Where is Lough Castlebar?

Lough Castlebar is a lake in Mayo, Ireland. This page reports official water-quality measurements, shown as reported.

Is Lough Castlebar safe to swim in?

Lough Castlebar has official nutrient and clarity measurements, not a bacteria swim class and not a safety clearance. Algal blooms, currents, and depth are not covered. Always check local notices before swimming.

Lough Castlebar

Mayo, IrelandView map Directions

EPA Ireland publishes the water-quality measurements for Lough Castlebar. Here is what has been measured.

Phosphorus

16.5 µg/L

Typical for Ireland

Measured by EPA Ireland

Chlorophyll-a

2.5 µg/L

Typical for Ireland

Measured by EPA Ireland

Limited data

See the measurements Directions Where to stay

Lough Castlebar in Mayo, Ireland has official water-quality measurements, shown as reported. Phosphorus: 16.5 µg/L. Chlorophyll-a (algae): 2.5 µg/L.

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How Lough Castlebar is classified

Lough Castlebar in Ireland is published with the authority's own measurements and class. The measurements here are published by the agency that samples the lake, as reported. Sampling here has recorded phosphorus and algae (chlorophyll-a), but not water clarity.

LakeQuality publishes no grade of its own beside it. Everything below thathas been measured is reported on this page.

Monitoring: the Environmental Protection Agency of Ireland, via UNEP GEMS/Water, with WFD lake names from EPA Ireland.

Lough Castlebar is a lake in Mayo County, Ireland.

Source: the Environmental Protection Agency of Ireland, via UNEP GEMS/Water, with WFD lake names from EPA Ireland — not the EPA Water Quality Portal, last sampled 2022-10-05. Methodology: how these readings are compared.

Swimming conditions

No reading

Limited data

Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.

Whether Lough Castlebar is safe to swim in today is a call for the Environmental Protection Agency of Ireland, via UNEP GEMS/Water, with WFD lake names from EPA Ireland and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.

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Water quality measurements for Lough Castlebar

These are the measurements EPA Ireland publishes for Lough Castlebar. More on the source.

No clarity data. Phosphorus 16.5 µg/L. Chlorophyll-a 2.5 µg/L. TSI 42.

Water quality readings
Measure	Reading	Where it sits
Water clarity (Secchi depth)		No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer.
Total phosphorus	16.5µg/L	Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential.
Chlorophyll-a (algae)	2.5µg/L	Measured, not scored The green pigment in algae — a direct measure of how much algae is in the water.
Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a.	42	Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic

Moderate nutrients, good water quality

Ask about Lough Castlebar

Answers come straight from the public measurements and survey records on this page.

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Stays near Lough Castlebar

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Fishing Lough Castlebar

→ Lough Castlebar fishing regulations (limits, seasons, special rules)

Frequently asked questions about Lough Castlebar

Where is Lough Castlebar?: Lough Castlebar is a lake in Mayo, Ireland. This page reports official water-quality measurements, shown as reported.
What is the water quality of Lough Castlebar?: Lough Castlebar in Mayo, Ireland has official water-quality measurements, shown as reported. Phosphorus: 16.5 µg/L. Chlorophyll-a (algae): 2.5 µg/L.
Is Lough Castlebar safe to swim in?: Lough Castlebar has official nutrient and clarity measurements, not a bacteria swim class and not a safety clearance. Algal blooms, currents, and depth are not covered. Always check local notices before swimming.

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Where this data comes from

12 measurements from 1 monitoring station, 2018–2022. Retrieved from UNEP GEMS/Water GFQA (not the EPA Water Quality Portal) on 2026-08-16.

Collected and reported by

European Environment Agencyeuropeanenvironmentagenc12 samples · —

Analytical methods

GEMStat OPEN / CC BY 4.0
EPA Ireland WFD lake waterbodies CC BY 4.0

Monitoring station identifiers (1)

IRL00453

Authority classifications are shown as the authority published them. See where the data comes from and data sources.