Meeting demand and protecting ecosystems with new reservoir storage in East Hampshire
At a glance
The Havant Thicket Reservoir is the first new major reservoir to be built in the United Kingdom (UK) for more than three decades. Developed by Portsmouth Water and Southern Water, the project strengthens regional water security across Hampshire and the South East by creating a shared supply for both utilities. The reservoir will also reduce abstraction from vulnerable chalk streams, safeguarding habitats and biodiversity while forming part of a long-term approach to sustainable water management.
The challenge
Portsmouth Water and Southern Water needed a new strategic water resource that could strengthen supply resilience as demand and drought risks increased. Existing abstraction from the region’s chalk streams, particularly the River Test and River Itchen, was no longer sustainable. Regulators required a solution that balanced a reliable water supply with environmental protection.
The project’s complexity was not limited to the reservoir itself. The site spans 160 hectares and includes supporting infrastructure such as pipelines, pumping stations and treatment works. The design also had to respect the area’s natural springs — some of Europe’s largest sources of high-quality spring water — and account for surplus water flows that would otherwise run out to sea.
Our response
Working directly for Future Water MJJV, we provided multidisciplinary civil and structural design support from concept to planning and approval. Our work helped shape a coordinated plan that combined technical precision with environmental sensitivity.
Our scope included:
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Designing major civil and structural elements such as the valve tower, culvert, spillway and viewing platforms
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Creating detailed designs for connecting roads, wetlands and landscaped areas to support local wildlife and recreation
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Modelling complex water-quality scenarios and proposing aeration systems to maintain reservoir health
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Developing a large control building and supporting the design of two main pumping stations and a booster station
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Integrating features such as wildflower planting, trails and cycle paths to promote community access
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Supporting the Hampshire Water for Life reuse scheme, which transfers recycled water from Southern Water’s network for treatment and potable use
Alongside technical design, we managed environmental impact assessments, conducted archaeological and ecological studies, and engaged closely with local councils and communities throughout planning.
The impact
Construction of the trial embankment and early site works are now underway, with full completion expected in 2028. Once operational, the reservoir will store around 8.7 billion litres of water, enough to supply 21 million litres each day.
Beyond its functional role, the project will transform the surrounding landscape into more than 200 hectares of woodland, pasture and green space, complete with walking and cycling routes, a visitor centre and new habitats for native species. Storing surplus spring water and sharing supplies across networks will reduce pressure on sensitive chalk streams and protect the region’s rare aquatic ecosystems.
For local communities, the reservoir provides secure water alongside new opportunities for recreation, education and connection with nature. As part of a broader regional strategy, it contributes to a resilient and sustainable future for water in the South East.