Plans for an 8.7 billion litre storage reservoir spanning 160 hectares, some of it ancient woodland, between Rowlands Castle and Leigh Park has been granted permission to go ahead by neighbouring local authorities.

The detailed planning application by Portsmouth Water for the reservoir is in woodland known as Havant Thicket.

The application, along with a separate one for the pipeline which is needed to fill and remove water to supply to customers, was granted permission following hours of debate by councillors at East Hampshire District Council and Havant Borough Council.

During the separate meetings, held at Penns Place and Havant Civic Centre, concerns were heard from The Woodland Trust, Havant Climate Alliance, Friends of the Earth and residents about the removal of ancient woodland.

But despite the loss of these trees, the exceptional benefits would protect unique habitats and precious local chalk streams, the rivers Itchen and Test, the meetings heard.

In parts, the reservoir will be up to 18 metres deep, and will supply an average of 21 million litres of water each day – enough for about 160,000 people during an average year.

The project is a collaboration between Portsmouth Water and Southern Water and will safeguard water resources for years to come for the south east, and it will cost about £120 million to plan, build and fill the reservoir.

Along with the reservoir, there will a visitor and education centre, a picnic and play area and parking for approximately 200 vehicles.

Work on the reservoir access road is to start this year, and the 8.7 billion litre reservoir will be full and all work finished by 2029.

Portsmouth Water has also worked to create an extensive programme to support the environment on and around the site; it will be a permanent wetland with bird-watching facilities.

And around 200 hectares of woodland and pasture will be created to support wildlife.

Government regulators Natural England and the Environment Agency are satisfied that provided the mitigation and compensation strategy is secured and fully implemented, the scheme will deliver a suitable compensation strategy for the loss of irreplaceable habitats.

East Hampshire District Council planning portfolio holder councillor Angela Glass said: “The reservoir will 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.”

Cabinet lead for planning, Hayling seafront strategy and coastal management at Havant Borough Council, Councillor Clare Satchwell, added: “This major project has been talked about in the borough since the 1960s.

“And after a comprehensive report and presentation at Havant’s Planning Committee on June 3, the committee considered the applications for Havant Thicket Reservoir and gave permission, subject to completion of a Section 106 legal agreement.”

The reservoir and its surrounding green areas measure about one mile (1.6km) in length from east to west, and half a mile (0.8km) from north to south.

It will also be a valuable leisure area for local people and visitors from further afield, says Portsmouth Water chief executive Bob Taylor.

He added: “It is great news that Havant Borough and East Hampshire District’s planning committees granted permission for our reservoir proposals – recognising the growing public need for reliable and resilient water resources and our ambitions and commitment to support the environment and communities.

“As well as securing much-needed future water supplies, Havant Thicket Reservoir will help safeguard the River Itchen and River Test, two of Hampshire’s rare and world-famous chalk streams, by enabling less water to be taken from them.

“It will also create a new green leisure hub for people and wildlife.

“I would like to thank the councils for their support on this vitally-important scheme.

“And we’re also very grateful to local people and community representatives for their strong backing and valuable feedback over a number of years, which have helped shape the plans and our approach in many areas.”

Final legal commitments for the reservoir scheme will now be agreed with both authorities and full permission could be granted by early summer.

Work would then begin – with further environmental work to support wildlife mitigation.

Havant Thicket Reservoir could then open fully to the public in 2029.

Havant Borough Council also granted outline permission for further earthworks and built infrastructure around the reservoir, and for a pipeline to fill it with surplus water from the Bedhampton Springs in winter.

For more information about the reservoir and surrounding leisure area visit www.portsmouthwater.co.uk/havant-thicket-reservoir