Wessex water situation: March 2025 summary
Updated 14 April 2025
Applies to England
© Crown copyright 2025
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1. Summary
In March there was very little rainfall across Wessex, resulting in the driest March since 1961 and the driest overall month since May 2020. An average of 8mm, 11% of the long term average (LTA) fell across Wessex. Despite this, over the past 6 months all hydrological areas have received normal rainfall and over the past 12 months most hydrological areas in Wessex have received either above normal or notably high rainfall. Soil moisture deficit (SMD) increased throughout March with all hydrological areas reporting between 11mm and 40mm at the end of the month. The majority of monthly mean flows across the north and west of Wessex were below normal. The majority of sites to the south of Wessex reported either normal or above normal monthly mean flows. Most groundwater sites monitoring the Chalk reported normal levels at the end of March while Didmarton in the north of Wessex monitoring the inferior Oolite recorded notably high levels. Reservoirs ended March at approximately 96% capacity on average for both Wessex Water and Bristol Water.
2. Rainfall
An average of 8mm of rain fell across Wessex in March (11% of the LTA). The lowest relative rainfall was recorded in the Wylye and Nadder (7% of the LTA) while the highest was recorded in the Axe and the Yeo and Kenn (19% of the LTA). Only 3 days during March recorded an average of over 1mm of rain across Wessex. The wettest day of the month was 21 March when an average of 4mm fell (43% of rain during March). All hydrological areas across Wessex received exceptionally low rainfall during March. Overall, this has been the fourth driest March since records began in 1871 and the driest March since 1961. It has also been the driest month since May 2020.
Over the past 3 months, the West Somerset Streams was the only hydrological area to receive below normal rainfall, with all other areas receiving normal rainfall. Over the past 6 months, all areas received normal rainfall. Over the past 12 months, most hydrological areas received either above normal or notably high rainfall due to high rainfall over the last year. The West Somerset Streams and the Tone in the west of Wessex were the only areas which received normal rainfall over the past 12 months.
3. Soil moisture
SMD in Wessex increased throughout March. At the end of the month, all hydrological areas in Wessex recorded a SMD in the range of 11mm to 40mm. The majority of Wessex recorded a SMD between 26mm to 50mm greater than the LTA at the end of March. In the few remaining hydrological areas mainly to the south east of Wessex, SMD at the end of March was between 6mm and 25mm greater than the LTA. At the end of March, SMD in Wessex was the highest on record for this time of year.
4. River flows
In March, the majority of flow sites to the north and west of Wessex reported below normal monthly mean flows. The 2 exceptions were Frenchay (monitoring the Bristol Frome) which recorded notably low flows and Fenny Castle (monitoring the Sheppey) which recorded normal mean monthly flows. All sites monitoring flows on and downstream of the Chalk aquifer recorded either normal or above normal monthly mean flows in March as the flows are supported by strong baseflow from the Chalk aquifer. Across all flow sites in Wessex, daily mean flows fell throughout most of March except for a small peak in flows following the rain on 21 March. All flow sites ended March with lower flows than they had at the start of the month.
5. Groundwater levels
The majority of groundwater monitoring sites across the south of Wessex, including sites monitoring the Chalk aquifer ended March reporting normal levels. The only exception was Tilshead (monitoring the Chalk) which recorded above normal levels. In the north of Wessex, Didmarton (monitoring the inferior Oolite) recorded notably high levels at the end of March. For most of the month, groundwater levels across all sites were decreasing in response to the very limited rainfall.
6. Reservoir stocks
Reservoir levels began to decrease during March for both Wessex Water and Bristol Water. The current combined levels for both Wessex Water and Bristol Water are approximately 96% capacity. This is lower than Wessex Water reservoir levels recorded this time last year but slightly higher than those recorded by Bristol Water in March 2024. For both Wessex Water and Bristol Water, reservoir levels recorded at the end of the month are slightly lower than the end of March 1995.
Author: Wessex Hydrology, hydrologywessex@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.