PlaceDossier / BC places / Lakes

BC lake · 12 km² · Chilliwack River watershed

Chilliwack Lake

Its median summer Secchi depth over 2015–2024 was 13 m, from 11 readings. Clearer than 98% of the 122 BC lakes with at least 5 readings.

The readings

35 summer readings on record from 2015 to 2026, at 1 sampling site.

Median, latest 10 sampled yearsCompared with BC lakes
Secchi depth13 m
2015–2024, 11 readings		Clearer than 98% of the 122 BC lakes with at least 5 readings.
Total phosphorus2.0 µg/L
2017–2026, 10 readings		Lower than 97% of the 269 BC lakes with at least 5 readings (lower is clearer).
Chlorophyll a0.5 µg/L
2017–2026, 10 readings		Lower than 94% 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
051015 201520202025 2015: median 9.5 m from 1 reading2016: median 10.3 m from 1 reading2017: median 13 m from 1 reading2018: median 10.5 m from 2 readings2019: median 16.6 m from 1 reading2020: median 14.9 m from 1 reading2021: median 14.6 m from 1 reading2022: median 11.9 m from 1 reading2023: median 12.6 m from 1 reading2024: median 14.9 m from 1 readingm
Total phosphorus the nutrient that most often feeds algae in BC lakes
310 201520202025 2015: median 2.0 µg/L from 1 reading2016: median 3.3 µg/L from 1 reading2017: median 2.0 µg/L from 1 reading2018: median 2.4 µg/L from 2 readings2019: median 2.0 µg/L from 1 reading2020: median 2.0 µg/L from 1 reading2021: median 2.0 µg/L from 1 reading2022: median 2.0 µg/L from 1 reading2023: median 2.3 µg/L from 1 reading2024: median 2.0 µg/L from 1 reading2026: median 2.0 µg/L from 1 readingµg/L
Chlorophyll a the green pigment in algae: a direct measure of how much is growing
0.10.313 201520202025 2015: median 0.4 µg/L from 1 reading2016: median 0.8 µg/L from 1 reading2017: median 0.3 µg/L from 1 reading2018: median 0.7 µg/L from 2 readings2019: median 0.8 µg/L from 1 reading2020: median 0.5 µg/L from 1 reading2021: median 0.6 µg/L from 1 reading2022: median 0.3 µg/L from 1 reading2023: median 0.7 µg/L from 1 reading2024: median 0.1 µg/L from 1 reading2026: median 0.6 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 (13 m, 2015–2024)23oligotrophic
From total phosphorus (2.0 µg/L, 2017–2026)14oligotrophic
From chlorophyll a (0.5 µg/L, 2017–2026)24oligotrophic

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
2026–2.0 µg/L (1)0.6 µg/L (1)
202414.9 m (1)2.0 µg/L (1)0.1 µg/L (1)
202312.6 m (1)2.3 µg/L (1)0.7 µg/L (1)
202211.9 m (1)2.0 µg/L (1)0.3 µg/L (1)
202114.6 m (1)2.0 µg/L (1)0.6 µg/L (1)
202014.9 m (1)2.0 µg/L (1)0.5 µg/L (1)
201916.6 m (1)2.0 µg/L (1)0.8 µg/L (1)
201810.5 m (2)2.4 µg/L (2)0.7 µg/L (2)
201713 m (1)2.0 µg/L (1)0.3 µg/L (1)
201610.3 m (1)3.3 µg/L (1)0.8 µg/L (1)
20159.5 m (1)2.0 µg/L (1)0.4 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

  • E303413 CHILLIWACK LAKE NEAR CENTRE OF THE NORTH 1/2 OF LAKE 56 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.