Policy paper

Thames groundwater situation: 29 April 2025

Updated 30 April 2025

Applies to England

© Crown copyright 2025

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This publication is available at https://www.gov.uk/government/publications/thames-west-area-groundwater-situation/thames-groundwater-situation-4-march-2025

Current situation

Groundwater levels are currently dropping following recent settled weather across the Thames catchment. A groundwater flood alert is in force at Henley and Assendon in Oxfordshire. A further 5 locations are at levels that require awareness. 

Groundwater levels at Great Shefford, West and East Ilsley, Compton, Chilton and West Hagbourne have fallen further, and our alerts have been removed.

The levels in the Lambourn Valley, Leckhampstead (West Berks) and Piddington (Bucks) are at levels that require awareness.

This briefing note provides an update on the levels at these 6 locations. It also includes links to a range of websites containing further information. Levels at our Farringdon Borehole in Alton, Hampshire, have fallen below the awareness level.

Henley and Assendon

Groundwater levels at our Stonor observation borehole have fallen slightly. However, groundwater remains at a level where communities may be impacted. A groundwater flood alert was issued for this area on 21 January 2025. This will remain in force over the coming weeks as levels are expected to remain high.

Great Shefford

Groundwater levels at the Northfield Farm observation borehole in the Great Shefford area continue to fall. The groundwater flood alert was removed on 29 April 2025, as we expect the declining trend to continue into the summer season.

West and East Ilsley, Compton, Chilton and West Hagbourne

Groundwater levels at our Hodcott observation borehole near West and East Ilsley have fallen recently. The groundwater flood alert was removed from this area on 29 April 2025, as we expect the declining trend to continue into the summer season.

Piddington

Groundwater levels at the Piddington observation borehole near West Wycombe and High Wycombe, Buckinghamshire, continue to fall slowly. With the current declining trend, we do not expect to issue a groundwater alert. We will continue to monitor closely, and we may consider removing this notification over the coming weeks.

Lambourn Valley

Groundwater levels at the Longacre observation borehole in the Lambourn Valley are falling steadily. The groundwater flood alert was removed for this area on 8 April 2025. We will continue to monitor closely, and we may consider removing this notification over the coming weeks.

Leckhampstead

Groundwater levels at our Chapel Wood observation borehole continue to fall.  The groundwater flood alert was removed on 8 April 2025. We will continue to monitor closely, and we may consider removing this notification over the coming weeks.

Summary of other groundwater sites

Levels at all our groundwater sites are dropping following recent dry weather. We continue to monitor groundwater levels and will update this briefing note and remove flood alerts as and when appropriate.

Forecast risk of flooding

The Met Office monthly weather forecast indicates that May should start dry with more changeable conditions later in the month.

The Met Office forecast is regularly updated.  

More details can also be found in the monthly Water Situation Report for England.

Actions and advice

To find out if you can register to receive free flood alerts for flooding from groundwater:

You can monitor daily groundwater levels on the check for flooding website for:

You can view historic levels for our sites on the Hydrology Data Explorer. This includes Draycot Foliat.

Following the flooding last winter, the Environment Agency reduced the level at which we think impacts are likely to 86.2 mAOD. This is not yet reflected on the GOV.UK Check for Flooding website which shows the higher action level of 89.15 mAOD.

Find information on river, sea, groundwater and rainfall levels on GOV.UK.

You should also:

  • review your individual and community group flood plans
  • check pumps and any other flood protection equipment you have
  • keep drains and gullies around your property free of debris
  • prepare to move valuables from basements and cellars

Next update

Flood risk increases with the continuing rising groundwater. We will update this briefing note weekly for as long as one or more sites exceed the notification levels. We will also issue updates if the situation changes significantly.

Further information

Find more information on groundwater levels and the water situation report.

You can also get practical advice on what to do before, during and after groundwater flooding on the check for flooding website.

Check the 5-day flood risk.

Contacts

For more information on the flood alert service and to find out what messages you are registered to receive, call Floodline on 0345 988 118.

Alternatively, you can contact the Environment Agency for more information:

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