Thames water situation: July 2026 summary
Updated 12 August 2026
Applies to England
© Crown copyright 2026
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This publication is available at https://www.gov.uk/government/publications/water-situation-local-area-reports/thames-water-situation-july-2026-summary
1. Summary
It was the driest July for Thames area since records began in 1871. Thames area received just 1mm of rainfall in July, around 1% of the long term average (LTA). The Environment Agency declared drought status for Thames area during July. The end of month soil moisture deficits (SMDs) were much higher than expected for the time of year. Monthly mean flows decreased at all river indicator sites in Thames area. One-third of these sites were notably low, while a further third were exceptionally low. Groundwater levels continued their seasonal decline, with levels across Thames area ranging from notably low to notably high at the end of July.
2. Rainfall
It was the driest July for Thames area since records began in 1871. Just 1mm of rainfall was recorded in July, around 1% of the LTA, and rainfall was exceptionally low across all hydrological areas. July 1885 was the second driest on record, with 6.6mm of rainfall, followed by July 2022 as the third driest, with 7.3mm. Two hydrological areas, Upper Thames and Lower Wey, received less than 1mm of rainfall in July. The summer so far (April to July) has been the fourth driest on record, with just under half the expected rainfall. Only 1921, 1976 and 1990 were drier over the same period. For comparison, the drought year of 2022 ranked as only the eighth driest April to July period on record.
3. Soil moisture deficit and recharge
By the end of July, SMDs across most hydrological areas were significantly above the LTA, with the Cotswolds East and Cotswolds West hydrological areas exceeding twice their respective LTAs. Given the lack of rainfall, there was no effective rainfall across Thames area.
4. River flows
Monthly mean flows decreased at all indicator sites in Thames area. Five of our 15 indicator sites were notably low, while a further 5 were exceptionally low. The rivers with exceptionally low flows were the River Thame at Wheatley, the River Coln at Bibury, the River Kennet at Calcot, and the River Thames at Windsor and Kingston (naturalised). The River Ock at Abingdon was below normal, while the remaining 4 sites were normal for the time of year.
5. Groundwater levels
Groundwater levels continued their seasonal decline at all indicator sites in July. At the end of the month, 5 of our 11 indicator sites remained normal for the time of year. Groundwater levels in the chalk and Lower Greensand aquifers remained relatively resilient, due to storage of the high winter rainfall. Oolite aquifers were less resilient due to lower storage capacity. Levels at Jackaments Bottom (Inferior Oolite) remained notably low, while Rockley (Berkshire Downs Chalk) remained below normal. The Lower Greensand sites continued to have higher levels than typical for the time of year, with above normal levels at Frith Cottage and notably high levels at The Flashes. The only changes were at Ampney Crucis (Great Oolite) and Model Farm (Upper Greensand), where groundwater levels fell from normal at the end of June to below normal at the end of July.
6. Reservoir stocks
Farmoor Reservoir’s storage decreased to 91.8% at the end of the month, down from 98.9% at the end of June, and was below the LTA for the time of year. Storage in the Lower Thames Reservoirs also decreased, ending the month at 72.4%, down from 88.1% at the end of June, and was also below the LTA.
7. Environmental impact
At the end of July, 48 abstraction licences were having their flows constrained to protect 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 herein.