PlaceDossier / BC places / Lakes

BC lake · 18 km² · Shuswap Lake watershed

Mara Lake

Its median summer Secchi depth over 2012–2025 was 7.6 m, from 71 readings. Clearer than 80% of the 62 BC lakes with enough recent readings.

The readings

532 summer readings from open water on record from 1971 to 2025, at 4 sampling sites.

Median since 2012Compared with BC lakes
Secchi depth7.6 m
2012–2025, 71 readings		Clearer than 80% of the 62 BC lakes with enough recent readings.
Total phosphorus4.1 µg/L
2012–2025, 71 readings		Lower than 80% of the 100 BC lakes with enough recent readings (lower is clearer).
Chlorophyll a1.7 µg/L
2012–2025, 71 readings		Lower than 56% of the 83 BC lakes with enough recent readings (lower is clearer).
Secchi depth how deep a black-and-white disc stays visible: deeper means clearer water
0510 19801990200020102020 1971: median 2.4 m from 1 reading1973: median 9.5 m from 1 reading1974: median 6.1 m from 1 reading1975: median 2.7 m from 4 readings1976: median 1.8 m from 4 readings1977: median 6.8 m from 2 readings1978: median 5.5 m from 3 readings1979: median 7.5 m from 2 readings1980: median 8.2 m from 2 readings1981: median 6.5 m from 2 readings1982: median 7.1 m from 2 readings1983: median 8.3 m from 2 readings1984: median 9.6 m from 2 readings1985: median 9.8 m from 2 readings1987: median 10.1 m from 1 reading1988: median 9.3 m from 2 readings1990: median 10.5 m from 1 reading1991: median 11.8 m from 1 reading1992: median 9.3 m from 2 readings1994: median 7.9 m from 2 readings1995: median 8.3 m from 2 readings1998: median 7.5 m from 2 readings1999: median 9.1 m from 1 reading2000: median 7.7 m from 2 readings2001: median 7.3 m from 2 readings2002: median 6.3 m from 1 reading2003: median 8.8 m from 2 readings2004: median 9.1 m from 2 readings2009: median 7.8 m from 8 readings2010: median 8.0 m from 7 readings2011: median 3.1 m from 21 readings2012: median 3.8 m from 13 readings2013: median 4.2 m from 13 readings2014: median 7.5 m from 9 readings2015: median 6.9 m from 8 readings2016: median 10.3 m from 3 readings2017: median 10.3 m from 2 readings2018: median 11 m from 2 readings2019: median 7.8 m from 9 readings2020: median 10.8 m from 2 readings2021: median 10.3 m from 2 readings2022: median 12.1 m from 2 readings2023: median 10.0 m from 2 readings2024: median 11.2 m from 2 readings2025: median 11.2 m from 2 readingsm
Total phosphorus the nutrient that most often feeds algae in BC lakes
31030 19801990200020102020 1971: median 12 µg/L from 6 readings1974: median 5.0 µg/L from 1 reading1975: median 9.0 µg/L from 4 readings1976: median 10 µg/L from 4 readings1977: median 7.5 µg/L from 2 readings1978: median 6.0 µg/L from 3 readings1979: median 7.5 µg/L from 2 readings1980: median 7.5 µg/L from 2 readings1981: median 8.0 µg/L from 2 readings1982: median 8.5 µg/L from 2 readings1983: median 10 µg/L from 2 readings1984: median 72 µg/L from 2 readings1985: median 7.5 µg/L from 2 readings1986: median 5.0 µg/L from 2 readings1987: median 8.0 µg/L from 2 readings1988: median 3.5 µg/L from 2 readings1989: median 3.5 µg/L from 2 readings1990: median 5.0 µg/L from 2 readings1991: median 4.5 µg/L from 2 readings1992: median 4.5 µg/L from 2 readings1993: median 4.0 µg/L from 2 readings1994: median 5.0 µg/L from 3 readings1995: median 5.0 µg/L from 2 readings1996: median 4.5 µg/L from 2 readings1998: median 6.0 µg/L from 3 readings1999: median 9.5 µg/L from 2 readings2000: median 9.5 µg/L from 2 readings2001: median 3.0 µg/L from 2 readings2002: median 4.0 µg/L from 1 reading2003: median 2.0 µg/L from 2 readings2004: median 5.5 µg/L from 2 readings2005: median 2.5 µg/L from 2 readings2006: median 2.0 µg/L from 2 readings2007: median 4.5 µg/L from 2 readings2008: median 4.0 µg/L from 7 readings2009: median 4.0 µg/L from 8 readings2010: median 5.0 µg/L from 6 readings2011: median 5.0 µg/L from 24 readings2012: median 6.1 µg/L from 13 readings2013: median 5.3 µg/L from 12 readings2014: median 4.0 µg/L from 10 readings2015: median 4.0 µg/L from 8 readings2016: median 8.2 µg/L from 3 readings2017: median 3.0 µg/L from 2 readings2018: median 3.4 µg/L from 2 readings2019: median 3.9 µg/L from 9 readings2020: median 6.9 µg/L from 2 readings2021: median 4.8 µg/L from 2 readings2022: median 6.1 µg/L from 2 readings2023: median 7.2 µg/L from 2 readings2024: median 3.9 µg/L from 2 readings2025: median 3.3 µg/L from 2 readingsµg/L
Chlorophyll a the green pigment in algae: a direct measure of how much is growing
13 19801990200020102020 1975: median 1.5 µg/L from 2 readings1976: median 1.8 µg/L from 4 readings1977: median 1.0 µg/L from 2 readings1978: median 0.9 µg/L from 2 readings1979: median 0.8 µg/L from 2 readings1980: median 1.1 µg/L from 2 readings1981: median 0.9 µg/L from 2 readings1982: median 1.6 µg/L from 2 readings1983: median 1.5 µg/L from 2 readings1984: median 1.2 µg/L from 2 readings1987: median 1.1 µg/L from 2 readings1988: median 1.5 µg/L from 2 readings1989: median 3.2 µg/L from 2 readings1990: median 1.6 µg/L from 2 readings1991: median 1.5 µg/L from 2 readings1992: median 1.8 µg/L from 2 readings1993: median 1.9 µg/L from 2 readings1994: median 1.5 µg/L from 2 readings1995: median 1.8 µg/L from 2 readings1996: median 1.7 µg/L from 2 readings1998: median 1.1 µg/L from 2 readings1999: median 1.6 µg/L from 2 readings2000: median 2.3 µg/L from 2 readings2001: median 4.3 µg/L from 2 readings2002: median 0.5 µg/L from 1 reading2003: median 0.5 µg/L from 2 readings2004: median 1.9 µg/L from 2 readings2005: median 1.2 µg/L from 2 readings2006: median 0.9 µg/L from 2 readings2007: median 1.4 µg/L from 2 readings2008: median 1.2 µg/L from 6 readings2009: median 1.4 µg/L from 8 readings2010: median 1.5 µg/L from 9 readings2011: median 2.9 µg/L from 24 readings2012: median 2.4 µg/L from 13 readings2013: median 2.2 µg/L from 12 readings2014: median 2.1 µg/L from 10 readings2015: median 1.2 µg/L from 8 readings2016: median 0.5 µg/L from 3 readings2017: median 1.1 µg/L from 2 readings2018: median 0.5 µg/L from 2 readings2019: median 1.4 µg/L from 9 readings2020: median 1.3 µg/L from 2 readings2021: median 1.7 µg/L from 2 readings2022: median 0.5 µg/L from 2 readings2023: median 1.3 µg/L from 2 readings2024: median 0.6 µg/L from 2 readings2025: median 0.7 µg/L from 2 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

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

IndexClass
From secchi depth (7.6 m, 2012–2025)31oligotrophic
From total phosphorus (4.1 µg/L, 2012–2025)24oligotrophic
From chlorophyll a (1.7 µg/L, 2012–2025)36oligotrophic

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

YearSecchi depthTotal phosphorusChlorophyll a
202511.2 m (2)3.3 µg/L (2)0.7 µg/L (2)
202411.2 m (2)3.9 µg/L (2)0.6 µg/L (2)
202310.0 m (2)7.2 µg/L (2)1.3 µg/L (2)
202212.1 m (2)6.1 µg/L (2)0.5 µg/L (2)
202110.3 m (2)4.8 µg/L (2)1.7 µg/L (2)
202010.8 m (2)6.9 µg/L (2)1.3 µg/L (2)
20197.8 m (9)3.9 µg/L (9)1.4 µg/L (9)
201811 m (2)3.4 µg/L (2)0.5 µg/L (2)
201710.3 m (2)3.0 µg/L (2)1.1 µg/L (2)
201610.3 m (3)8.2 µg/L (3)0.5 µg/L (3)
20156.9 m (8)4.0 µg/L (8)1.2 µg/L (8)
20147.5 m (9)4.0 µg/L (10)2.1 µg/L (10)
20134.2 m (13)5.3 µg/L (12)2.2 µg/L (12)
20123.8 m (13)6.1 µg/L (13)2.4 µg/L (13)
20113.1 m (21)5.0 µg/L (24)2.9 µg/L (24)
20108.0 m (7)5.0 µg/L (6)1.5 µg/L (9)
20097.8 m (8)4.0 µg/L (8)1.4 µg/L (8)
2008–4.0 µg/L (7)1.2 µg/L (6)
2007–4.5 µg/L (2)1.4 µg/L (2)
2006–2.0 µg/L (2)0.9 µg/L (2)
2005–2.5 µg/L (2)1.2 µg/L (2)
20049.1 m (2)5.5 µg/L (2)1.9 µg/L (2)
20038.8 m (2)2.0 µg/L (2)0.5 µg/L (2)
20026.3 m (1)4.0 µg/L (1)0.5 µg/L (1)
20017.3 m (2)3.0 µg/L (2)4.3 µg/L (2)
20007.7 m (2)9.5 µg/L (2)2.3 µg/L (2)
19999.1 m (1)9.5 µg/L (2)1.6 µg/L (2)
19987.5 m (2)6.0 µg/L (3)1.1 µg/L (2)
1996–4.5 µg/L (2)1.7 µg/L (2)
19958.3 m (2)5.0 µg/L (2)1.8 µg/L (2)
19947.9 m (2)5.0 µg/L (3)1.5 µg/L (2)
1993–4.0 µg/L (2)1.9 µg/L (2)
19929.3 m (2)4.5 µg/L (2)1.8 µg/L (2)
199111.8 m (1)4.5 µg/L (2)1.5 µg/L (2)
199010.5 m (1)5.0 µg/L (2)1.6 µg/L (2)
1989–3.5 µg/L (2)3.2 µg/L (2)
19889.3 m (2)3.5 µg/L (2)1.5 µg/L (2)
198710.1 m (1)8.0 µg/L (2)1.1 µg/L (2)
1986–5.0 µg/L (2)–
19859.8 m (2)7.5 µg/L (2)–
19849.6 m (2)72 µg/L (2)1.2 µg/L (2)
19838.3 m (2)10 µg/L (2)1.5 µg/L (2)
19827.1 m (2)8.5 µg/L (2)1.6 µg/L (2)
19816.5 m (2)8.0 µg/L (2)0.9 µg/L (2)
19808.2 m (2)7.5 µg/L (2)1.1 µg/L (2)
19797.5 m (2)7.5 µg/L (2)0.8 µg/L (2)
19785.5 m (3)6.0 µg/L (3)0.9 µg/L (2)
19776.8 m (2)7.5 µg/L (2)1.0 µg/L (2)
19761.8 m (4)10 µg/L (4)1.8 µg/L (4)
19752.7 m (4)9.0 µg/L (4)1.5 µg/L (2)
19746.1 m (1)5.0 µg/L (1)–
19739.5 m (1)––
19712.4 m (1)12 µg/L (6)–

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

  • 0500128 Opposite Fossett 359 readings
  • 0500451 East mouth Shuswap River 111 readings
  • E285689 Mara south off Kingbaker C 61 readings
  • E233525 Off Swansea Point 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 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.