Thames Water has discharged more sewage near a nature reserve in Marlow after a similar incident killed fish and put protected wildlife at risk last month. 

Thames Water discharged sewage into the River Thames near the Little Marlow Sewage Treatment Works in Marlow for around 12 hours between Wednesday, March 13, and Thursday, March 14, according to data from the company's event duration monitoring (EDM) storm discharge map.

A similar discharge was reported by the EDM map in Little Marlow on February 9, with members of the local environmental group Wild Marlow spotting dead fish near Spade Oak Lake Nature Reserve in the wake of the "catastrophic" spillage.

Speaking last month, a spokesperson for the group said: “This is such an important area for wildlife. Our water vole project team regularly spots signs of protected species using these waterways, and that wildlife is now at risk.

“Do we have to wait for the River Thames to be declared ecologically dead again before something is done?”

TV presenter and naturalist Steve Backshall, who lives near Maidenhead, also hit out at the water company following the discharge in February.

He said: “For days after a big outage, the stench is unbearable (and) the effect lasts for months afterwards.

“Anglers, dog walkers and birders are wading around in human filth, and who knows what the dogs will be eating. Enough is enough!”

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A spokesperson for Thames Water said they “regard all discharges as unacceptable” and cited several reasons why their sewers across the region have been “struggling to cope” in recent months.

“Many of our sewer systems have been impacted by the higher-than-average long-term rainfall across London and the Thames Valley, with groundwater levels also normal to exceptionally high for the time of year.

“All these issues combined mean there is nowhere for further rain or other flow from nearby land to go.

“The overflows are designed to operate automatically when the sewer network is about to be overwhelmed, which then releases diluted wastewater into rivers, rather than letting it back up into people’s homes.

“We have published plans to upgrade over 250 of our sewage treatment works and sewers across the Thames Valley, including Little Marlow Sewage Treatment Works which is expected to be completed in 2027. This will improve our ability to treat the high volumes of incoming sewage and reduce the need for overflows during wet weather.”