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 Norway?

The median measured lake in Norway reads 5 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 Norway

Cleanest lakes in Norway: 61 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 Norway

Phosphorus is the nutrient that feeds algae growth, so the lakes at the top of this table are the least loaded ones the Norway monitoring programme has measured. The median measured lake in Norway reads 5 µg/L.

Lake	Place	Total phosphorus	Chlorophyll-a	Secchi	Year
Eikedalsvatnet	—	1.5 µg/L	0.90 µg/L	—	2021
Hornindalsvatnet	—	2.0 µg/L	1.3 µg/L	—	2021
Kapervatnet	—	2.0 µg/L	0.50 µg/L	13 m	2023
Leirbekkvatnet	—	2.0 µg/L	0.70 µg/L	9.5 m	2020
Lille Rostavatn	—	2.0 µg/L	0.60 µg/L	10 m	2020
Steinvatnet	—	2.0 µg/L	0.70 µg/L	15 m	2020
Svartdalsvatnet	—	2.0 µg/L	0.90 µg/L	10 m	2023
Svartetjoerna Lake	—	2.0 µg/L	—	—	2018
Taarnvatnet	—	2.0 µg/L	0.70 µg/L	10 m	2022
Skardvatnet	—	2.3 µg/L	0.90 µg/L	7.3 m	2023
Movatnet Eid	—	2.5 µg/L	0.80 µg/L	9.2 m	2019
Byglandsfjorden Lake	—	3.0 µg/L	1.4 µg/L	—	2021
Femunden Graaneset Lake	—	3.0 µg/L	0.80 µg/L	9.8 m	2023
Finnasvatnet	—	3.0 µg/L	1.3 µg/L	4.7 m	2020
Fjellgardsvatnet	—	3.0 µg/L	1.2 µg/L	7.8 m	2023
Geitvatnet	—	3.0 µg/L	0.80 µg/L	6.0 m	2020
Lundevatnet	—	3.0 µg/L	0.90 µg/L	—	2021
Mjavatn	—	3.0 µg/L	1.2 µg/L	5.2 m	2019
Ostre Bjonevatnet	—	3.0 µg/L	1.3 µg/L	4.4 m	2023
Selbusjoen	—	3.0 µg/L	1.2 µg/L	5.5 m	2023

Showing 20 of 61 named lakes. Open a county or place page for the rest.

Frequently asked questions

Which lakes in Norway are the cleanest?: 61 named lakes in Norway 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 Norway?: The median measured lake in Norway reads 5 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.