Research and analysis

Wessex water situation: July 2025 summary

Updated 12 August 2025

Applies to England

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

1. Summary

July was the fifth consecutive dry month in Wessex. An average of 30mm of rain, 50% of the long term average (LTA) fell across Wessex. When considered alongside the preceding 4 months, this has been the second driest 5 month period (March to July) since records began in 1871. Soil moisture deficit (SMD) initially increased in July before briefly falling following a period of rainfall in the middle of the month. By the end of July, SMD was rising again and was close to the historic maximum. Monthly mean flows recorded across Wessex in July were largely below normal or notably low. Daily mean flows in July largely peaked around 20 July following rain on 19 July. The majority of groundwater sites, including most sites monitoring the Chalk aquifer, reported below normal or notably low levels at the end of July. The exceptions were Didmarton and Overcompton which both recorded normal levels and Oakley Industrial Estate which recorded exceptionally low levels. Overall reservoir levels for Wessex Water were approximately 57% capacity at the end of July while for Bristol Water, levels were approximately 52% capacity.

2. Rainfall

An average of 30mm of rain fell across Wessex in July (50% of the LTA). This is the fifth consecutive dry month, resulting in the second driest 5 month period (March to July) since records began in 1871 and the driest since 1976. Most rain in July occurred on a few days in the middle and towards the end of the month. The highest average daily rainfall across Wessex was on 19 July which accounted for 25% of the total rain for the month. The lowest relative rainfall was recorded in Poole Harbour (39% of the LTA). The highest relative monthly rainfall was recorded in the Little Avon (71% of the LTA). In July, almost all hydrological areas in Wessex received below normal rainfall overall.

Over the past 3 months, the majority of hydrological areas in Wessex received notably low rainfall. The exceptions were 3 areas to the south which received below normal rainfall. Over the past 6 months, the majority of areas in the north of Wessex received exceptionally low rainfall while the majority of areas in the south of Wessex received notably low rainfall. Over the past 12 months, all hydrological areas in Wessex have received normal rainfall.

3. Soil moisture

SMD in Wessex initially continued to increase for the first week of July. Following rain in the middle of July, SMD decreased briefly but was rising again by the end of the month. Throughout July, SMD remained relatively close to the historic maximum for this time of year. Across most hydrological areas in the north and west of Wessex, SMD was in the range of 101mm to 130mm at the end of July. In most hydrological areas in the south of Wessex, SMD was between 131 and 160mm. For most areas of Wessex, SMD at the end of July was between 26mm and 50mm greater than the LTA. For the lower Hampshire Avon and Poole Harbour and Purbeck in the south of Wessex however, SMD was between 51mm to 75mm greater than the LTA at the end of July.

4. River flows

In July, most flow sites in Wessex received either below normal or notably low monthly mean flows. There were 3 sites in the south and west of Wessex which recorded normal monthly mean flows in July and 3 sites in the north and west of Wessex which recorded exceptionally low monthly mean flows. Most sites monitoring flows on or downstream of the Chalk aquifer recorded either below normal or notably low flows. Relative monthly mean flows were slightly higher across most sites in the south of Wessex on the Chalk aquifer as flows were supported by baseflow from the aquifer. Daily mean flows at most flow sites peaked around 20 July following the rain on 19 July.

5. Groundwater levels   

Following 5 consecutive dry months, the majority of groundwater sites in Wessex, including most sites monitoring the Chalk aquifer, ended July reporting either below normal or notably low levels. Oakley Industrial Estate (monitoring the Chalk) and Chipley (monitoring the Sandstone) were the only sites to report exceptionally low levels at the end of the month. For all monitoring sites, groundwater levels decreased throughout the month.

6. Reservoir stocks

Both Wessex Water and Bristol Water reservoir levels continued to decrease throughout July. The combined levels at the end of the month for Wessex Water were approximately 57% capacity while for Bristol Water, combined levels were approximately 52% capacity. For both water companies this is notably lower than reservoir levels recorded this time last year. For Wessex Water, reservoir levels at the end of July were similar to this time of year in 1995 while for Bristol Water, levels were lower than the end of July 1995.

Author: Wessex Hydrology, hydrology.wessex@environment-agency.gov.uk

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.