Research and analysis

South London groundwater situation: 21 May 2024

Updated 22 May 2024

Applies to England

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This publication is available at https://www.gov.uk/government/publications/mole-and-south-london-groundwater-situation/south-london-groundwater-situation-10-february-2020

Current situation

Across the South London area, groundwater levels began to rise suddenly in the early weeks of November. Levels typically begin to increase towards the end of November and early December. The sharp and early rise of groundwater levels was responsible for groundwater fluctuating between levels that are considered exceptionally high, notably high or above normal since November. 

Despite receiving above-average rainfall in April, groundwater levels gradually began to stabilise. Due to the drier weather and higher temperatures that we have been seen since the beginning of May, groundwater levels are now consistently falling.

Short term forecast  

For the next couple of weeks, higher temperatures and slightly above average rainfall is forecast across the south of the UK. However, conditions supporting recharge are much reduced with the increasing of temperatures and daylight hours.

Whilst groundwater levels are currently classified as Exceptionally High for this time of year, the effect of the end of recharge season is being reflected throughout the aquifers as levels begin to decline.

Longer term forecast  

If there is extremely heavy rainfall over the next few weeks, groundwater flooding of basements and low-lying land could still be possible. However, as groundwater levels are now falling, the likelihood groundwater flooding to occur is now decreasing steadily, until the start of the next recharge season. The Caterham Bourne flow is now falling and is anticipated to come to an end as we progress further into spring and towards summer. Bournes are rivers that flow in winter because of high groundwater levels.

Graph showing the trend of groundwater levels since August 2022 at Woldingham Observation Borehole in South London overlying a background of colour banding indicating relatively high and low conditions.

What the Environment Agency is doing  

We will continue to monitor groundwater levels across South London and provide situation report updates, if the outlook changes. If there is no change to the current outlook, indicating a low likelihood of groundwater flooding, the next report will be published after the onset of the next recharge season, which may be in late autumn 2024.

We will take evidence-based decisions. If conditions deteriorate, we will notify our partners (including lead local flood authorities and water companies). We will also actively engage with our partners to help them prepare for incident response.

Actions and advice

There is practical advice on what to do before, during and after groundwater flooding, and further guidance about groundwater flooding, how it might affect you and what to do.

Next update

We will continue to monitor groundwater levels closely and we will provide a further update at the beginning of the next recharge season later in the year unless there are any significant changes.

Further information

You can view:

Contacts

If you have any questions, please email enquiries@environment-agency.gov.uk.

The Environment Agency offers free Groundwater Flood Alerts. You can:

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