Research and analysis

Thames water situation report: July 2024 summary

Updated 14 August 2024

Applies to England

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

1. Summary

Thames area received 77mm of rainfall in July, 158% of the long term average (LTA). Most areal units in the east received above normal rainfall and those in the west received normal rainfall. Soil moisture deficits (SMD) increased from last month to 82mm across the area, and ended the month close to the LTA (81mm). Monthly mean river flows at all our indicator sites were notably high or above normal, except the River Wye at Bourne End (exceptionally high), and the River Coln at Bibury (normal). At the end of the month, most of our groundwater sites’ levels continued their expected seasonal decline. The groundwater levels at all our sites were normal or above for the time of year.

2. Rainfall

July was wetter than typical, with Thames area receiving 77mm of rainfall during the month, 158% of the LTA. Most of the rain fell in the first week of the month with 5 July receiving 26mm. There was a largely east-west distribution to the rainfall across the area, with mainly above normal rainfall in the east and normal rainfall in the west. Rainfall for the last 3 months was normal, however due to the wet winter, rainfall continued to be exceptionally high for the last 6 and 12 months.

3. Soil moisture deficit and recharge

Drier than normal soils in June were wetted by July’s rainfall and the SMD ended the month at 82mm, close to the LTA (81mm). SMDs were similar throughout the area, however the Cotswolds East and Cotswold West units in the northwest of the area were slightly lower. Increased seasonal evaporation, and the presence of the SMD, meant that effective rainfall for the month was low (3mm).

4. River flows

With July’s higher than average rainfall, and despite June’s lower than average rainfall, monthly mean flows at most of our indicator sites were notably high or above normal, though nearly all sites continued their usual seasonal decrease. Many of the groundwater fed rivers (River Blackwater, River Wey, River Wye) were still supported by the continued contribution of groundwater baseflow resulting from the exceptionally wet winter. Sites on less permeable clay geologies (River Cherwell, River Ock) reacted quickly to the high rainfall in early July due to high run off rates.

5. Groundwater levels 

Almost all the groundwater sites continued their expected seasonal declines, though the levels remained normal or above for the time of year following the exceptionally wet winter. The Chalk aquifer at Stonor Estate and the Corallian at Marcham were both exceptionally high for July. The Inferior Oolite aquifer at Jackaments Bottom was the only site that was at a normal level. Groundwater levels of the Lower Greensand (both Folkestone and Hythe) remained notably high for the sixth month in a row.

6. Reservoir stocks

Reservoir capacity at Farmoor was steady, starting the month at 98% and ending the month at 99%; above the LTA. Capacity at the Lower Thames reservoirs decreased from 95% in June to 90% at the end of July but remained above the LTA for the time of year.

7. Environmental impact 

There were 3 flood alerts issued across Thames area during July. At the end of July, 19 abstraction licences were being constrained in Thames 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