PlaceDossier / BC places / Lakes
BC lake · 6 km² · Lower Peace River watershed
Swan Lake
Its median summer Secchi depth over 2016–2025 was 1.3 m, from 16 readings. Murkier than 95% of the 62 BC lakes with enough recent readings.
The readings
140 summer readings from open water on record from 1979 to 2025, at 2 sampling sites.
| Median since 2012 | Compared with BC lakes | |
|---|---|---|
| Secchi depth | 1.3 m 2016–2025, 16 readings | Murkier than 95% of the 62 BC lakes with enough recent readings. |
| Total phosphorus | 52 µg/L 2015–2025, 21 readings | Higher than 96% of the 95 BC lakes with enough recent readings. |
| Chlorophyll a | 3.8 µg/L 2015–2025, 18 readings | Higher than 73% of the 83 BC lakes with enough recent readings. |
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
The measures disagree: clarity reads eutrophic, phosphorus reads eutrophic, algae reads mesotrophic. That's common: clarity also depends on silt and colour, not just algae.
| Index | Class | |
|---|---|---|
| From secchi depth (1.3 m, 2016–2025) | 57 | eutrophic |
| From total phosphorus (52 µg/L, 2015–2025) | 61 | eutrophic |
| From chlorophyll a (3.8 µg/L, 2015–2025) | 44 | mesotrophic |
Inferred by us, not a provincial classification. 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.
How we worked this out
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.
Year by year
| Year | Secchi depth | Total phosphorus | Chlorophyll a |
|---|---|---|---|
| 2025 | 2.0 m (1) | 116 µg/L (1) | 3.9 µg/L (1) |
| 2024 | 2.3 m (2) | 36 µg/L (2) | 13 µg/L (2) |
| 2023 | 2.1 m (2) | 41 µg/L (2) | 15 µg/L (2) |
| 2022 | 0.7 m (2) | 71 µg/L (2) | 28 µg/L (2) |
| 2021 | 0.6 m (2) | 72 µg/L (2) | 39 µg/L (2) |
| 2020 | 0.5 m (1) | 90 µg/L (1) | 3.7 µg/L (1) |
| 2019 | 1.4 m (2) | 42 µg/L (2) | 5.0 µg/L (2) |
| 2018 | 1.0 m (1) | 56 µg/L (2) | 2.1 µg/L (1) |
| 2017 | 1.2 m (2) | 64 µg/L (3) | 1.2 µg/L (2) |
| 2016 | 3.3 m (1) | 28 µg/L (2) | 1.0 µg/L (1) |
| 2015 | – | 64 µg/L (2) | 9.8 µg/L (2) |
| 2005 | – | 44 µg/L (26) | – |
| 2004 | – | 83 µg/L (25) | – |
| 2003 | – | 59 µg/L (13) | – |
| 1997 | – | 63 µg/L (2) | – |
| 1989 | – | 43 µg/L (2) | – |
| 1987 | – | 82 µg/L (1) | 5.4 µg/L (1) |
| 1986 | – | 68 µg/L (5) | – |
| 1979 | – | 70 µg/L (6) | 11 µg/L (4) |
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
- 0400935 Centre deep station 7 m depth 139 readings
- E227183 Littoral site 1 reading
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 the water receiving its discharge, 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.