Thames water situation: April 2026 summary
Updated 13 May 2026
Applies to England
© Crown copyright 2026
This publication is licensed under the terms of the Open Government Licence v3.0 except where otherwise stated. To view this licence, visit nationalarchives.gov.uk/doc/open-government-licence/version/3 or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: psi@nationalarchives.gov.uk.
Where we have identified any third party copyright information you will need to obtain permission from the copyright holders concerned.
This publication is available at https://www.gov.uk/government/publications/water-situation-local-area-reports/thames-water-situation-april-2026-summary
1. Summary
Thames area received 11mm of rainfall in April, just 20% of the long term average (LTA) and the 10th driest April on record. Soil moisture deficits (SMD) increased to 69mm, compared to the LTA of 28mm. Effective rainfall was negligible across Thames area. River flows are being sustained by high winter rainfall, however a third of indicator sites were below normal. Groundwater levels decreased at all sites, which is to be expected, the majority were normal for the time of year. Farmoor reservoir was above average while the Lower Thames reservoirs were below average for the time of year. In April, 1 groundwater flood alert remained in place.
2. Rainfall
Thames area received 11mm of rainfall in April, which was 20% of the LTA. All areal rainfall units recorded notably low levels of rainfall, apart from Thame, which was exceptionally low. There were a total of 13 dry days in April, and only 2, 12 and 15 April, that had over 2mm of rain. It was the 10th driest April on record.
3. Soil moisture deficit and recharge
For the second month in a row, drier weather has increased SMD across Thames area and ended the month on 69mm, which is higher than the LTA of 28mm. There was also negligible effective rainfall.
4. River flows
Monthly mean flows decreased at all our indicator sites. Two-thirds of our sites were normal for the time of year, however, one-third, were below normal. The Thames at Kingston was below normal with 58% of its LTA flow. River flows are being supported due to exceptionally high rainfall over winter, however the current dry weather has started to reduce flows.
5. Groundwater levels
At the end of the month, groundwater levels declined at all of our indicator sites, which is to be expected as the annual recharge season has ended and the annual recession is taking place across the area. The majority of indicator sites are normal for the time of year. Jackaments Bottom in the Inferior Oolite recorded notably low. This aquifer has low storage capacity and high permeability which cause water levels to fall rapidly during periods of low rainfall. Gibbet Cottages (Berkshire Downs Chalk) was above normal. The Flashes in the Lower Greensand (Folkestone) was notably high, having declined gradually from exceptionally high levels at the end of March. Levels in the Lower Greensand (Folkestone) typically decline slowly as the aquifer has high storage capacity.
6. Reservoir stocks
Reservoir stocks in Farmoor again decreased slightly from 98.6% to 98.1%, while the Lower Thames reservoirs decreased from 93% to 92.8%. Farmoor reservoir was above average while the Lower Thames reservoirs were below average for the time of year.
7. Environmental impact
In April there was 1 groundwater flood alert remaining in Thames area. At the end of April, 3 abstraction licences were constrained in the area to protect water resources.
Author: Thames Area Groundwater Resources and Hydrology, enquiriesWT@environment-agency.gov.uk
Contact Details: 030708 506 506
All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Environment Agency. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use of the information, or reliance upon views contained in this report.