A warning has been issued about the risks of open water after a number of visitors fell ill following trips into Southwater Country Park lake.
Horsham District Council says the paddling beach area of the lake remains closed as a precaution while longer-term options for access and use are reviewed.
The council said it is working with the UK Health Security Agency following notifications of illness believed to be linked to people entering the lake since late June.
The lake is rainwater-filled, untreated, and has no inflow or outflow, meaning water quality can vary.
A Horsham District Council spokesperson said: “Horsham District Council, working in conjunction with the UK Health Security Agency (UKHSA), can now confirm that there have been a number of notifications of illness believed to be related to entering the Southwater Country Park lake since 25 June 2026.
“The Council advises that members of the public, if they believe they have been impacted ingesting water from the lake, should report their symptoms to their GP/a medical clinician and inform them that they have been in the lake, to enable their individual case to be reported to the UKHSA and dealt with appropriately.
“The Council wants to emphasise that the lake is an open body of water which is untreated and so water quality is variable.
“The Council took swift precautionary action to temporarily close the paddling beach area of the lake on 29 June when it was advised of the illnesses which could potentially be linked to the lake.
“It has now undertaken due diligence measures and, working with advice from the UKHSA, has undertaken a thorough risk review.
“As a result of this review, the paddling beach area of the lake will remain closed until further notice. The only use of the water can be through the water sports operator, who provides managed access to the lake, based on a thorough risk assessment with mitigations in place. That said, it is recognised that the nature of the lake means that there are still risks associated with ingesting water.
“The Council now wants to re-emphasize the dangers and risks associated with accessing all open water areas that may well contain harmful bacteria which can increase in hot weather conditions.”
Horsham District Council has been responsible for Southwater Country Park for more than 40 years. The authority says this is the first time a decision has been taken to close access due to water safety concerns.
A long dry period, combined with two recent heatwaves, is believed to have helped create conditions in which bacteria can thrive.
The council says the closure period will be used to review longer-term options for the lake.
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