Research and analysis

Wessex water situation: November 2024 summary

Updated 13 December 2024

Applies to England

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

1. Summary

November marked a continuation of the wet weather from the previous 2 months with an average of 115mm of rainfall across Wessex, 137% of the long term average (LTA). Almost all of the rain and snow in November fell during the latter half of the month, particularly between 23 and 24 November during Storm Bert. Soil moisture deficit (SMD) initially increased during November in response to the drier start to the month before decreasing towards zero at the end of November. Monthly mean flows recorded across Wessex were all notably high or above normal apart from the River Washford at Beggearn Huish which reported normal flows. By the end of November, daily mean flows were falling at every site following the peak caused by Storm Bert. Groundwater sites towards the south of Wessex reported notably high levels at the end November while sites in the north reported exceptionally high levels. Reservoirs ended the month at around 99% and 91% capacity for Wessex Water and Bristol Water respectively. For Wessex Water this was similar to levels this time last year. For Bristol Water, levels were slightly lower than in November 2023.

2. Rainfall

In November an average of 115mm (137% LTA) of rain fell across Wessex. Most hydrological areas received normal rainfall while 6 areas in the northeast received above normal rainfall. In all hydrological areas in Wessex, rainfall during November was above average. Over 96% of November’s rain fell during the latter half of the month with 47% of the monthly total falling on the weekend of 23 and 24 November during Storm Bert.

Nine of the past 12 months have received above average rainfall and it has been the wettest 10 and 11 month periods to November since our records began in 1871. This year is therefore on course to be the wettest calendar year since records began. In the last 3 months, most hydrological areas received exceptionally high rainfall with notably high levels recorded in a few areas to the south and west. In the last 6 months, areas largely received above normal rainfall to the west and notably high rainfall to the east of Wessex. All areas of Wessex received exceptionally rainfall over the last 12 months.

3. Soil moisture

Soil moisture deficit (SMD) in Wessex initially increased from around 1mm to around 6mm during the first couple of weeks of November. In response to rainfall during the latter half of November, SMD decreased to near zero on average across all areas of Wessex at the end of the month. The SMD at the end of November was slightly lower than the LTA deficit across most of Wessex but overall was similar to November last year.

4. River flows

All reporting sites across Wessex recorded notably high or above normal mean flows in November, apart from the River Washford at Beggearn Huish which recorded normal monthly mean flows. All sites recorded their peak flows for November following the high rainfall during Storm Bert.

By the end of the month, daily mean flows were falling across every site following the peak caused by high rainfall during Storm Bert. Sites in Chalk catchments largely ended November with notably or exceptionally high flows as they are supplemented by water from the Chalk aquifer. Most catchments with other underlying geologies ended the month with above normal flows.

5. Groundwater levels   

All groundwater monitoring sites across Wessex ended November reporting either notably or exceptionally high levels. All sites showed slightly increased levels compared to the end of October. All sites to the south of Wessex including those monitoring the Chalk reported notably high levels at the end of the month. The two sites which recorded exceptionally high levels at the end of November were Allington and Didmarton to the north of Wessex (monitoring the Great and Inferior Oolite formations respectively). At the end of the month, all sites except Over Compton (monitoring the Bridport Sands formation) showed slightly increasing levels.

6. Reservoir stocks

Both Wessex Water and Bristol Water reservoir levels initially decreased in November before rising sharply in response to the rainfall during the latter half of the month. Wessex Water reservoirs ended the month around 99% capacity while Bristol Water reservoirs ended November around 91% capacity. The current combined levels for Wessex Water are similar to those recorded this time last year while for Bristol Water they are slightly lower than in November 2023. For both Wessex Water and Bristol Water, levels are significantly higher than in November 1995.

Author: Wessex Hydrology, [email protected]

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.