Thames water situation: June 2025 summary
Updated 15 July 2025
Applies to England
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1. Summary
Thames area received 33mm of rainfall in June, 63% of the of the long term average (LTA). All our areal rainfall units recorded below normal or normal rainfall, however over the last 3 months, rainfall in Thames area has been the seventh driest period since 1871, and the second driest recorded for Cotswolds West and Cherwell. Soil moisture deficits (SMD) increased significantly across Thames area, rising from 92mm in May to 124mm by the end of June. River flows decreased at all sites compared to last month, reacting to the sustained low rainfall over the last 3 months. Likewise, groundwater levels declined at the majority of indicator sites in June and ranged from exceptionally low (Inferior Oolite) to notably high (Chalk). The Lower Thames and Farmoor reservoirs ended the month slightly below the LTA.
2. Rainfall
Thames area received 33mm of rainfall in June, 63% of the LTA. All areal units received below normal or normal precipitation, the first time normal rainfall has been recorded since February. Rainfall over the last 3 months was exceptionally low across most of Thames Area. The last 3 months (April, May June) have been the 7th driest period for Thames area since 1871, and the 2nd driest recorded for Cotswolds West and Cherwell areal units.
3. Soil moisture deficit and recharge
SMD increased significantly across Thames area, rising from 92mm in May to 124mm by the end of June. This was significantly higher than the LTA of 67mm for the time of year, indicating that soils are much drier than usual. Cotswolds West, Chilterns West, Chilterns East and North Downs Hampshire all had their highest SMD’s since recordings began in 1920. The sharp increase reflected a sustained lack of effective rainfall; only 28% of the LTA occurred during June. This was due to a combination of sustained lower rainfall and increased sunshine hours
4. River flows
Monthly mean flows decreased at all key indicator sites compared to last month, largely due to dry soils and declining groundwater levels. The majority of sites recorded flows that were below normal or lower in June, with the River Coln at Bibury the only exceptionally low site. In contrast, Weybridge and Tilford on the River Wey had normal flow for the time of the year, buoyed by above normal groundwater levels higher in the catchment.
5. Groundwater levels
Groundwater levels decreased at the majority of our indicator sites in June and ranged from exceptionally low (Jackaments Bottom, Inferior Oolite) to notably high (Stonor Estate, Chalk). Groundwater levels of some sites changed banding in comparison with May, with Fringford (Great Oolite) and Rockley (Chalk) dropping from normal banding into below normal, and Gibbet cottages (Chalk) and Marcham (Corralian) dropping from above normal to normal. Overall, groundwater levels of the Chalk and Great Oolites remained normal or below normal, with the exception of Stonor Estate (Chalk). Levels of the slower responding Lower Greensands remained notably high for the time of year with Frith Cottage (Lower Greensand) remaining stable.
6. Reservoir stocks
Reservoir stocks decreased in the Lower Thames reservoirs and ended the month at 90.1%, compared to 93.6% at the end of May. Stocks in Farmoor reservoir decreased from 99.1% to 94.7% during June. The Lower Thames reservoirs and Farmoor reservoirs ended the month remaining below the LTA.
7. Environmental impact
At the end of the month, 34 abstraction licences were being constrained in the area to protect water resources and the environment. There were no flood alerts in force by the end of June.
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.