Solving the UK’s water security challenges

The United Kingdom (UK) is facing rising water security threats after decades of underinvestment in reservoirs and large-scale water infrastructure. Reduced river flows, ecological damage and growing demand are pushing supply into a dangerous imbalance. With billions of litres of water shortfall predicted by mid-century, new reservoirs and transfer schemes are now being brought forward at scale. This article explores the urgency, the emerging programme of works and how we’re contributing to the delivery of projects such as the Havant Thicket Reservoir.

The UK’s water industry has not built a new reservoir in more than 35 years. In that time, reduced flows, over-abstraction and rising pollution levels have strained the nation’s rivers and water bodies. The consequences are clear:

• The National Infrastructure Commission estimates a demand-supply gap of up to 4 billion litres per day by 2050.
• The National Audit Office projects an even higher shortfall: 5 billion litres daily.
• In southeast England, 70 percent of water supply relies on porous chalk streams, with deteriorating conditions.

The urgency is heightened by climate change and population pressures, particularly in the south and southeast, where resources are already less abundant. Rare chalk streams such as the Test and Itchen, long recognised for their ecological importance, have become more vulnerable.

Years of underinvestment are now being addressed with a substantial pipeline of work. The Regulator’s Alliance for Progressing Infrastructure Development (RAPID), formed in 2019 by Ofwat, the Environment Agency, and the Drinking Water Inspectorate, has already encouraged 18 large-scale strategic supply schemes, with more being planned.

The vision for new water assets includes the following:

• Nine new reservoirs.
• Nine major water transfer projects to expand capacity.
• Investment in infrastructure and resources quadrupling to a record £44 billion.
• Three reservoir projects in the pipeline: Fens, Lincolnshire and Southeast Strategic Resource Option (Abingdon Reservoir by Thames Water).
• The conversion of an existing quarry to a reservoir in Somerset.

All these schemes together are expected to produce 670 million litres of extra water per day once completed after 2030. Delivering this vision within tight timeframes will require responsive and reliable technical partners.

Ofwat’s final determinations for Asset Management Period 8, which began in April 2025, confirm expenditure of £104 billion. These schemes are aimed at addressing climate change and environmental challenges, for which the UK’s current infrastructure is ill-equipped.

Among the flagship schemes is Havant Thicket Reservoir, an 8.7-billion-litre-capacity reservoir covering 160 hectares, jointly developed by Portsmouth Water and Southern Water. It is the UK’s first reservoir of its kind in more than three decades.

As lead designer, working with Coffey under contractor Future Water MJJV, our team is responsible for the reservoir’s control building, culvert, valve tower and large-diameter pipework. We’ve managed unforeseen conditions and kept the project on schedule, drawing on our long global experience of delivering water projects where delays are common.

New reservoirs are being designed with environmental considerations at their core. Havant Thicket is not intended to dam a river, but to relieve abstraction pressures on the Test and Itchen chalk streams. The reservoir will be fed initially by springs and supplemented by treated wastewater to maintain ecological balance.

Demonstrating how infrastructure development can be paired with long-term benefits for natural capital and biodiversity, key environmental features include:

• A wetland area along the northern shore, supported by clay substrates to maintain year-round habitat conditions.
• Walking, cycling and horse-riding trails, picnic areas, a play area and a visitor centre for community use.
• Engagement with stakeholders and residents, recognising the role of community support in project approval.

Technical resilience and agility are critical elements of our project delivery. Climate considerations from our global work, such as dam wall raising for irrigation and power generation, are informing design decisions at Havant Thicket. As are some of our other recent UK projects, including the Severn Trent Birmingham Resilience Programme and the United Utilities Oswestry Water Treatment Works, where we’ve adapted international lessons for the UK context.

The importance of resilience was reinforced in early 2025 when the Environment Agency reported the UK’s driest start to spring in 69 years. Richard Thompson, Deputy Director of Water, emphasised the need to prepare for drought, an urgency now shaping planning and investment across the sector.

With competitive tenders underway for the design, build, financing and operation of assets, authorities are seeking delivery partners with geographic reach and a mobile workforce. While GHD is still relatively new to the UK market, our ability to draw on a global pool of knowledge and adapt it locally gives us a recognised role in meeting current water security goals.

After decades of inertia, the UK is entering a new phase of water infrastructure investment. The scale is significant, the timelines are tight and the challenges are complex. Yet with regulatory support, financial commitment and public backing, the sector is better equipped to move forward.

Key takeaways for industry stakeholders:

• Reservoirs and water transfer schemes will be essential to addressing projected water-supply gaps.
• Environmental considerations, from wetland creation to reduced abstraction, are now important in gaining approvals and community support.
• Agile delivery partners with proven experience in large-scale infrastructure are instrumental in maintaining momentum.

The Havant Thicket Reservoir illustrates how technical delivery, environmental care and community engagement can be aligned. As more projects move from planning to construction, the UK water industry has an opportunity to build long-term resilience for generations to come.

About GHD

GHD is a leading professional services company operating in the global markets of water, energy and resources, environment, property and buildings, and transportation. Committed to a vision to make water, energy, and communities sustainable for generations to come, GHD delivers advisory, digital, engineering, architecture, environmental and construction solutions to public and private sector clients. Established in 1928 and privately owned by its people, GHD’s network of 12,000+ professionals is connected across 165 offices located on five continents.