Research and analysis

Thames water situation: February 2025 summary

Updated 12 March 2025

Applies to England

• Publication for Northern Ireland
• Publication for Scotland
• Publication for Wales

1. Summary

Thames area received 62mm of rainfall through February, 130% of the long term average (LTA). River flows increased at only one of our key indicator sites in comparison with last month. Seven of our areal rainfall units were above normal, 4 sites were normal and the remaining 4 sites had notably high rainfall throughout the month. Groundwater levels declined at 6 of our indicator sites in February. Ampney Crucis, Fringford and Jackaments Bottom, all located in the Oolitic aquifer all decreased from the previous month’s levels. The Lower Thames and Farmoor reservoirs both decreased during February to end the month below the average for the time of year. There were 35 fluvial flood alerts, and 2 flood warnings issued in Thames Area in February.

2. Rainfall

Thames area received 62mm of rainfall through February, 130% of the long term average (LTA). The majority of areal units received normal rainfall, while in the west of Thames area, Berkshire Downs and Enbourne received above normal precipitation. Nearly half the month’s rainfall fell over four days (9, 21, 23, 26 of February), with a quarter of the month’s rainfall (16mm) falling on 23 January. In the past 6 to 12 months across most of Thames area we have had exceptionally high rainfall.

3. Soil moisture deficit and recharge

Soil moisture deficits (SMD) increased slightly from January at 2mm across Thames area however this is still below the LTA of 4mm. Effective rainfall for February was 139% of the LTA, and over the winter period so far (October to February) 185% of LTA effective rainfall occurred.

4. River flows

Monthly mean flow increased at just one of our key indicator sites compared to last month. Marlborough (above normal) was the only site that measured a monthly mean flow increase on last month. The remaining 14 indicator sites showed a decrease in monthly mean flow. Across the total number of indicator sites, 7 were above normal, 4 were normal and the remaining 4 sites were notably high in February. Bourne End Hedsor recorded its fifth highest February flow since records began in 1965.

5. Groundwater levels

Groundwater levels decreased at 6 of our indicator sites in February. Ampney Crucis, Fringford and Jackaments Bottom, our 3 Oolite sites, all decreased from the previous month’s levels. Nonetheless many boreholes record higher levels; The Flashes, in the Lower Greensands, alongside Ampney Crucis and Stonor Estate in the Chalk measured as exceptionally high. Marcham in the Corallian, Gibbet Cottage in the Chalk and Frith Cottage in the Lower Greensands are measured as notably high.

6. Reservoir stocks

Reservoir stocks rose in the Lower Thames reservoirs and ended the month at 88.2%, compared to 91.5% at the end of January. Stocks in Farmoor reservoir decreased from 96.3% to 93.1% during February. The Lower Thames reservoirs and Farmoor ended the month below average for the time of year.

7. Environmental impact 

During February there were 35 fluvial flood alerts, and two flood warnings issued in Thames Area. At the end of the month, no abstraction licences were being constrained in the area to protect water resources and the environment.

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.