The reservoir is a joint initiative between two water companies,
Portsmouth Water and
Southern Water and, when completed, it will span with an anticipated capacity of . It will supply an average of of water per day and allow Southern Water to reduce the volume it extracts from the rivers
Test and
Itchen (typically annually. However, by February 2026, the expected date of opening was 2031 with an estimated cost of £340 million. The site is bounded to the north by
Havant Thicket, an area of forestry managed by
Forestry England, to the east by
Staunton Country Park and by the Leigh Park area of Havant to the south. It will straddle the border between the
Borough of Havant and
East Hampshire District. The site is underlain by
clay,
silt and
sand of the
London Clay Formation and, in small part, of the
Lambeth Group. The current valley floor is characterised by
head deposits. Inflow of water to the site will be piped from natural springs in the Bedhampton area. This will occur when rainfall is heavy and the water would simply otherwise flow out to the sea. The reservoir is expected to measure from east to west, and be between and north to south. The perimeter will measure and the deepest point will be . Havant Thicket will be the first reservoir to be built in Britain since the early 1990s. ==References==