In partnership with
Southern Water Services
Communities across Hampshire and the Isle of Wight have been clear: they want cleaner rivers and coastlines, and they want to see real, sustained progress. We know trust has to be rebuilt and we’re determined to take on the challenge and set Southern Water on a path to help create cleaner rivers and healthier seas. That’s why we are taking urgent, practical action to reduce storm overflows and protect the places we all care about.
At Southern Water, we’re now one year into our £1.5 billion Clean Rivers and Seas Plan. This investment is focused on tackling the root causes of storm overflows, preventing rainwater and groundwater from entering the sewer network in the first place, so that we can make lasting improvements. Whilst there is still a long way to go, early results show that this approach is working - over the past 12 months, more than 700 storm overflow releases have been prevented across our region.
In Hampshire and the Isle of Wight, we will invest £341m over the next five years to reduce discharges from just under 100 storm overflows. This isn’t simply a programme of building larger pipes and tanks. Most of our programme is a hybrid mix of catchment solutions optimising existing systems, new green infrastructure and upgrading of assets. These are designed to reduce storm overflows, support biodiversity and create more resilient local environments.
That means working with natural processes as well as engineering solutions: sustainable drainage schemes that slow surface water before it enters the network; constructed wetlands that filter and store flows; sewer sealing to reduce groundwater infiltration; and smart controls that optimise capacity during heavy rainfall. In Portsmouth Harbour, a £170m programme is combining sewer diversions with sustainable drainage and surface water reduction from homes and businesses. Meanwhile in Cowes, Isle of Wight, targeted pipework upgrades and smart sewer gates have already prevented 57 releases.
We are also working directly within communities. More than 200 roof separations have been completed, removing surface water from the foul sewer system, with further properties currently in progress. Across Pan Parishes, 4.5km of sewer sealing has reduced groundwater infiltration – an often unseen but significant contributor to overflow activity.
There is no one-size-fits-all answer; every catchment behaves differently. That’s why we’ve invested in pathfinder projects over the past two years to test a wide range of approaches. We now have a clear understanding of what works best in different environments, and we’re scaling up those solutions.
This is a complex, nationwide challenge, made harder by climate change and population growth. But early results show that sustained, focused action is beginning to make a difference. There is much more to do, and by accelerating delivery and working closely with communities and partners, we’re building the long‑term resilience needed to create healthier waterways across Hampshire and the Isle of Wight.
Nick Mills, Director of Environment & Innovation, Wastewater, Southern Water.
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