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Thames Water accelerates plans to secure South East's future water supply

  • Thames Water accelerates plans to secure South East's future water supply
  • The reservoir will secure the future water supply of 15 million people across the South East, supplying Thames Water, Southern Water and Affinity Water customers.   

  • The UK has not built a new reservoir for over 30 years and Thames Water forecasts that across London and the Thames Valley it will need an extra 1 billion litres of water every day by 2050 to protect against the effects of climate change and population growth. 

  • It’s estimated that a severe drought could cost London’s economy alone as much as £500 million a day.

About the entity

Thames Water
Every day, we serve 15 million customers across London and the Thames Valley.


Thames Water has launched a public consultation on its proposals for a new reservoir near Abingdon in Oxfordshire, a nationally significant infrastructure project that is vital to securing the South East’s future water supply.

A significant amount of design and development work has taken place since the autumn 2023 proposals were shared with local communities. As a result, Thames Water is unveiling a new interim masterplan and design concepts. Together, they show how the reservoir could look, how it might be built, and how it may benefit visitors, becoming so much more than a place to store water, with vast blue and green spaces for leisure and recreation.

Proposals for the reservoir, known as SESRO (South East Strategic Reservoir Option), have been developed in conjunction with Southern Water and Affinity Water, as the reservoir is designed to secure future water supplies for all three company’s customers, a projected 15 million people –including customers in Oxfordshire.

Investing in the construction of a new large-scale 150Mm3 reservoir would ensure there is enough water to meet the needs of a growing population into the next century and beyond, while simultaneously protecting against the effects of climate change. More than 19 million people currently live in the South and East of England, and this is forecast to grow by 2 million across London and the Thames Valley by 2050.

Leonie Dubois, Thames Water’s Head of Engagement, Land and Consents said: “Our water resources are under threat, and the consequences of not investing in a new reservoir could be to the detriment of millions of people, the environment, and the economy, so it’s vital we take action. Investing in SESRO would provide a drought insurance policy for households and businesses right across the South East.

“We have a unique opportunity ahead of us to address the water shortage risk, whilst seizing the chance to create a new, much-loved community resource with leisure, employment and recreational benefits for those that live nearby."

The National Infrastructure Commission (NIC) has also stated that around nine nationally significant water resource projects are needed before 2030 to prepare for anticipated water scarcity, with the findings set out in its second National Infrastructure Assessment. If the Oxfordshire reservoir is given the green light by the Government it is expected to take at least 15 years to complete, with a target opening date of 2040.

With the reservoir supplying people living far beyond the Oxfordshire border, Thames Water is encouraging individuals and communities across the South East to have their say and to respond to the public consultation

With the reservoir supplying people living far beyond the Oxfordshire border, Thames Water is encouraging individuals and communities across the South East to have their say and to respond to the public consultation. In addition to assuring water supplies, the reservoir will also help to improve the environment by reducing abstractions from rivers and groundwater sources, including Hampshire’s rare and sensitive chalk streams, the Test and Itchen.

The interim masterplan for SESRO is separated into seven different zones, which the public are asked to comment on. This includes information about the opportunities for leisure, which could include nature trails, a visitor centre, cafés, a water sports centre, recreational lakes and an education centre.

Feedback is also sought on potential changes to the local road network as part of wider plans to better connect communities to the reservoir and each other. New public rights of way (PROWs) and an enhanced road network would help to ensure that residents in the nearby villages of East Hanney, Steventon, Drayton, Marcham and Garford could all access the new open spaces with ease.

Lee Dance, Organisational Director at Water Resources South East, said: “It’s important that we make the right decisions for the whole of the region. SESRO is a critical part of the forward-looking programme of investment in our water supplies, set out in WRSE’s regional plan, which will provide water to people across the South East.  

“It will provide a new strategic water resource, producing up to 270 million litres of water per day that will be moved across the region, providing additional water supplies to 15 million people.  

“It’s critical we have the right infrastructure in place to meet the challenges ahead, including climate change and population growth, and to help us leave more water in our rivers and streams to help protect our region’s environment.”  

The SESRO public consultation will be supported by a series of community events which will help visitors to contextualise the visual layout proposed for the reservoir. This will include a new virtual reality headset experience, which enables people to view the reservoir from different vantage points, 3D models and new computed generated images.  

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