Europe | “The scale of the challenge in the UK cannot be
underestimated,” Shaw said. “We currently require 15,000Ml/day for the population. By 2055 this is expected to grow by an additional 5000Ml/day.” With last major water storage reservoir built in early 1990s, this means that even the newest supply dams in the UK are at least 35 years old. “The majority of these are critical to our water supply needs but even with all existing reservoirs functioning there’s still a substantial shortfall in storage in UK,” Shaw warned. “As these reservoirs age, maintenance becomes more onerous. At some point these dams will reach the end of their serviceable life and will need either removing or replacement or significant capital investment to upgrade them.”
Driving construction Supply side solutions to this shortfall include a portfolio of
Above: Llyn Vyrnwy Dam in Wales
Below: Water overflowing Derwent Dam into Ladybower reservoir, in Derbyshire. UK
are too small for safe access, leading to maintenance with associated high costs whenever any work is necessary.
Looking to the future Human induced climate change is very apparent, the
Chair of the British Dam Society said. He gave the recent example of drought in UK when the summer of 2022 was driest since July 1935. There were restrictions in water supply and stress on the supply network, especially across southern parts of the country, with scientists saying it provided a warning for future years. With the above in mind, a number of policies and
strategies have recently been developed by the government and other bodies to more effectively manage water resources across the country. Key objectives are: ● Improving drought resilience. ● Reducing consumption. ● Reducing leakage in water networks. ● Developing more supply side capacity in the system. ● Ambitious long term environmental enhancement. This includes protection of chalk streams which are particularly vulnerable to drier weather. 85% of the 200 chalk streams globally are in southern and eastern England and are an important haven for wildlife too.
28 schemes which include ten new reservoirs proposed for completion by 2059, providing more than 300Mm3 storage and 670Ml/day. The largest of these are off-river reservoirs filled by using excess water during winter. Shaw said that pumped storage, and a critical need
to store more renewable energy to stabilise the electric grid, is also helping to drive reservoir construction in the UK is. A large number of new pumped storage schemes are under consideration and, if all implemented, would provide an additional 12GW of capacity – a fourfold addition to existing pumped storage hydropower capacity. The majority of these are in Scotland. Flood protection is also said to be influencing
reservoir construction. With climate change bringing more frequent and intense storms, areas previously not subjected to flooding could become inundated, Shaw warned. While other areas with defences are slowly seeing a reduction in the level of protection such defences are offering. Coupled with growing population and the sprawl of urban areas, it will place a greater number of people and properties at risk from flooding. Although the UK has been building flood storage
reservoirs for decades, Shaw said that the climate changes we’re witnessing means existing water supply reservoirs may need to be adapted to build in freeboard extra capacity, so they can manage floods as well as provide water supply.
Further complications Climate change is further complicating matters as some
80% of UK dams are earthfill embankments. Warmer weather and prolonged droughts are resulting in low water levels for extended periods, and can lead to drying and cracking in back dam fill materials, making them more prone to leaks and other durability issues. While more intense and frequent storms means that overflows and spillways, when combined with the height of the dam, may not have adequate capacity to safely pass the extreme storm event without risking the integrity of the dam. This can lead to major remedial works across the country in order to raise dams and increase spillway capacity. In addition, increasing population density downstream of reservoirs also increase the threat posed by dam failure.
References
https://www.ice.org.uk/events/recorded-lectures/ice-and- colegio-de-ingenieros-de-caminos-canales-y-puertos- ciccp-bilateral-summit December 2025
20 | May 2026 |
www.waterpowermagazine.com
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