of that year's readings; the summary is the median of every reading in the lake's latest 10 sampled years. 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.