Affinity Water provides on average 950 million litres of water each day to a population of more than 3.6 million people across the south east of England. But the UK’s largest, water-only supplier must significantly increase its future supply if future demand is to be met . They must do this whilst considering the role that demand management and the further reduction of leakage will play.
A key issue is protection of the environment and, in particular, ‘chalk streams’ – rivers fed by water from underground chalk aquifers and springs. Currently, Affinity Water gets its water from the natural environment with 65% coming from groundwater and 35% from surface water. Voluntary reduction in existing sources are being implemented to help preserve these delicate river ecosystems that support a wealth of wildlife.
WSP is carrying out a feasibility study to consider how the Grand Union Canal (GUC), England’s longest canal structure that dates to the early nineteenth century, could offer an alternative, resilient water resource for Affinity Water. Our aim is to help the utility plan how to provide a reliable, efficient and affordable water supply to customers, through to 2080 and beyond, while minimising environmental impacts.
Exploiting existing resources to boost water supply resilience
The proposal we are exploring with Affinity Water would see the GUC transfer highly treated wastewater from Minworth Sewage Treatment Works (managed by Severn Trent Water) in the Midlands to Affinity Water in Hertfordshire and North west London (Affinity’s Central Region). This transfer could provide peak additional flows of between 50 and 100 million litres of water per day to Affinity Water customers.
Making use of recovered wastewater in this way creates an extremely resilient and reliable water resource because even in times of severe drought there will be ‘recovery’ water available. Importantly, having an import like the GUC transfer would also support the voluntary sustainability reductions at existing groundwater sources, leaving more water available to support natural river flow and lakes, and ease pressure on valuable chalk streams.
Resilient water sources for Affinity Water are vital given that climate change is likely to reduce the supply of water in its area by 39 million litres of water per day by 2080. The South East of England is already classified as a severely water stressed area. For example, between July 2016 and April 2017 the area received 33% less rainfall than the national average. Yet population growth in this same area is set to reach 51% by 2080, that is equivalent to approximately 1.8 million more people.
The Grand Union Canal transfer proposal in the regional context
The proposal for the GUC transfer is one of being considered by Affinity Water in partnership with Severn Trent Water, the Canal and Rivers Trust, Thames Water and Anglian Water. There are 17 options in total across the industry.
Each strategic option is one of six long-term strategic options being developed so that they can be compared on the basis of costs, carbon, sustainability, resilience, and environmental benefit/costs. The aim of creating ‘competing’ schemes is to deliver the best social, environmental and economic outcomes for the region and communities these water providers serve. The schemes also require the different water suppliers to collaborate, creating water supply solutions that traverse different regions.
