Denahm Quarry Lake
Herts and North London, EnglandView mapDirections
EA publishes the water-quality measurements for Denahm Quarry Lake. Here is what has been measured.
- Limited data
Denahm Quarry Lake in Herts and North London, England has official water-quality measurements, shown as reported. Phosphorus: 74.5 µg/L. Chlorophyll-a (algae): 17 µg/L.
How Denahm Quarry Lake is classified
Denahm Quarry Lake 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).
Denahm Quarry Lake is a lake in Herts and North London County, England.
Source: the Environment Agency (England) — not the EPA Water Quality Portal, last sampled 2026-03-05. 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 Denahm Quarry Lake 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 Denahm Quarry Lake
These are the measurements EA publishes for Denahm Quarry Lake. More on the source.
No clarity data. Phosphorus 74.5 µg/L. Chlorophyll-a 17 µg/L. TSI 62.
| 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 | 74.5µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 17µg/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. | 62 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
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Frequently asked questions about Denahm Quarry Lake
Where is Denahm Quarry Lake?
- Denahm Quarry Lake is a lake in Herts and North London, England. This page reports official water-quality measurements, shown as reported.
What is the water quality of Denahm Quarry Lake?
- Denahm Quarry Lake in Herts and North London, England has official water-quality measurements, shown as reported. Phosphorus: 74.5 µg/L. Chlorophyll-a (algae): 17 µg/L.
Is Denahm Quarry Lake safe to swim in?
- Denahm Quarry Lake 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
23 measurements from 1 monitoring station, 2025–2026. Retrieved from the Environment Agency (England; not the EPA Water Quality Portal) on 2026-08-16.
Collected and reported by
- Environment Agency (England)
ea-wqa23 samples · 2025–2026
Monitoring station identifiers (1)
TH-LSN105
Authority classifications are shown as the authority published them. See where the data comes from and data sources.