Research and analysis

Wessex water situation: May 2026 summary

Updated 11 June 2026

Applies to England

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

The dry weather continued in May 2026, with an average of 38mm of rain falling across Wessex, 64% of the long term average (LTA). The majority of the month was dry with the largest rainfall event occurring on 18 May. Across the whole of Wessex, the last 4 months have been the seventh driest for this period on record, with it being the third driest of these 4 months on record for the Yeo and Kenn, and Little Avon catchments.

Soil moisture deficit (SMD) rose through May in response to the low rainfall and ended the month at similar levels to 2025. Monthly mean flows continued to fall through out May, with a temporary response to rainfall around 18 May in surface water dominated catchments. Flows were predominantly notably low and below normal in the north of Wessex, with normal flows to the south-west of the patch and below normal and notably low flows to the east of Wessex. Groundwater levels continued to fall across Wessex in May. At the end of the month, most sites reported normal levels across Wessex, with 4 sites below normal, and one site, Didmarton 1 (monitoring the Inferior Oolite), recording above normal groundwater levels. At the end of May reservoir levels for Wessex Water and Bristol Water were at approximately 83% and 86% capacity respectively.

1. Rainfall

An average of 38mm of rain fell across Wessex in May, 64% of the LTA. The month started and ended with very dry conditions, with 95% of the total monthly rain falling from 11 to 20 May, with the largest rainfall event occurring on 18 May. From north-east to south-east of Wessex rainfall was below normal, with the exception of The Upper Hampshire Avon catchment which was notably low. In the north-west and west of Wessex rainfall was predominantly normal across the hydrological areas.

The highest total monthly rainfall was recorded in the Little Avon catchment with an average of 54mm, 87% LTA. The lowest total monthly rainfall was reported in the Upper Hampshire Avon catchment with 23mm, 43% LTA.

Across the whole of Wessex, the last 4-month period (February to May) has been the seventh driest on record. It has also been the third driest 4-month period on record for both the Yeo and Kenn catchment and the Little Avon catchment. With the continuation of dry weather through May, the last 3 months shows most hydrological areas with notably low rainfall with exceptionally low rainfall to the south-east of Wessex. In the past 6 months, after a wet winter, the hydrological areas to the south west show exceptionally high rainfall, with notably high rainfall recorded across Wessex, with the north and north west having above normal levels of rainfall. The last 12 months show above normal levels of rainfall to the south with notably high rainfall to the south west. In the north of Wessex, the majority of hydrological sites recorded normal amounts of rainfall. 

2. Soil moisture

SMD continued to rise across Wessex for the majority of May, nearing the historic maximum in mid-May, and ending the month close to 2025 levels, before beginning to decrease into the next month. By the end of the month all hydrological areas across Wessex, bar one, had SMD levels between 71mm to 100mm, the exception being the River Bourne catchment in the east of Wessex where there were higher levels of SMD between 101mm to 130mm. SMD by the end of the month was 26mm to 50mm greater than the LTA for all hydrological areas.

3. River flows

River flows continued to fall in May across the majority of Wessex in response to the continuing dry weather. Most reporting sites in the north recorded notably low monthly mean flows, with the Bristol Frome at Frenchay reporting an increase in flows to below normal.

In the south of Wessex normal monthly mean flows were reported at 3 sites, with the Dorset Frome at East Stoke Combined reporting below normal flows, and notably low monthly mean flows on the Stour at both Throop and Hammoon. 

River flows across the Chalk aquifer in the east of Wessex reported as below normal, with monthly mean flows in the west of Wessex reporting as mainly notably low, with below normal flows on the Washford at Beggearn Huish and normal flows on the Isle at Ashford Mill.

While all catchments showed a falling river flow trend throughout the month, surface water catchments showed a temporary response to a rainfall event around 18 May.

4. Groundwater levels   

Groundwater levels continued to fall across all of Wessex in May due to the continuation of dry weather. By the end of the month, the majority of monitoring sites across Wessex reported normal groundwater levels. Of the 4 monitoring sites reporting below normal levels, 2 of these were at sites monitoring the Chalk aquifer towards the east of Wessex, Oakley Industrial Estate and Woodyates. The remaining 2 sites reporting below normal levels were to the west and north of Wessex at Chipley (monitoring the Otter Sandstone) and Wrington (monitoring the Carboniferous Limestone). In the north of Wessex, one site reported above normal levels at Didmarton 1 (monitoring the Inferior Oolite) falling from notably high groundwater levels at the end of April. Monitoring sites in the south of Wessex reported normal levels on the Chalk aquifer.

5. Reservoir stocks

Reservoir levels have fallen through May for both Bristol Water and Wessex Water. Wessex Water ended the month at approximately 83% capacity, similar to 2025 and higher than 1995. Bristol Water ended the month at approximately 86% capacity, higher than in 2025 and similar to 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.