Grafham Water Reservoir
Cambs and Bedfordshire, EnglandView mapDirections
EA publishes the water-quality measurements for Grafham Water Reservoir. Here is what has been measured.
- Limited data
Grafham Water Reservoir in Cambs and Bedfordshire, England has official water-quality measurements, shown as reported. Phosphorus: 236.5 µg/L. Chlorophyll-a (algae): 10.2 µg/L.
How Grafham Water Reservoir is classified
Grafham Water Reservoir 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).
Grafham Water Reservoir is a lake in Cambs and Bedfordshire County, England.
Source: the Environment Agency (England) — not the EPA Water Quality Portal, last sampled 2026-07-23. 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 Grafham Water Reservoir 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 Grafham Water Reservoir
These are the measurements EA publishes for Grafham Water Reservoir. More on the source.
No clarity data. Phosphorus 236.5 µg/L. Chlorophyll-a 10.2 µg/L. TSI 68.
| 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 | 237µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 10.2µg/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. | 68 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
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Frequently asked questions about Grafham Water Reservoir
Where is Grafham Water Reservoir?
- Grafham Water Reservoir is a lake in Cambs and Bedfordshire, England. This page reports official water-quality measurements, shown as reported.
What is the water quality of Grafham Water Reservoir?
- Grafham Water Reservoir in Cambs and Bedfordshire, England has official water-quality measurements, shown as reported. Phosphorus: 236.5 µg/L. Chlorophyll-a (algae): 10.2 µg/L.
Is Grafham Water Reservoir safe to swim in?
- Grafham Water Reservoir 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
83 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-wqa83 samples · 2016–2026
Monitoring station identifiers (1)
AN-22M18A
Authority classifications are shown as the authority published them. See where the data comes from and data sources.