A new £340 million reservoir will be built in the UK, and construction work is already underway.
Havant Thicket Reservoir will protect water flowing from the River Test and River Itchen into Hampshire to help with water supply in the area.
Last month, construction work was commenced on the project, the first new reservoir in the UK for the 30 years.
The Havant Thicker Reservoir will hold 8.7 billion litres of water when completed.
It will be approximately a mile long from east to west and half a mile wide from north to south.
It will also come with new footpaths, cycle routes, bridleways and a visitor centre.
In a statement, Southern Water said: ”The UK’s first new reservoir in three decades.
”We’ve broken ground on the UK’s first new reservoir in over 30 years! Due to our growing population, it’s predicted by 2030, we’ll need an extra 50 million litres of water a day to meet demand.
“The new reservoir will hold up to 8.7 billion litres and help secure the future of water for us and future generations.”
It is expected that the new reservoir will be built by 2029.
Southern Water CEO Lawrence Gosden said: “This official launch of the Havant Thicket Reservoir project is an essential part of our plans to create a new resilient water supply for the South East.
“The new reservoir and the planned Hampshire Water Transfer and Water Recycling Project will transform the way we source, treat, and supply water across the county.
“It’s essential that we leave more water in the environment and protect Hampshire’s chalk streams while also catering for climate change and population growth.
“Overcoming these challenges means developing new robust and resilient water supplies for us and future generations.”
Portsmouth Water’s CEO Bob Taylor added: “I am delighted to announce that work to create the new Havant Thicket Reservoir has officially begun.
“As well as breaking ground quite literally here on site, this milestone represents a ground-breaking moment for the water industry as a whole. This is the first major UK reservoir to be constructed in more than 30 years, and I am incredibly proud that Portsmouth Water is delivering the project.
“I would like to take this opportunity to thank everyone who has supported the scheme to date. It’s people who make projects happen and we are fortunate to have so many inspiring and dedicated individuals involved with ours.”