The amount of sewage that was left to flow into the Thames in 2023 was almost five times more than the previous year, it has been revealed.
Between April and December 2023, Thames Water released sewage into London's waterways for 6,590 hours, 11 minutes and 54 seconds.
In just six days, between 25 December and 31 December 2023, sewage was dumped across the Thames Water network for 128 hours and 12 minutes – this is equivalent to 18 hours every day.
These figures are based on City Hall analysis of published Thames Water data, which monitors discharge from 118 sites across the network.
Mayor Sadiq Khan has sent a letter to the new Thames Water CEO Chris Weston, saying “the state of our rivers is an appalling advert for privatisation”.
“London’s rivers hold a special place in the hearts of those of us lucky enough to call this city home,” he added.
Thames Water stressed that 2022 was a drought year, meaning its sewage treatment works were less affected than they were during the wet weather in 2023.
Mr Khan singled out River Wandle, which was the last of the capital’s rivers to lose its “good” status under the EU Water Framework Directive.
He said he was “dismayed” that work to protect Wandle from sewage spills may only begin in 2035.
Mr Khan went on: “London’s rivers hold a special place in the hearts of those of us lucky enough to call this city home.
“I, myself, have many fond memories of walking alongside the Wandle with my family.
“As one of our few treasured chalk stream rivers, it is a truly precious asset, and I am deeply disappointed on behalf of Londoners that you have inherited an approach that is not prioritising its restoration.”
In a statement, the mayor also urged the Government to get onboard.
He said: “London’s rivers are the arteries of our city. Frankly the current state of some of our rivers is appalling and only getting worse.
“Thames Water urgently need to up their up their game, and get a grip of the situation. At the same time, ministers are standing by and letting more and more dirty sewage flow into our rivers.
“We need tougher legislation that forces water companies to act as a matter of urgency.”
In the Mayor’s 2018 London Environment Strategy, he set a target for ten kilometres of rivers to be restored by 2025 and 40 kilometres by 2050. The 2025 target has been met.
But Mr Khan said: “While we’re making huge progress cleaning up London’s air and much of the capital’s environment, it’s a scandal that levels of sewage in our rivers are increasing at the same time.”
Thames Water said: "We regard all discharges as unacceptable and are committed to reducing the need for them.
“Storm 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 are working hard to make these discharges unnecessary and have published plans to upgrade over 250 of our sewage treatment works (STW) and sewers to treat the high volumes of incoming sewage and reduce the need for overflows during wet weather.
"In addition, we have started the £100 million upgrade of Mogden sewage treatment works, which will increase capacity and reduce the number of storm discharges from the site, and we’re also spending £145 million upgrading Beckton sewage works.”A spokesperson also added that that the Thames Tideway Tunnel, a £4.5 billion investment, is nearing completion.
This scheme, combined with other projects, is set to capture 95% of the volume of untreated sewage currently entering the tidal Thames in a typical year.
