Where is Lough Coosan?

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

Is Lough Coosan safe to swim in?

Lough Coosan 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 Coosan

Westmeath, IrelandView map Directions

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

Phosphorus

11 µg/L

Less phosphorus than most

Measured by EPA Ireland

Chlorophyll-a

2.9 µg/L

Typical for Ireland

Measured by EPA Ireland

Limited data

See the measurements Directions Where to stay

Lough Coosan in Westmeath, Ireland has official water-quality measurements, shown as reported. Phosphorus: 11 µg/L. Chlorophyll-a (algae): 2.9 µg/L.

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How Lough Coosan is classified

Lough Coosan 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 Coosan is a lake in Westmeath 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 2022-11-17. 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 Coosan 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 Coosan

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

No clarity data. Phosphorus 11 µg/L. Chlorophyll-a 2.9 µg/L. TSI 40.

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	11µg/L	Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential.
Chlorophyll-a (algae)	2.9µg/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.	40	Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic

Low nutrients, clear water. No reading is a swimming clearance.

Ask about Lough Coosan

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

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Stays near Lough Coosan

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Fishing Lough Coosan

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

Frequently asked questions about Lough Coosan

Where is Lough Coosan?: Lough Coosan is a lake in Westmeath, Ireland. This page reports official water-quality measurements, shown as reported.
What is the water quality of Lough Coosan?: Lough Coosan in Westmeath, Ireland has official water-quality measurements, shown as reported. Phosphorus: 11 µg/L. Chlorophyll-a (algae): 2.9 µg/L.
Is Lough Coosan safe to swim in?: Lough Coosan 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

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

Collected and reported by

European Environment Agencyeuropeanenvironmentagenc7 samples · —

Analytical methods

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

Monitoring station identifiers (1)

IRL00351

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