BC lake · 1.5 ha · Cottonwood River watershed

Unnamed lake in the Cottonwood River watershed

Its median summer total phosphorus over 1992–2001 was 18 µg/L, from 5 readings. Higher than 69% of the 269 BC lakes with at least 5 readings.

The readings

5 summer readings on record from 1992 to 2001, at 1 sampling site.

	Median, latest 10 sampled years	Compared with BC lakes
Total phosphorus	18 µg/L 1992–2001, 5 readings	Higher than 69% of the 269 BC lakes with at least 5 readings.

Total phosphorus the nutrient that most often feeds algae in BC lakes

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 mesotrophic (moderate nutrients and algae).

	Index	Class
From total phosphorus (18 µg/L, 1992–2001)	46	mesotrophic

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

Year	Total phosphorus
2001	18 µg/L (1)
2000	20 µg/L (3)
1992	14 µg/L (1)

Median of each year's May to October readings; the number of readings is in brackets.

Where it was sampled

0803024 MILBURN LAKE SOUTH END EAST BAY 6 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.