Research and analysis

South London groundwater situation: 16 December 2024

Updated 20 December 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

In October 2024, the Chalk aquifer in South London area started to see some early signs of recharge due to an exceptionally wet September. In November, however, levels started to fall once again as the rainfall received was closer to normal during most of October and November.

After a couple of weeks of intense rainfall received in the first 2 weeks of December, groundwater levels have now started to rise sharply. This demonstrates that the recharge season has now started in South London.

Groundwater levels are notably high for this time of the year in South London. This is due to a previous wet recharge season, the early recharge seen in October and the current sharp rise of groundwater levels.

Short term forecast 

Although groundwater levels are notably high for this time of the year, they are likely to increase further. Weather forecasts for the next one or 2 weeks predict conditions that are likely to be settled with intermittent spells of rain.

Longer term forecast 

Trends of groundwater levels are dependent on the amount and intensity of rainfall we receive in South London until the end of the groundwater recharge season. The recharge season typically comes to an end in the spring. 

For the next 3 to 4 weeks, conditions are forecast to be changeable, with some unsettled, wet spells predicted to be possible. If we receive higher than average rainfall in the next month, groundwater flooding of basements and low-lying land could be possible in February and March. This would also result in winter bournes (rivers which flow in winter because of high groundwater levels) such as the Caterham Bourne beginning to flow.

Graph showing the trend of groundwater levels since February 2023 at Woldingham Observation Borehole in South London overlying a background of colour banding indicating relatively high and low conditions. Levels are notably high for this time of the year on 16 December 2024.

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 this winter. The next report will be published in January unless the situation changes significantly. 

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 next month unless there are any significant changes.

Further information

You can view:

Contacts

If you have any questions, please email [email protected].

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

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