| Europe
Left: Carsington Water in Derbyshire was the last major public water supply reservoir to be constructed in the UK for water supply purposes in 1991. New reservoirs are now urgently needed
Coire Glas, BDS provided project updates on some of these schemes at one of its recent seminars. Portsmouth Water’s Ruari Maybank is the Project
Director for the Havant Thicket Reservoir which is described as an environmentally led project that won’t address the challenges of population growth or the impact of climate change, but will protect globally rare chalk streams in Hampshire. In 2017 Southern Water agreed to reduce abstraction
from these chalk streams by up to 18Megalitres a day through addressing customer consumption and leakage in pipes, but realised that it still required more sustainable sources to protect such rare habitats. “And this where Portsmouth Water comes in,” Maybank explained. “As we are lucky enough to manage the largest freshwater springs network in Europe which is used to provide drinking water.” Havant Thicket Reservoir provides an opportunity to
capture surplus water which would otherwise travel a short distance out to sea, and capture and store it until needed in times of drought or emergency. After considering 70 different locations the chosen one was considered ideal due to its close proximity to the freshwater spring, meaning building pipe infrastructure and pumping water up to the reservoir would be cheaper. Fewer trees on the site also meant it had a lower environmental impact and favourable geographical considerations included its location in a shallow valley rich in London clay. This can be used to build the embankment and reduce project costs, and minimise its construction carbon footprint with less vehicles to disrupt local roads and communities. Maybank said that the project is about more than
the reservoir itself as 12km of pipes, pumping stations and a new pipe network need to be constructed to help transfer treated water towards an existing service reservoir, to enable the release of water from their network to Southern Water’s to supply their customers. Planning permission for Havant Thicket was
received in 2020. From 2023-6 clay will be dug out and the reservoir built. It is hoped that by 2029 the reservoir will be filled with water. Key lessons that Portsmouth Water have learned
from this project include: It’s never too early to appoint construction engineer. Market engagement needs to be included in the reference design. Projects are delivered by people and not contracts or agreements and so stakeholder engagement is absolutely crucial.
Start environmental compensation early. Portsmouth Water started in 2019 and planted over 6000 trees and created wildlife corridors. This was done before planning permission was secured, not as it had to be done but as felt like right thing to do. This gave the new habitat a chance to mature and provide a home for wild life affected by construction when it started.
Maybank added that the company is mindful this is the first of several reservoirs to be built in the region and they are keen to learn from the wider professional community and share lessons learned. With this in mind, it has signed a memorandum of understanding with the University of Portsmouth to provide a learning legacy. Mark Malcolm, Programme Director for major infrastructure at Anglian Water, also spoke about plans for two new raw water reservoirs in East England, similar in size to Grafham Water which has an area of 6.3km2
of 57Mm3
, maximum depth of 21m and maximum volume .
He described the new reservoirs as significant assets of about 50Mm3
that will not just water supply but also
support the farming industry and become a catalyst for growth in the East of England. The Fens Reservoir will take about five to seven
years to construct, with water supply anticipated by 2035-7, and the Lincolnshire Reservoir will take six to eight years with water supply by 2039-41. Factors driving the need for reservoirs in the East
of England include the fact that this unique low-lying region is one of driest in the UK, with a third less rainfall than the country average, plus one of fastest growing parts of the country with 20% population growth predicted by 2050. So, in the face of climate change, water supplies need to be protected. While Georgina Seely, Head of Strategic Resources Engineering at Thames Water spoke about plans for a new reservoir in Oxfordshire. Several options are currently being looked at and the largest one will be 150Mm3
consisting of a traditional embankment design, about 15-20m high with a maximum water depth of
33m.It is hoped that planning consent will be granted by 2030 and water should be available by 2040. For the first ten years 30% of the water will be for Affinity customers, 30% Southern Water and 40% Thames Water customers. Seely said that as the project develops Thames
Water hopes it will enhance the environment and become an asset to be proud of in the future.
References
Could the UK benefit from a water strategy? Institution of Civil Engineers Presidential Roundtable summary June 2023.
https://www.ice.org.uk/ media/3zhkvi3b/pres-rt- write-up-water-strategy- presidential-roundtable-june- 2023-v2.pdf
BDS seminar on new UK dams. 24 April 2023.
www.ice.org.uk/events/ past-events-and-recordings/ recorded-lectures/bds-agm- new-dams-lecture-2023
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