The challenge of building more reservoirs to ensure UK’s water resilience

A new potable water reservoir hasn’t opened in the UK since 1992, when Severn Trent Water’s Carsington Reservoir in Derbyshire was completed. Portsmouth Water is currently building a reservoir in Havant, which is expected to open in 2029, while Anglian Water is pushing through plans for two more reservoirs, though they won’t be online until 2035 in a best-case scenario.

A drought was declared this week in the south-west of England and it is likely that this will become a common scenario around the country in the coming years. The National Infrastructure Commission (NIC) has calculated that there could be a capacity gap in the UK of up to 4bn litres per day by 2050. The country needs to build its water resilience, and reservoirs are the main method.

There is a seemingly direct link between the 1989 privatisation of water companies in the UK and the ceasing of new reservoirs being built. While there have been a number of flood alleviation reservoirs built by the Environment Agency in this time, the water companies have not invested in potable drinking reservoirs.

Speaking to NCE, ICE Reservoirs Committee chair Richard Coackley says that this is because the private companies are looking to “maximise all of the assets that have been built by the Victorians and the generations since”.

They’ve been averse to investing in new reservoirs because they are such big projects. “New reservoirs are expensive; they take a long time to construct and particularly to get through planning and environmental applications,” Coackley says. “Unless there’s been a drought recently, people say ‘Well, why do we need a new reservoir?’”

Coackley believes that water companies have been allowed to focus on other projects because Ofwat has been regulating with a light touch. “This has meant that the water companies have tried to take off the low-hanging fruit, which is actually just maximising the assets they’ve already got,” he says.

While the older infrastructure has “held up beautifully”, it might be overwhelmed by the challenge of climate change. “It’s a really important aspect to realise that the climate change that we see now may actually change the yield of those existing reservoirs,” Coackley explains. “Therefore, we may need to consider how we can raise some of our existing dams to increase water capacity and water storage.”

More desirable are brand new dams and reservoirs that are resilient against climate change, but Coackley believes the way the water sector is managed makes this difficult. “The big challenge we’ve got is we’ve not got a unitary view across flooding, water storage and drinking,” he says. “Remember that the Victorians didn’t just create these reservoirs for drinking water, what they did is create these reservoirs as part of the municipal benefit for society and all of these valleys. What they were doing was reducing the flooding when the floods came through, storing the floodwater and drinking that later on.”

The fracturing of the water industry into private entities makes this holistic planning difficult, Coackley says. “We now have the Environment Agency building flood alleviation reservoirs upstream of towns and cities to stop the flooding, but then they aren’t used for drinking water,” he says. “It needs leadership and it needs a unified overview of the whole aspect of the water cycle. We should be thinking of the much bigger picture in the UK, of what’s the unified process.”

He continues: “It’s short sighted. We don’t have a leader looking after all the aspects, [someone] with their neck on the block if there’s a potential disaster. It needs real leadership to be shown across all of [the water companies]; they all need to come together and show that unified leadership.”

While the recent move towards building new reservoirs is encouraging for Coackley, it is just the start. The need for new reservoirs is rapidly growing.

NIC assistant director Ed Beard tells NCE: “As the population has grown, the climate has changed and we have recognised the need to better protect the environment, a widening gap has opened between the water available and the water we need for public supplies.

“We fear there’s a one in four risk of severe drought across much of England in the next 30 years unless action is taken. The Commission has calculated the overall capacity gap could be as much as 4bn litres a day by 2050. New storage and transfer systems have a key role to play meeting that gap alongside water efficiency and reducing leaks.”

According to Beard, NIC has calculated that there will need to be £20bn invested into new supply infrastructure and tackling leakages by 2050 to help address the 4bn litre capacity gap.

One of the biggest issues is the length of time it takes to get a reservoir scheme going. The environmental implications of a new reservoir are far-ranging. Geotechnical investigations must be carried out, environmental impact mitigations must be devised and detailed.

Gaining planning approval also depends on local councils and, despite reservoirs being of benefit to the public, locals are not often keen to have their environment dug up. This can slow down the planning process to get everyone onside, especially if they see the short-term negatives far more clearly than the long-term benefits.

“They are huge civil engineering projects,” Beard says. “Fundamentally you are digging a huge hole in the ground, or blocking up a valley. There is no getting around the fact that you are using a large expanse of land and the construction work will inevitably be disruptive and costly.

“And there is the added challenge of the fact that, in many cases, it will not necessarily be the local population who will directly benefit from the additional supply.”

Even after final planning permission has been granted, the NIC says it takes about a decade on average to build the reservoir. There is also a need for panel engineers to oversee the design and construction, and their numbers have dwindled while there have been no new dams and reservoirs constructed.

This is all the more reason to start working on them now. “As we face greater weather extremes, we need to get moving on this new infrastructure to avoid even greater strains on water supply networks in the future,” Beard says. “As challenging as they can be as projects, there are few things as important to us as a secure water supply.”

He adds that a number of water companies are currently working on plans for approval by the regulator in the next price review period, while the government has announced plans to streamline the process for major water infrastructure projects.

“The key thing is that we don’t allow our recent dry summer to become a memory and for the importance of boosting water supply capacity to drop down the agenda,” he says.

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