Why rank lakes by phosphorus?

Phosphorus is usually what limits how much algae a lake can grow, so it is the earliest signal that a lake is under nutrient pressure. It is also the measurement these agencies publish most consistently, which makes it the fairest way to compare lakes across a country.

Is a low-phosphorus lake safe to swim in?

Not necessarily. A lightly loaded lake can still carry bacteria, a seasonal algal bloom, or contaminants that a nutrient reading does not cover. Check the local authority notice for the day you plan to go.

What is a typical phosphorus level in England?

The median measured lake in England reads 52 µg/L of total phosphorus. Lakes below roughly 10 µg/L are considered nutrient-poor and usually run clear; above about 30 µg/L a lake is generally nutrient-rich and more likely to green up in summer.

Cleanest lakes in England

Cleanest lakes in England: 524 named lakes have an official total-phosphorus reading. The 20 below carry the lowest nutrient load — a measurement, not a LakeQuality A–F grade.

Lake map

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Lowest phosphorus readings in England

Phosphorus is the nutrient that feeds algae growth, so the lakes at the top of this table are the least loaded ones the England monitoring programme has measured. The median measured lake in England reads 52 µg/L.

Lake	Place	Total phosphorus	Chlorophyll-a	Secchi	Year
Wast Water	Cumbria and Lancashire	2.6 µg/L	1.2 µg/L	—	2026
Blea Water	Cumbria and Lancashire	2.8 µg/L	1.0 µg/L	—	2022
Ennerdale Water	Cumbria and Lancashire	3.1 µg/L	1.5 µg/L	—	2026
Devoke Water	Cumbria and Lancashire	4.1 µg/L	2.3 µg/L	—	2026
Buttermere	Cumbria and Lancashire	4.4 µg/L	1.8 µg/L	—	2026
Little Langdale Tarn	Cumbria and Lancashire	4.4 µg/L	2.2 µg/L	—	2026
Brotherswater	Cumbria and Lancashire	5.3 µg/L	1.5 µg/L	—	2026
Buttermere As Part of A Wq Survey	Cumbria and Lancashire	6.5 µg/L	3.1 µg/L	—	2026
Tarn Hows	Cumbria and Lancashire	6.5 µg/L	2.8 µg/L	—	2026
Coniston Lake	Cumbria and Lancashire	6.8 µg/L	2.7 µg/L	—	2026
Hawes Water	Cumbria and Lancashire	7.5 µg/L	3.5 µg/L	—	2026
Derwentwater	Cumbria and Lancashire	7.9 µg/L	3.5 µg/L	—	2026
Churn Clough Reservoir	Cumbria and Lancashire	8.5 µg/L	2.3 µg/L	—	2020
Ullswater	Cumbria and Lancashire	9.1 µg/L	2.6 µg/L	—	2026
Cow Green Reservoir	Northumberland Durham and Tees	9.2 µg/L	1.0 µg/L	—	2020
River Avon Lake	Devon and Cornwall	9.6 µg/L	1.7 µg/L	—	2020
Fernworthy Reservoir Surface	Devon and Cornwall	10 µg/L	5.2 µg/L	—	2023
Rydal Water Shore	Cumbria and Lancashire	10 µg/L	3.4 µg/L	—	2026
Yateholme Reservoir	Yorkshire	10 µg/L	2.9 µg/L	—	2025
Walkerwood Reservoir	Gtr Mancs Mersey and Ches	11 µg/L	3.2 µg/L	—	2020

Showing 20 of 524 named lakes. Open a county or place page for the rest.

Frequently asked questions

Which lakes in England are the cleanest?: 524 named lakes in England have an official total-phosphorus reading. This page ranks the 20 lowest. Phosphorus is the nutrient that feeds algae growth, so a low reading means a lightly loaded lake — it is not a swim-safety class and not a LakeQuality A–F grade.
Why rank lakes by phosphorus?: Phosphorus is usually what limits how much algae a lake can grow, so it is the earliest signal that a lake is under nutrient pressure. It is also the measurement these agencies publish most consistently, which makes it the fairest way to compare lakes across a country.
Is a low-phosphorus lake safe to swim in?: Not necessarily. A lightly loaded lake can still carry bacteria, a seasonal algal bloom, or contaminants that a nutrient reading does not cover. Check the local authority notice for the day you plan to go.
What is a typical phosphorus level in England?: The median measured lake in England reads 52 µg/L of total phosphorus. Lakes below roughly 10 µg/L are considered nutrient-poor and usually run clear; above about 30 µg/L a lake is generally nutrient-rich and more likely to green up in summer.