Theo Thomas runs London Waterkeeper, an independent charity set up to challenge polluters and protect rivers in the capital and beyond. The organisation aims to transform the city’s relationship with its rivers, including ensuring we have a swimmable Thames. In this guest blog, Theo calls for Thames Water to do more to make information available about sewage spills.

Data swamps our lives and we need to make it work for us. It must inform our choices and shift the balance of power in our favour. Key to this is environmental information. Worryingly much of this information is hidden away, denying us the ability to make empowered choices. Like how to avoid swimming in a river contaminated with sewage. London Waterkeeper needs your help to make sure we are told when sewers overflow into the River Thames. When we have this we will be closer to a Thames that is truly swimmable.

Many of our sewers combine rainfall drainage with waste water from homes and businesses (i.e. combined sewers). Under certain conditions (usually extreme rainfall events), the volume of sewage is too much for the system. Excess sewage is (legally) discharged into the environment through combined sewer overflows (CSO). We want to know when these discharges are happening.

Currently there is an information vacuum. I did an Environmental Information Regulations request for the Thames between Richmond and Putney. There are 35 combined sewer overflows but only 12 are monitored. No one has any idea of the volume of sewage that spews from any of these pipes when they can’t cope. Thames Water isn’t unusual in this, it’s the same for other water companies, but it’s not good.

It was clear this situation couldn’t continue. The Government has set water companies the deadline of 2025 to fit real-time monitors to 80% of Combined Sewer Overflows (it was originally meant to be 2020). To meet this deadline Thames Water is going to spend part of a £1 billion technology budget on Event Duration Monitors. This will help it better understand how its network is performing and manage it more effectively. This is great, but won’t be enough to do what London Waterkeeper wants to see. This new information must be in the public domain; online and in real-time. That’s what the law says too. London Waterkeeper used the law to change Thames Water’s position and get it to agree in principle to tell people when its sewers spill into rivers. They also committed to develop a water quality alert system, which is going to be piloted downstream of Henley-on-Thames.

I’ve experienced the benefits of this kind of system in Copenhagen. Their website meant that my family didn’t swim in sewage on holiday two years ago. It was a sunny day but the red icon on the Islands Brygge Harbour Bath told us the sewers had overflowed the day before. Without that information there’s a high chance my wife and sons and I would have been sick. The fact that this water quality information is available to the public has transformed the city’s relationship with its water. People know when they have a greater risk of coming into contact with sewage and when they don’t. The new outdoor swim zones are now the most popular open spaces in the summer.

Water companies improving what they know about their own sewers is great, but it’s just the first step. There’s a real risk that they won’t put this information in the public domain, unless they are made to. That’s why we have the Environmental Information Regulations. London Waterkeeper is the first to use the section that refers to the data having to be online, in real-time. The fact Thames Water has committed to publishing its sewer spills in real-time is very welcome, but the law is our guarantee, we’re not simply relying on the good-will of the company.

London Waterkeeper is working with Thames Water to secure public sewer notifications, we’ll never take money from them, but we’re happy to make sure they meet their legal duty.

If people want to see a swimmable Thames, and want to see water companies do what the law says, we need your help. London Waterkeeper needs a louder voice. We are the independent voice for London’s rivers, and it needs to be heard. Support us here – londonwaterkeeper.org.uk/become-a-london-waterkeeper-guardian