Research and analysis

Thames water situation: January 2026 summary

Updated 17 February 2026

Applies to England

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

1. Summary

Thames area received 137mm of rainfall in January, which was the wettest January since 2014. The majority of areal rainfall units were exceptionally high, Loddon, Lower Wey, and Wey Greensand, had over double the long term average (LTA) rainfall. Soil moisture deficits (SMDs) were negligible in all areal units by the end of the month. Saturated soils allowed significant effective rainfall to occur, with 202% of the LTA. The majority of monthly mean river flow sites were normal for the time of year, however 4 were exceptionally high. Groundwater levels increased at all of our indicator sites in January. Four sites, Ampney Crucis (great oolite), Long Sutton (chalk), and Frith Cottage, and The Flashes, both in the lower greensand, were exceptionally high. Both Farmoor reservoir and the Lower Thames reservoirs were below average for the time of year.

2. Rainfall

Thames area received 137mm of rainfall in January which was 183% of the LTA, the wettest January since 2014. Exceptionally high rainfall fell across the majority of Thames area, with only Thame, Cotswolds West, and Upper Thames receiving notably high status. Three rainfall units in the south of Thames area, Loddon, Lower Wey, and Wey Greensand, had over double the LTA rainfall. Three days (8, 15, 26 January) accounted for just over a third of the month’s rain. While Rapsgate raingauge (Cotswolds West) had the highest daily total, receiving 33.9mm of rainfall on 15 January.

3. Soil moisture deficit and recharge

High rainfall throughout the month saturated soils and caused SMDs to reduce. SMDs were negligible in all areal units by the end of the month which meant they were wetter than usual. Saturated soils allowed significant effective rainfall to occur, 202% of the LTA at the end of the month.

4. River flows

Monthly mean river flows increased at 8 of our indicator sites in January. The majority of sites are normal for the time of year, however, 2 were above normal, 1 was notably high, and 4 were exceptionally high (Cherwell at Banbury, Blackwater at Swallowfield, Wey at Weybridge, and Wey at Tilford). The river Cherwell at Banbury recorded it’s third highest January flow since 1967, the Blackwater at Swallowfield recorded it’s third highest since 1953, and the Wey at Tilford recorded it’s second highest since 1955.

5. Groundwater levels   

Groundwater levels increased at all of our indicator sites in January in response to the above average recharge. Four sites, Ampney Crucis (great oolite), Long Sutton (chalk), and Frith Cottage, and The Flashes, both in the Lower Greensand, were exceptionally high. Fringford (great oolite) was notably high, while, Marcham (Corallian), Rockley (chalk), and Model Farm (upper greensand) were above normal. All others were normal.

6. Reservoir stocks

Reservoir stocks in Farmoor decreased from 97.2% to 80.4%, while the Lower Thames reservoirs increased from 85.4% to 88.6%. Both Farmoor reservoir and the Lower Thames reservoirs were below average for the time of year.

7. Environmental impact 

During January 70 fluvial and one groundwater flood alerts, and 3 flood warnings, were issued on rivers in the Thames area. At the end of January, no abstraction licences were being 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.