The need to plan for future additional water resources in south-east Hampshire was recognised in 1965 when Portsmouth Water brought 160 hectares of land at Havant Thicket for the construction of a new reservoir. The site lies between Rowlands Castle, Warren Park and Staunton Country Park. It would be about 1 mile from East to West and 0.5 miles North to South.
The geology of the area is critical here and is the reason why the site was chosen. The site is underlain by impermeable clay, including the London Clay which will provide the ideal material to form the reservoir basin and hold water, as it can easily be excavated out and shaped to form the reservoir, with the excavated clay used to form a perimeter embankment high enough to retain a water body which will be up to 20m deep. Much of the natural bowl shape for this is already there. (Click on the image below to enlarge).
The last cost projection for the reservoir project was put together a few years ago when it was estimated that the reservoir and ancillary facilities would cost about £54 Million. Unlike most other water companies Portsmouth Water currently has no raw water storage capacity and the reservoir would provide excellent resilience against drought, future increased housing needs and pollution incidents at other sources. In addition, it could help to meet the needs of other adjacent suppliers who are under greater pressure than Portsmouth Water in relation to their water supply needs. The reservoir could be a very important part of the regional solution to forecast water shortfalls in the south-east.
The water to fill the reservoir will come from the Havant & Bedhampton Springs. Surplus water from the Springs overflows in to Langstone Harbour and there is so much surplus water that the reservoir is expected to fill in just 2 years after diverting some of the surplus water into it.
Portsmouth Water own all of the land required for the reservoir, and are working with the water regulators through the Water Resources in the South East Group to encourage the development of a sustainable strategic solution along the South Coast as they believe the reservoir could be a key part of the measures to provide a sustainable solution to the water shortfalls in the south-east.
Portsmouth Water carried out extensive consultation with local communities, schools and clubs in 2008 to determine what the reservoir might offer beyond just water storage.
One of the first questions was should it be designed for Low, Medium or High usage. The split in views was not clear cut with High getting 31% support, Medium 36% support and Low 33%, which on balance suggested a low to medium level of recreational usage would be preferred. As a result Portsmouth Water propose to include the following:
- A 5k perimeter bridleway, cycling and walking paths,
- Visitor facilities including toilets and information centre (environmental, ecology information), function room, education area, changing area for water sport training uses,
- Bird hides,
- Sanctuary area with Islands for wildlife to safely nest and roost,
- Club use on the water like Scouts, College groups (but not a private sailing club) and
- Spaced out play facilities for children.
Hopefully this project will get to a point where it becomes a fully supported and strategic resource for the south-east and goes ahead. At the moment Portsmouth Water has enough water to meet the needs of people in their supply area.
How would the reservoir be filled? Behind the Portsmouth Water Bedhampton Head Office site there is a natural spring line along a 1km long fissure in the ground. The water rises out of the ground naturally and will be pumped up to the reservoir. When needed the water will return to Bedhampton by gravity, no pumping will be needed. A pipeline would need to be built from the springs to the reservoir.
How clean is the water? It has been filtered as it passes through the chalk and provides very high quality water at very low cost. Currently the surcharge is discharged into the harbour. Portsmouth Water can not divert all of the surplus water as a minimum flow to Langstone Harbour must be maintained to provide freshwater for birds to drink and bathe in.
How much water is needed to fill the reservoir? About 8,700 million Litres and it would take approximately 2 years to fill.
How long would it take to build the reservoir? With planning, site preparation, infrastructure, excavation, construction of the facilities, then filling, it will take about 10 years.
How long has this been planned? Portsmouth Water put significant resource into the current plans from 2004 but the site was chosen in the 1960’s and first got planning permission in 1965 (now expired).
How often would it be needed? Based on drought conditions perhaps once in every 10 years. The top 15m of the reservoir could be drawn down leaving 5m in the deeper areas for fish etc. It would then take perhaps 2 years to refill to the original level.
How was the consultation carried out? Letters were sent to 17,000 local residents, information was put in libraries and shops, newspapers, TV and local radio covered the consultation as well as presentations to local organisations, authorities and public exhibitions. Workshops were held in schools.
Here is a link to the full Portsmouth Water Summer 2008 newsletter that details the scheme and the community use: Portsmouth Water 2008 Newsletter