Derwentwater
Cumbria and Lancashire, EnglandView mapDirections
EA publishes the water-quality measurements for Derwentwater. Here is what has been measured.
- Limited data
Derwentwater in Cumbria and Lancashire, England has official water-quality measurements, shown as reported. Phosphorus: 7.9 µg/L. Chlorophyll-a (algae): 3.5 µg/L.
How Derwentwater is classified
Derwentwater in England 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 Environment Agency (England).
Derwentwater is a lake in Cumbria and Lancashire County, England.
Source: the Environment Agency (England) — not the EPA Water Quality Portal, last sampled 2026-05-14. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Derwentwater is safe to swim in today is a call for the Environment Agency (England) and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Derwentwater
These are the measurements EA publishes for Derwentwater. More on the source.
No clarity data. Phosphorus 7.9 µg/L. Chlorophyll-a 3.5 µg/L. TSI 38.
| 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 | 7.9µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 3.5µg/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. | 38 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
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Frequently asked questions about Derwentwater
Where is Derwentwater?
- Derwentwater is a lake in Cumbria and Lancashire, England. This page reports official water-quality measurements, shown as reported.
What is the water quality of Derwentwater?
- Derwentwater in Cumbria and Lancashire, England has official water-quality measurements, shown as reported. Phosphorus: 7.9 µg/L. Chlorophyll-a (algae): 3.5 µg/L.
Is Derwentwater safe to swim in?
- Derwentwater 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
160 measurements from 1 monitoring station, 2016–2026. Retrieved from the Environment Agency (England; not the EPA Water Quality Portal) on 2026-08-16.
Collected and reported by
- Environment Agency (England)
ea-wqa160 samples · 2016–2026
Monitoring station identifiers (1)
NW-88010014
Authority classifications are shown as the authority published them. See where the data comes from and data sources.