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 South Korea?

The median measured lake in South Korea reads 20.5 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 South Korea

Cleanest lakes in South Korea: 88 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 South Korea

Phosphorus is the nutrient that feeds algae growth, so the lakes at the top of this table are the least loaded ones the South Korea monitoring programme has measured. The median measured lake in South Korea reads 20.5 µg/L.

Lake	Place	Total phosphorus	Chlorophyll-a	Secchi	Year
대아지	—	6.0 µg/L	3.2 µg/L	3.6 m	2025
동화호	—	6.0 µg/L	3.3 µg/L	2.0 m	2025
구천댐	—	8.0 µg/L	2.5 µg/L	2.0 m	2025
부안댐	—	8.0 µg/L	1.8 µg/L	2.5 m	2025
소양강댐	—	9.0 µg/L	1.2 µg/L	3.0 m	2025
용담댐	—	9.0 µg/L	2.8 µg/L	2.5 m	2025
평화의댐	—	9.0 µg/L	0.70 µg/L	0.5 m	2025
감포댐	—	10 µg/L	3.2 µg/L	2.0 m	2025
밀양댐	—	10 µg/L	1.5 µg/L	2.8 m	2025
섬진강댐	—	10 µg/L	2.8 µg/L	2.5 m	2025
성덕댐	—	10 µg/L	3.2 µg/L	3.0 m	2025
충주댐	—	10 µg/L	1.8 µg/L	4.0 m	2025
화천댐	—	10 µg/L	1.5 µg/L	4.5 m	2025
운문댐	—	11 µg/L	2.8 µg/L	2.0 m	2025
장흥댐	—	11 µg/L	3.9 µg/L	2.3 m	2025
합천댐	—	11 µg/L	0.80 µg/L	2.5 m	2025
횡성댐	—	11 µg/L	4.3 µg/L	2.5 m	2025
군남댐	—	12 µg/L	1.4 µg/L	0.9 m	2025
담양댐	—	12 µg/L	3.3 µg/L	2.5 m	2025
동복댐	—	12 µg/L	5.8 µg/L	2.0 m	2025

Showing 20 of 88 named lakes. Open a county or place page for the rest.

Frequently asked questions

Which lakes in South Korea are the cleanest?: 88 named lakes in South Korea 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 South Korea?: The median measured lake in South Korea reads 20.5 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.