Cosmeston Lakes Water Quality information
What’s the water quality like at Cosmeston Lakes?
Your safety is our top priority. The Aqua Park only opens when water quality meets recognised safety standards and conditions are safe for activities to take place.
During the spring of 2025, a professional scuba diving team has surveyed the lakebed where the Aqua Park is located, in conjunction with a bathymetric depth survey, to confirm that there are no objects under the surface and that the water depth is suitable (3m – 12m).
Our water samples are tested and analysed by Public Heath Wales at their UKAS-accredited laboratory.
We take two samples at the same time and from the same location on the Aqua Park, which are tested side by side. This helps us identify any potential sampling or laboratory errors, as the two results should be very close to each other.
For transparency, the graphs shown on our website display the average of the two results.
Our closure policy is precautionary and always based on the worst result.
We have been taking samples twice a week during the 2025 bathing season to ensure water quality remains safe. Two key indicators are tested:
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- E. coli
- Intestinal Enterococci
These bacteria occur naturally in the gut of humans and animals. Most strains are harmless, but high levels can indicate pollution and may pose a risk if swallowed.
We follow guidance given directly to us by Swim England, who have stated that there should be no swimming when results are above the levels below. These are the same fail levels as World Aquatics and The Aqua Park Association, following national and international governing bodies
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- 1,000 CFU/100ml for E. coli
- 400 CFU/100ml for Intestinal Enterococci
Aqua Park Sessions may only resume once subsequent testing has shown results are below these thresholds.We also adopt many of the principles of the World Aquatics testing regime, alongside the requirements of our own industry body, the Aqua Park Association, which accredits Aqua Parks across the UK. These same standard levels are applied across the country to a wide range of open water recreational activities, from Aqua Parks to open water swimming and even designated inland bathing waters.
The graphs show bacteria levels over time, measured in colony-forming units (CFU) per 100ml.
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- The red line shows the Fail threshold.
Beneath the red is considered Good Quality - The green line shows the Excellent threshold. All our results from the 2025 bathing season are published here. To date, the water has consistently met the standards required for safe bathing.
- The red line shows the Fail threshold.
What about the wildlife at Cosmeston Lakes?
A detailed ecological assessment, undertaken by local firm Acer Ecology, has confirmed that the seasonal Aqua Park at Cosmeston Lakes Country Park will have no significant negative impact on local birdlife or water vole populations.
The Aqua Park will be situated away from sensitive bird nesting areas, further reducing any potential for disruption. The eastern lake, already supports a range of recreational activities such as paddleboarding, sailing, dog walking and scuba diving.
The study shows that bird species in the area are already well adapted to this level of human activity. Many common bird species show high tolerance to disturbance and are unlikely to be affected by the seasonal operation of the inflatable water park, which are temporary structures.
Extensive surveys and habitat assessments on water voles where carried out, which found that the area proposed for the Aqua Park has limited suitability for water voles. The park will be located on open shoreline lacking the vegetation that water voles rely on, and no signs of burrows or active vole presence were found in that specific zone. As such, the risk of harming water vole populations is considered negligible.
The parks SSSI status is there because of one species of rare underwater plant, starry stonewart, which is only found in the western lake, the eastern lake is formally designated as suitable for recreational activity. The seasonal nature of the attraction, combined with safeguards, that the Aqua Park can operate safely and responsibly whilst maintaining the park’s wildlife conservation goals.
Stop the spread of invasive species. Check – Clean – Dry your equipment and clothing.
Help stop the spread of invasive plants and animals. Personal wetsuit and wetshoe use is is not permitted at Cosmeston lakes, You can help protect the environment and activities you enjoy by keeping your kit free of invasive plants and animals, whenever you leave the water remember to:
Check your clothing after leaving the water for mud, aquatic animals or plant material. Remove anything you find and leave it at the site.
Clean everything thoroughly as soon as you can, paying attention to areas that are damp or hard to access. Use hot water if possible.
Dry everything for as long as you can before using elsewhere.
What should I do with my kit and equipment?
Fo safety reasons, Aqua Park must supply a correctly fitted buoyancy aid, you cannot bring your own.
Personal wetsuit use is not permitted at Cosmeston Lakes.
Personal wetsuit use is permitted at Lakeside and Rutland.
Remember to Check – Clean – Dry to stop the Spread of aquatic invasive species. This poster highlights good practice for water users
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Public Health Wales UKAS accredited lab results for E.coli & Enterrocicci
Average grade of 2 sampes taken
- 01.04.25 Excellent & Excellent
- 09.04.25 Excellent & Excellent
- 11.04.25 Excellent & Excellent
- 15.04.25 Excellent & Excellent
- 16.04.25 Excellent & Excellent
- 22.04.25 Excellent & Excellent
- 28.04.25 Excellent & Excellent
- 01.05.25 Excellent & Excellent
- 06.05.25 Excellent & Excellent
- 09.05.25 Excellent & Excellent
- 12.05.25 Excellent & Excellent
- 13.05.25 Excellent & Excellent
- 16.05.25 Excellent & Excellent
- 19.05.25 Excellent & Excellent
- 22.05.25 Excellent & Excellent
- 27.05.25 Excellent & Excellent
- 30.05.25 Excellent & Excellent
- 03.06.25 Excellent & Excellent
- 04.06.25 Excellent & Excellent
- 09.06.25 Excellent & Excellent
- 12.06.25 Excellent & Excellent
- 13.06.25 Excellent & Excellent
- 14.06.25 Excellent & Excellent
- 17.06.25 Excellent & Excellent
- 19.06.25 Excellent & Excellent
- 25.06.25 Excellent & Excellent
- 27.06.25 Excellent & Excellent
- 01.07.25 Excellent & Excellent
- 03.07.25 Excellent & Excellent
- 09.07.25 Excellent & Excellent
- 16.07.25 Excellent & Excellent
- 21.07.25 Excellent & Excellent
- 24.07.25 Excellent & Excellent
- 28.07.25 Excellent & Excellent
- 31.07.25 Excellent & Excellent
- 31.07.25 Excellent & Excellent
- 04.08.25 Excellent & Excellent
- 07.08.25 Excellent & Excellent
- 11.08.25 Excellent & Excellent
- 14.08.25 Excellent & Excellent
- 18.08.25 Excellent & Excellent
- 21.08.25 Excellent & Excellent
- 26.08.25 Good & Excellent
- 28.08.25 Excellent & Excellent
- 02.09.25 Excellent & Excellent
- 04.09.25 Excellent & Excellent
- 11.09.25 Excellent & Excellent