Q&A

We are planning to invest £340 million to build a new reservoir in Havant, Hampshire. It is being built in collaboration with Southern Water and will help secure more reliable and resilient water resources for our area and the wider South East.

The South East, as a whole, is under ‘serious water stress’ and water companies are being asked to take less water from some of their sources – such as the chalk rivers in Hampshire – to keep them healthy and protect wildlife. 

At the same time, water companies need to find more water to cater for the effects of climate change and a growing population. 

This major change is going to particularly affect Southern Water, which needs to find new water resources for the customers it supplies drinking water to in Hampshire, to replace water taken currently from the River Test and the Itchen.

In Portsmouth Water's area, there are underground springs which provide plentiful, clean water. In winter, much of this water is surplus to requirements and flows out to sea, so we could make better use of some of it by capturing it and storing it in the reservoir until it’s needed. 

This will allow us to share more water with Southern Water’s customers in Hampshire from our network and increase the resilience of water supplies in the South East.

We already have agreements to share up to 30 million litres of water a day with Southern Water (in West Sussex and Hampshire).

We can share a further nine million litres a day from 2024 from other sources (Hampshire)

We can provide an extra transfer from a mix of sources when the reservoir is built, up to 21 million litres a day (to Hampshire)

The total would be up to 60 million litres of water per day provided to Southern Water.

Overall, building the reservoir would make the whole South East much more resilient to droughts, which are likely to happen more often in the future due to climate change.

We first received planning permission for the reservoir back in 1964 and we carried out a lot of work towards a new planning application in 2008.

However, at the time there wasn’t enough demand for the water, either from our customers or across the South East.

Since then, Southern Water has agreed to reduce the amount of water it takes from the Rivers Test and Itchen in Hampshire, to protect the environment, so they need to find new sources.

As a result, we’re now working in partnership with Southern Water to go ahead with the reservoir to secure more reliable water supplies for the region as a whole. It will also help cater for a growth in the population and housing and more droughts as a result of climate change.

The reservoir will be able to hold about 8.7 billion litres of water when full and supply an average of 21 million litres of water each day.

That’s enough water to supply about 160,000 people during an average year.

As well as being supplied with water from the reservoir, our customers will have the benefit of a new community leisure facility on their doorstep. There will also be a host of environmental benefits locally.

The reservoir site will create a new, healthy and safe place for people to visit – with footpaths for walking, as well as routes for cycling and horse riding, facilities for bird watching, picnic and play areas and car parking.

There will be a visitor centre with a café, toilets and space for community and education activities.

Our proposals for the site so far have been developed over many years with local communities, young people and organisations such as Staunton Country Park and Forestry England.

Building the reservoir will allow us to share water supplies with households in Hampshire (outside of our supply area) who receive their drinking water from Southern Water and where there is a severe shortage.

This means Southern Water’s customers will have reliable water supplies and less water will need to be taken from the River Test and River Itchen, which will be better for the environment.

Our customers in Hampshire who we supply water to are also customers of Southern Water for their wastewater services, so everyone in the area will benefit from the community and leisure facilities at the reservoir.

It will cost about £340 million to plan, build and fill the reservoir with water.

The scheme will be funded by payments from Southern Water to purchase the water it needs to supply its customers. Southern Water has considered a number of options to supply water to its customers and the reservoir is considered to be good value.

Only Southern Water customers who receive drinking water supplies from them will have the cost of the reservoir reflected in their bills. So, this does not include our customers who receive drinking water from us and wastewater services from Southern Water.

This will be the first new reservoir to be built in the South East since the 1970s.

The Government is calling for water companies to invest in more projects to help supply water, such as reservoirs and regional transfers. Projects like this are needed to secure reliable water supplies for the future, alongside reducing the amount of water lost through leaks and encouraging people to use less water.

This will help the country tackle extremes in weather such as droughts, which are likely to happen more often and be more serious as our climate changes. It will also help us provide water supplies to more customers in the future as the population grows in the UK.

The reservoir was selected as part of work carried out by the Water Resources South East (WRSE) group(External link), which includes six water companies in the region and their regulators. It is one of eight ‘big ticket’ schemes which could deliver more than 15 million litres of water each day.

The reservoir is the first regional scheme of this type to be developed in collaboration between two companies (Portsmouth Water and Southern Water) for the greater good of the region.

As well as securing drinking water supplies and creating new homes for wildlife, the reservoir has the potential to become a new leisure and community focus point for Havant.

We’ve been working hard to involve the local community in every stage of this exciting opportunity, such as the public consultation we ran during May and June 2020. During this, hundreds of people were able to find out about our updated plans and have their say – feedback that helped shape the planning applications we submitted to Havant Borough Council and East Hampshire District Council.

In August 2020, we published our ‘You said, we did’ report(External link)(External link), summarising what people told us during the consultation and how we’re responding to the points raised. The reservoir planning application documents are available to view on the councils’ planning web-pages, plus you can download our Havant Thicket Reservoir Design & Access Statement.

Our plans also continue to be shaped by the 70+ members of our Havant Thicket Reservoir Stakeholder Advisory Group, which was established in 2004. The group is made up of representatives from a range of organisations, including local councillors and community and environmental groups. You can view the presentations and minutes from the regular stakeholder group meetings via our Library page.

As well as visiting this website, you can stay in touch with the reservoir project’s progress in the following ways

• Following us on social media via our reservoir Facebook page(External link)(External link) or updates on X(External link)(External link)
• Sign up for our regular e-newsletter(External link)(External link).

Get in touch if you’d like to find out more or be involved.

Schools and education

The reservoir project offers fantastic opportunities for education locally – not only when the reservoir is complete, but also during the planning and construction stages.

Local pupils have been involved since the start of the project, with local young people providing feedback during both our 2008 and 2020 public consultations.

And as the reservoir progresses, the reservoir will become a great venue to learn about the water cycle, climate change, the environment and wildlife, and STEM subjects (Science, Technology, Engineering and Maths).

We’re also involving young people in our environment work to grow and plant trees and hedgerows.

When built, school parties will be welcome at the reservoir to use the education space, bird hides, interpretation boards and the leisure facilities.

There’s lots more information on this website, where you can also give us your questions and comments using the 'Ask us a question' tool on each page. 

You can also get in touch with us via email, phone or post. See our Get in touch page for more.

It’s important we make the best use of the supplies we already have, so we can leave as much water as possible in rivers and the ground to support our environment and wildlife.

Filling the reservoir with water which would normally flow out to sea in winter is one way to do this but we’re also planning to become more efficient with our existing supplies - such as further reducing leaks from pipes and supporting customers to use water more efficiently. This includes providing households with smart water meters, so people can clearly understand how much water they're using.

For more details, please read our new Water Resources Management Plan for 2025-75(External link).