Thames Water is in a financial mess, but it’s also the focus of growing public concern – and anger – over its seemingly increasing inability to manage its day-to-day responsibilities, most notably by continuing to pump large amounts of raw sewage into London’s waterways on a regular basis.
A five-fold increase in the amount of sewage released into the capital’s rivers between 2022 and 2023 was “scandalous”, Sadiq Khan said earlier this year, while just last week Thames reported a further 40 per cent rise in “pollution incidents” during the first half of 2024.
Improving water quality was a key part of the Mayor’s re-election pitch in May. He pledged both to press Thames Water for more action and to get his own plan in place to make rivers in London “swimmable within ten years”. So how bad is the state of the River Thames? Who is to to blame, and will Khan’s improvement plan work?
Perhaps the state of the river isn’t as bad as we think. Since 1957, when it was declared “biologically dead”, it has made a “remarkable recovery”, says waterways charity Thames21. In fact, despite the “stubborn perception” that the river is dirty and lifeless, it is currently one of the “cleanest city waterways in the world”, according to the Royal Museums Greenwich.
Fish have returned; the flounder in 1967, salmon in the 1980s, and now more than a hundred species in all. Seals, top predators, can be seen along the length of the tidal Thames, along with keystone bird species such as herons, cormorants, Canadian and Egyptian geese, all attesting to improving water quality.
A comprehensive Zoological Society of London study in 2021 summed up this under-recognised success story as the “re-establishment of a thriving estuarine ecosystem” providing a “rich and varied habitat to an abundance of wildlife, and many benefits to people.” Improved sewage treatment, tighter regulations, action to increase the levels of dissolved oxygen and reduced abstraction and industrial discharges had all played a part.
But it’s not all good news. Everyone now knows about CSOs – combined sewer overflows. Joseph Bazalgette’s sewer network, constructed after the “Great Stink” of 1858, combines rainwater and waste water in the same pipes. To avoid that mixture flooding our homes when the system, designed for a much smaller London population, fills up, the excess is discharged into the river. Sewage dumping, spiking after heavy rain, brings an increase in damaging nitrate concentrations in particular, threatening water quality. Sewage brings human health risks too.
Big improvements are coming, though. The £4.5 billion 25 kilometre-long Thames Tideway Tunnel will intercept some 95 per cent of the untreated sewage currently overflowing into the river through central London when it is fully operational next year. Now partially open, it is already “working as intended, stopping discharges,” Environment Agency London boss Charlotte Wood told London Assembly members last week.
The new “super sewer”, for which customers will be paying around £25 a year for some two decades to come, will be a game-changer. But it won’t get the utility company totally off the hook. There are CSOs upstream on the Thames and in the other 40 rivers in London to be dealt with, plus waste “misconnections”.
And as pressure on the system grows, Tideway is essentially just buying time, with project boss Andy Mitchell himself calling for a different approach in future. “Simply channelling rain into the same pipes and tunnels as our foul water is not a sustainable solution,” he has said . The alternative requires “spongification”, creating many more “rain gardens”, reedbeds and wetlands to soak up excess rainfall and filter waste water naturally. Thames Water has a rain garden programme, but water charities are urging faster action.
It’s not all about sewage. The whole system needs catch-up investment. Thames lost 570 million litres of drinking water a day through leakages last year. There are wider issues too, not least the impact of climate change, bringing damaging rises in water temperatures and more frequent extreme weather, from heatwaves and droughts to more heavy rainfall. This spring was the wettest since 1986.
Climate change brings both an increased risk of flooding and waste overflows, and reduced flows in rivers and aquifer levels – less water when demand is growing. We are running low. Thames forecasts it could need an extra billion litres a day by 2050 and the London Assembly environment committee has warned of seasonal water shortages in the capital.
What needs to be done? The Assembly has called for action on three fronts: reducing leakages, reducing demand for water and boosting supply. That means government intervention – a review of water regulation is already underway – and Thames Water (or its successor) and other agencies working together like never before.
We Londoners can play a part too, by not paving over our driveways and gardens, keeping fat out of our drains, not flushing wet wipes and, critically, using less water, all of which will ease the pressure on the sewers. The Environment Agency advises a limit of 110 litres a day per person, but Londoners currently use 146 litres daily.
So what about the Mayor’s “swimmable in 10 years” plan? It’s a tough and expensive target, given that no London river is officially ranked “good” for water quality, and just four locations – the Hampstead Heath ponds and the Serpentine – have achieved designated bathing status. Guests at last week’s committee meeting expressed some scepticism.
Firstly, the Thames is already “swimmable”, albeit that isn’t advisable after heavy rain. Londoners are regularly getting into the river upstream of Putney Bridge, as well as swimming in more protected and supervised open waters in Docklands and other locations listed in the Mayor’s new outdoor swimming guide.
The current “doom cycle” about how dangerous and “full of sewage” our rivers are should be kept in context too, said Ben Seal, from Paddle UK. “Our rivers have never been clean,” he added. The physical and mental health benefits of outdoor swimming significantly outweighed its “inherent risks”, added Swim England representative Philip Brownlie. The priority should be more information, said Seal, to help river users “make choices, protect themselves, and keep safe”.
Khan hasn’t fleshed out his plan yet, but it’s clear that its about more than swimming. In fact, his most recent statement on the subject didn’t mention swimming at all, focusing instead on restoring nature to the capital’s rivers, to “bring back many more species and improve climate resilience”.
The Mayor will be putting in £30 million over the next three years, building on success stories such as the introduction of beavers in Enfield and Ealing. But he has few direct powers in the area, so it will be mainly down to Thames Water to take – and fund – the action Khan wants to see on sewage spills, misconnections and sustainable drainage.
Nevertheless Khan will be hoping that his proposed coalition, of “companies, government agencies, charities and campaigners” working to get swimming possible in locations such as the Wandle, Lea and Roding rivers, as well as other activities on or by the water, “when it is safe and sustainable to do so”, will focus minds.
Is there a danger though, as industry figures have warned, that the “serious challenge of water security” could be overlooked while we focus on sewage? It’s a concern highlighted at one of Khan’s proposed clean-up sites, at Teddington. This is already well-used by swimmers. Yet Thames Water is controversially planning a £250 million scheme there to boost supply by abstracting river water and replacing it with treated waste water.
Thames say the scheme, provisionally approved by government, is vital for protecting London from the risk of the taps running dry. Campaigners, including local MP Munira Wilson, say it would damage water quality and make the river unsafe to swim in. As Khan finalises what could be a flagship programme for the third-term Mayor and negotiates his targets with Thames and Whitehall, such questions will loom large.
It comes back to money too, with Thames, currently awaiting judgement from the regulator Ofwat on how much it can hike customers’ bills over the next five years, warning that the problems it is facing will “require decades, and substantial amounts of money, to fix”.
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