PlaceDossier / BC places / Lakes

BC lake · 5 km² · Lower Chilako River watershed

Nadsilnich Lake

Its median summer Secchi depth over 2017–2025 was 1.5 m, from 15 readings. Murkier than 93% of the 122 BC lakes with at least 5 readings.

The readings

215 summer readings on record from 1983 to 2026, at 3 sampling sites.

Median, latest 10 sampled yearsCompared with BC lakes
Secchi depth1.5 m
2017–2025, 15 readings		Murkier than 93% of the 122 BC lakes with at least 5 readings.
Total phosphorus27 µg/L
2017–2026, 19 readings		Higher than 78% of the 269 BC lakes with at least 5 readings.
Chlorophyll a14 µg/L
2017–2026, 15 readings		Higher than 93% of the 156 BC lakes with at least 5 readings.
Secchi depth how deep a black-and-white disc stays visible: deeper means clearer water
0246 1990200020102020 2017: median 1.9 m from 2 readings2018: median 1.0 m from 2 readings2019: median 1.6 m from 2 readings2020: median 1.7 m from 1 reading2021: median 1.6 m from 2 readings2022: median 1.9 m from 2 readings2023: median 1.4 m from 2 readings2024: median 2.2 m from 1 reading2025: median 2.4 m from 1 readingm
Total phosphorus the nutrient that most often feeds algae in BC lakes
1030 1990200020102020 1983: median 16 µg/L from 1 reading1985: median 41 µg/L from 2 readings1986: median 28 µg/L from 1 reading1987: median 43 µg/L from 3 readings1988: median 15 µg/L from 1 reading1989: median 25 µg/L from 2 readings1990: median 18 µg/L from 21 readings1991: median 18 µg/L from 15 readings1992: median 17 µg/L from 1 reading1994: median 20 µg/L from 6 readings1995: median 18 µg/L from 13 readings1996: median 15 µg/L from 3 readings1997: median 30 µg/L from 4 readings2002: median 15 µg/L from 9 readings2005: median 10 µg/L from 1 reading2013: median 23 µg/L from 4 readings2014: median 22 µg/L from 12 readings2015: median 20 µg/L from 12 readings2016: median 29 µg/L from 13 readings2017: median 40 µg/L from 2 readings2018: median 36 µg/L from 2 readings2019: median 37 µg/L from 2 readings2020: median 22 µg/L from 1 reading2021: median 48 µg/L from 4 readings2022: median 28 µg/L from 2 readings2023: median 36 µg/L from 2 readings2024: median 17 µg/L from 1 reading2025: median 19 µg/L from 1 reading2026: median 55 µg/L from 2 readingsµg/L
Chlorophyll a the green pigment in algae: a direct measure of how much is growing
1310 1990200020102020 1983: median 3.7 µg/L from 1 reading1985: median 8.0 µg/L from 1 reading2002: median 4.8 µg/L from 9 readings2013: median 6.2 µg/L from 6 readings2014: median 7.5 µg/L from 3 readings2015: median 7.6 µg/L from 13 readings2016: median 23 µg/L from 9 readings2017: median 20 µg/L from 2 readings2018: median 15 µg/L from 2 readings2019: median 12 µg/L from 2 readings2020: median 19 µg/L from 1 reading2021: median 18 µg/L from 1 reading2022: median 11 µg/L from 2 readings2023: median 11 µg/L from 2 readings2024: median 8.5 µg/L from 1 reading2025: median 7.0 µg/L from 1 reading2026: median 4.3 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 eutrophic (rich in nutrients, with more algae and weed growth).

IndexClass
From secchi depth (1.5 m, 2017–2025)54eutrophic
From total phosphorus (27 µg/L, 2017–2026)51eutrophic
From chlorophyll a (14 µg/L, 2017–2026)56eutrophic

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
2026–55 µg/L (2)4.3 µg/L (1)
20252.4 m (1)19 µg/L (1)7.0 µg/L (1)
20242.2 m (1)17 µg/L (1)8.5 µg/L (1)
20231.4 m (2)36 µg/L (2)11 µg/L (2)
20221.9 m (2)28 µg/L (2)11 µg/L (2)
20211.6 m (2)48 µg/L (4)18 µg/L (1)
20201.7 m (1)22 µg/L (1)19 µg/L (1)
20191.6 m (2)37 µg/L (2)12 µg/L (2)
20181.0 m (2)36 µg/L (2)15 µg/L (2)
20171.9 m (2)40 µg/L (2)20 µg/L (2)
2016–29 µg/L (13)23 µg/L (9)
2015–20 µg/L (12)7.6 µg/L (13)
2014–22 µg/L (12)7.5 µg/L (3)
2013–23 µg/L (4)6.2 µg/L (6)
2005–10 µg/L (1)–
2002–15 µg/L (9)4.8 µg/L (9)
1997–30 µg/L (4)–
1996–15 µg/L (3)–
1995–18 µg/L (13)–
1994–20 µg/L (6)–
1992–17 µg/L (1)–
1991–18 µg/L (15)–
1990–18 µg/L (21)–
1989–25 µg/L (2)–
1988–15 µg/L (1)–
1987–43 µg/L (3)–
1986–28 µg/L (1)–
1985–41 µg/L (2)8.0 µg/L (1)
1983–16 µg/L (1)3.7 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

  • 0400489 NADSILNICH (WEST) L DEEP STN CENTER N. END 214 readings
  • E209113 WEST (NADSILNICH) LAKE SOUTH STATION 28 readings
  • E227193 WEST (NADSILNICH) LAKE LITTORAL SITE 1 reading

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.