New information shows a series of sewage spillages were the reason outdoor swimming was suspended for several months at King’s Mill Reservoir.
Statistics published by the Environment Agency reveal there were four spillages into the site, near Sutton-in-Ashfield, in 2022.
Another 40 spillages into the connecting River Maun at Sutton also took place in 2022, the data shows, lasting for more than 186 hours.
In January an outdoor swimming club recorded “erratic” water readings in the reservoir, and halted activities until the summer.
Love Open Water, which runs swimming clubs at the site, said the decision was not “taken lightly” but committed to “continue to invest in water testing to build water quality”.
The site has since reopened to swimmers, the organisation’s website confirms.
Now further information has been revealed in Nottinghamshire County Council’s full council meeting, leading Labour councillors to call for action.
The Environment Agency data, published in April, shows the sewer overflow into the reservoir followed a storm and lasted for a total of just over 18 hours in 2022.
Speaking in the meeting on Thursday (July 13), Councillor Paul Henshaw (Lab), who represents Mansfield West, said: “Part of my division covers the reservoir, which is a beautiful open space and a place for people to walk and to take advantage of the brilliant cafe.
“But we need to make sure open spaces and green spaces are clean spaces and, during the last year, effluent pollution was discharged into the reservoir.
“I don’t think this is acceptable, causes all sorts of problems and denigrates the open spaces when it goes into the River Maun.
“Over the last year, I’ve tried to get a motion to the council asking that we look into this problem and do something about it.
“We have the opportunity to comment on the quality of water in lakes and rivers across Nottinghamshire.
“Let’s get together and tell privatised water companies that discharging [sewage] into lakes and rivers is not acceptable and, in this chamber, try to ensure this doesn’t happen.”
Responding to the sewage discharges, Severn Trent Water said it has a team of river rangers who are active around Sutton-in-Ashfield and Mansfield.
The water company said these rangers recently spent a day working with staff at King’s Mill Reservoir.
It added a £76m Green Recovery Flood Resilience project around the Mansfield area will install sustainable drainage systems around the town, the River Maun and the reservoir.
This, it says, will have the benefit of “reducing storm overflow activations by retaining surface water and delaying or preventing it entering the combined sewer network”.
A Severn Trent spokesperson added: “We understand why people feel let down by water companies when it comes to rivers.
“We know what needs to be done to make it right, and we’re doing it. We’re delivering an industry-leading plan that includes bold commitments, such as by 2030 our operations will cause no harm to rivers.
“In the first year of this plan, we’ve reduced our impact by a third, but we know there’s more to do, which is why we’re continuing to invest hundreds of millions of pounds into making rivers the healthiest they can be.”