Rivers, rain, overflows and spills

On an average rainy day in England, about 2 million litres of rainwater will fall on every square kilometre.  But the rain we’re experiencing isn't ‘average’, in fact it’s officially described as ‘significant’ with 35% more rain than the year before in the Midlands, and seven named storms in four months alone!  And all that water needs to go somewhere.  

Together with the wastewater from your toilets, bathrooms and kitchens, we take away much of this rainwater.  Like many countries around the world, the UK has a combined sewerage system – so rainwater and wastewater goes in the same pipes.

Our sewerage system is usually only about 10% full. But sometimes - after heavy rainfall, for example – there’s just so much extra water going in. Remember that 2 million litres on every square kilometre?   

If the sewerage network gets full, hundreds of thousands of homes and businesses across our patch are at risk of flooding. So, like lots of other places, in the UK we have Storm Overflows (SOs) – which allow some water to drain away to rivers and streams when there’s too much in the system. We’ve got 2,472 of them across the Severn Trent region as we’re landlocked.  

Most of what comes out of an SO when it spills is rainwater.

In 2023 there was about one-third more rain in the Midlands than the year before. And more rain means more water for us to drain away, so SOs will have been working for longer.  

The other thing that changed last year was that we could measure spills at all our SOs for the first time. In December 2022 we finished fitting monitors to 100% of SOs (one of the first UK water company to do this). There’s so much more information (about 300m pieces of data every year to be precise) in 2023 compared to 2022.  

Put simply, last year there was more rain, and we were looking at every SO. The year before was drier and we couldn’t see what each SO was doing.  

There are lots of things affecting river health, not just water companies. In fact, in your region we’re not the main reason why rivers might not be healthy. But we still want to reduce spills.  

The way SOs work are an outdated way of doing things and we don’t want to rely on them any more to keep homes flood-free.  So, we are on a mission to essentially re-plumb how the system works.  This will take some time to do, but we’re doing this faster than what is being asked of us and we’ve got the investment from our shareholders to do it too.  

Over the next few years we’re putting £billions into our Storm Overflow Action Plan (SOAP). Wherever you live across our patch, you’ll see changes. Whether that means upgrading sewage treatment plants, increasing rainwater storage, or even improving SOs themselves.  

That means a system that can deal with these significant rainstorms, that are starting to become the norm due to the changes to climate. So your homes protected from flooding. And, of course, healthy rivers and streams for all of us to enjoy.  

We’re going to keep talking about river health. It’s important and we will work to get this right.   

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