Research and analysis

South London groundwater situation: February 2026

Updated 25 February 2026

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

Current situation

In January 2026, the Chalk aquifer in the South London area started to experience groundwater recharge after receiving 194% of the monthly long-term average rainfall for January. This caused groundwater levels to rise sharply from early January to mid February, and they are expected to continue rising for the rest of the month.

Short term forecast

Although groundwater levels are normal for this time of year, they are likely to increase further. Weather forecasts for the next one to two weeks predict unsettled conditions, with frequent light to moderate rain with prolonged dry spells unlikely.

Longer term forecast

Groundwater level trends are dependent on the amount and intensity of rainfall received in South London until the end of the groundwater recharge season. The recharge season typically ends in spring.

For the next 3 to 4 weeks, conditions are forecast to be changeable with unsettled and rainy spells likely. If above-average rainfall continues, groundwater flooding of basements and low-lying land could occur; however, at present this is unlikely. Above-average rainfall could also result in winter bournes (rivers that flow in winter because of high groundwater levels), such as the Caterham Bourne, beginning to flow.

Graph showing the trend of groundwater levels since May 2024 at the Woldingham Observation Borehole in South London overlying a background of colour banding indicating relatively high and low conditions. Levels are normal for this time of year as of 20 February 2026.

What the Environment Agency is doing

We will continue to monitor groundwater levels across South London and provide situation report updates throughout the remainder of the winter. The next report will be published next month unless the situation changes significantly. 

We will take evidence-based decisions and 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 provide a further update next month unless there are any significant changes. 

Further information

You can view:

Contacts

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

The Environment Agency offers free groundwater flood alerts. You can:

  • call Floodline on 0345 988 1188 to register for the service
  • follow @EnvAgencySE and #floodaware on X/ Twitter for the latest flood outlook
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