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 Italy?

The median measured lake in Italy reads 12 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 Italy

Cleanest lakes in Italy: 55 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 Italy

Phosphorus is the nutrient that feeds algae growth, so the lakes at the top of this table are the least loaded ones the Italy monitoring programme has measured. The median measured lake in Italy reads 12 µg/L.

Lake	Place	Total phosphorus	Chlorophyll-a	Secchi	Year
Lago di Truzzo	Sondrio	4.0 µg/L	—	20 m	2018
Lago di Misurina	Belluno	5.0 µg/L	1.1 µg/L	4.0 m	2025
Lago di Montespluga	Sondrio	5.0 µg/L	—	6.5 m	2021
Lago di Santa Croce	Belluno	5.5 µg/L	2.4 µg/L	3.0 m	2025
Lago Maggiore	Varese	5.5 µg/L	2.3 µg/L	5.8 m	2020
Lago del Mis	Belluno	6.0 µg/L	1.5 µg/L	3.3 m	2025
Lago di Santa Caterina	Belluno	6.0 µg/L	0.70 µg/L	2.0 m	2025
Idroscalo	Milan	7.0 µg/L	—	2.2 m	2018
Lago di Ganna	Varese	8.0 µg/L	1.9 µg/L	2.0 m	2021
Lago di Garda	Verona	8.0 µg/L	2.2 µg/L	8.1 m	2025
Lago di Palabione	Sondrio	8.0 µg/L	—	5.7 m	2019
Lago di Palù	Sondrio	8.0 µg/L	—	8.0 m	2021
Lago del Gallo	Sondrio	8.5 µg/L	—	5.5 m	2021
Lago di Corlo	Belluno	9.0 µg/L	5.0 µg/L	3.4 m	2025
Lago di Alleghe	Belluno	9.5 µg/L	2.0 µg/L	1.4 m	2025
Invaso di Arezzo	Perugia	10 µg/L	—	3.0 m	2024
Invaso di Ridracoli	Forlì-Cesena	10 µg/L	—	—	2025
Lago Brasimone	Bologna	10 µg/L	—	—	2025
Lago di Cadore	Belluno	10 µg/L	4.3 µg/L	2.2 m	2025
Lago di Ghirla	Varese	10 µg/L	—	4.9 m	2021

Showing 20 of 55 named lakes. Open a county or place page for the rest.

Frequently asked questions

Which lakes in Italy are the cleanest?: 55 named lakes in Italy 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 Italy?: The median measured lake in Italy reads 12 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.