Letter to Steve Reed MP, Secretary of State for Environment, Food and Rural Affairs regarding the Proposed Abingdon Reservoir (SESRO)

26 March 2025

The Rt Hon Steve Reed MP

House of Commons, London,

SW1A 0AA

Dear Steve Reed,

Proposed Abingdon Reservoir (SESRO)

I am writing on behalf of Abingdon Carbon Cutters, our local community action group, with regards to the proposed reservoir development,

We are very worried about the reservoir in terms of its huge size – if built it would be the largest bunded (above- ground) reservoir in Europe – its huge carbon footprint and the potential for significant contribution to the serious flooding that we have experienced in South Abingdon in recent years due to climate change. Storms are becoming larger and more intense.

The reservoir would have 25-metre-high sides covering 7 square miles of flat, flood-prone land with a water table currently only 2 feet below the surface of the land. It would completely dominate the landscape and be very close to surrounding villages.

^{Gard Ariel Montage}

Any wall breach in the reservoir would devastate the surrounding villages and South Abingdon and any detected weakening in the wall would mean prolonged evacuation of the surrounding villages and towns.

We have compiled a list of good reasons why the reservoir should not be built and suggested some solid alternatives, which we hope you will consider:

Reasons why a reservoir near Abingdon (SESRO) is not suitable:

• The reservoir would raise the water table by 1 metre on land where the water table is already very close to the surface. In a meeting with OCC at County Hall in February 2024, the hydrologist consultant, from the firm Mott Macdonalds working for Thames Water at the time, said the effects are significant around the ‘south and east side’ of the reservoir – East Hanney, Steventon and South Drayton were mentioned. As at March 2025, the 11 metre long, 2.5 metre high, trial site for the Abingdon Reservoir is water-logged and behind schedule. They are having to pump water off the site and extend working hours. The trial does not represent the 25 metre wall-height of a proposed 150Mm³ reservoir.

^{Trial reservoir site}

• A yet-to-be-designed groundwater drain around the reservoir bund – will be aimed at conducting the groundwater more quickly to the River Ock. This means that the Ock levels will rise faster in heavy rain, as the flow will arrive faster at the reservoir’s northern end, and hence to the Ock. This will result in greater flooding issues in South Abingdon – houses were flooded 3 times in 2024.

• To protect South Abingdon from increased flooding, a form of flood mitigation would be of benefit eg by creation of a wetland west of Abingdon, in the same area as the proposed reservoir, to divert flood water from the River Ock .
• Reservoirs of the type that exists in N Wales, Lake District, Scotland, the Pennines, at Kielder Reservoir in Northumberland and Rutland Water are made by damming rivers from wetter, mountainous, westerly areas. The water can be piped downhill to rivers elsewhere in the country.  The SESRO reservoir proposed by Thames Water is a huge clay tub, which would have to be filled by pumping water uphill out of the Thames – a stretch of river suffering from raw sewage pollution, especially when there is prolonged rain. Water will only be available for filling the reservoir when flows in the Thames at Days Weir are above 1450 Ml/d, in order to protect downstream water supplies. This means that, in the major 18-month droughts for which the reservoir is designed, there is virtually no water available for refilling the reservoir. In effect, the reservoir is a giant water tank – when it’s empty, the supply stops, even if the drought continues for longer. There is no resilience to longer droughts, eg three dry summers and two dry winters.

• The carbon footprint of building the reservoir will have the largest construction carbon footprint of any strategic water project at 410,000 CO₂e.

• A SESRO-sized resource is not needed because the government has forced the Water Companies to aim for Leakage Reduction and Personal consumption targets. Australian personal consumption is approx. 80 litres per person per day, Uk consumption is 142 litres.  German and Danish water pipe leakage rates are 1/4 of Thames Water’s rates.

• Thames Water has a colossal £19 billion debt, caused by investors and directors borrowing money and then siphoning money off for themselves. 33p in every £1 paid by Thames Water customers goes to service this debt. Entrusting Thames Water with another £7.6 billion – OFWAT estimate- for the reservoir will undoubtedly result in more money going to shareholders and directors.

Alternatives to SESRO:

• Thames water has another water resources solution: transfer of water from the River Severn to the Thames; water transfer from the wetter, mountainous, west is embodied by the Severn Thames Transfer, which would be more flexible and adaptable to build than SESRO. National water resource studies in the 1970s and 1990s recommended that the STT should be the next major water resource scheme. This option would be deliverable in 5 years.

• More than half the supposed need for water, equivalent to five SESROs, is for replacing existing supplies deemed by the Environment Agency to impact river ecology, termed “environmental destination”. We support reductions in abstraction from iconic chalk streams that have been severely affected by over-abstraction, particularly in the Chilterns and the River Darent in Kent. However, much of the reduction in supplies is in the lower reaches of rivers like the River Lea in East London and River Colne to the North of Heathrow, where the river channels are heavily modified and ecology is not dependent on river flows. Source: John Lawson https://www.newcivilengineer.com/opinion/thames-waters-abingdon-reservoir-why-a-public-inquiry-is-needed-immediately-15-01-2025/

• Proceed with the planned 100 Ml/d Grand Union Canal transfer to north London areas. There may be enough water to supply both Affinity Water and Thames Water.

https://www.ofwat.gov.uk/wp-content/uploads/2021/12/Standard-gate-one-final-decision-for-Grand-Union-Canal-Transfer.pdf

Storage of water in underground aquifers: this is the best form of underground storage and is used in the North London Aquifer Recharge Scheme, where water is pumped from the aquifers beneath North London, and supplied by pipeline to the Lee Valley Reservoirs. This has a supply capability of nearly 50% of SESRO, and the aquifer is recharged via treated water from the London works. Another aquifer scheme is the West Berkshire Groundwater Scheme (WBGWS), capable of supplying about 1/3 of the supply of SESRO in a drought. There is potential for more use of aquifers in the north of the country, which would enable more water from the north-west to be transferred to the south.

https://www.bgs.ac.uk/geology-projects/groundwater-research/groundwater-resources-in-the-uk/

• A local solution (just an idea at the moment, I’m not aware of any feasibility studies) would be to provide all households in London, containing a garden, with rainwater storage tanks – they can be sited under the garden. This water, although not chemically treated, is suitable for watering gardens, flushing downstairs toilets and for use in washing machines. In 2023, London had 3.8 million homes.  Four fifths of these homes have a garden. https://www.london.gov.uk/sites/default/files/2024-11/London%27s%20Housing%20Stock%20-%20Research%20Unit%20-%20November%202024.pdf This plan would be independent of Thames Water, reducing people’s water bills and enabling them to hold on to more of their wages. The widespread introduction of smart meters, already being implemented by the government, will encourage home water collection in addition to more careful home water management.

There is significant local opposition to the reservoir on many different ecological and practical grounds – safety, efficacy, carbon footprint, flooding risk, cost and more.

I hope that you will carefully consider the points above.

Your sincerely

Caroline Townsend

Chair, Abingdon Carbon Cutters

• A local solution (just an idea at the moment, I’m not aware of any feasibility studies) would be to provide all households in London, containing a garden, with rainwater storage tanks – they can be sited under the garden. This water, although not chemically treated, is suitable for watering gardens, flushing downstairs toilets and for use in washing machines. In 2023, London had 3.8 million homes.  Four fifths of these homes have a garden. https://www.london.gov.uk/sites/default/files/2024-11/London%27s%20Housing%20Stock%20-%20Research%20Unit%20-%20November%202024.pdf This plan would be independent of Thames Water, reducing people’s water bills and enabling them to hold on to more of their wages. The widespread introduction of smart meters, already being implemented by the government, will encourage home water collection in addition to more careful home water management.

There is significant local opposition to the reservoir on many different ecological and practical grounds – safety, efficacy, carbon footprint, flooding risk, cost and more.

I hope that you will carefully consider the points above.

Your sincerely

Caroline Townsend

Chair, Abingdon Carbon Cutters

I would like to acknowledge the help and advice from Derek Stork, Chair of GARD, in researching this issue.