If given the go-ahead the Havant Thicket reservoir would be the first to be built in the South East since the 1970s.

The reservoir is being progressed in collaboration with Southern Water, to enable a bulk supply to the neighbouring company’s customers and support them to meet sustainability reductions on two chalk streams – the Rivers Test and Itchenin Hampshire.

Atkins will carry out investigations, assessments and design required to submit an outline planning application in late 2020.

Richard Whale, Water Market Director at Atkins, said: “This is a great opportunity to redefine best practice in reservoir design.

“Collaboration and innovation will play an integral part in the design of the reservoir and its surrounding infrastructure.”

The reservoir is scheduled to be built, filled and operational by 2029. It is set to be the final piece of a jigsaw which will see Portsmouth Water export around 60m litres of water a day to Southern Water.

Bob Taylor, CEO of Portsmouth Water, said: “We’re delighted to have the expertise of Atkins on board for what is a critical water-supply infrastructure scheme for the wider South East as supplies come under increasing pressure from climate change and population growth.

“This market-based project meets the criteria set out by Government and the National Infrastructure Commission to meet future water demand in England and Wales – through storage infrastructure and strategic transfers.

“So, it’s vital we progress this first collaborative initiative to set the path for future investment. Atkins’ support will ensure we can do this.”