Research and analysis

Wessex water situation: October 2024 summary

Updated 13 November 2024

Applies to England

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

1. Summary

After the record breaking rainfall in the previous month, the wet weather continued into October with an average of 132mm of rainfall across Wessex, 158% of the long term average (LTA). There was rain through most of the month but 6 to 8 and 13 to 18 October were particularly wet periods. Soil moisture deficit (SMD) started the month around 10mm and gradually decreased towards zero at the end of the month. Monthly mean river flows across Wessex were all exceptionally high apart from the River Washford at Beggearn Huish which reported notably high flows. Eleven sites recorded their highest monthly mean flows for October on record. By the end of October daily mean flows were reducing across most reporting sites in Wessex, although sites in Chalk catchments remained notably or exceptionally high. All groundwater reporting sites across Wessex reported exceptionally high levels at the end of the month. Groundwater levels were shown to be decreasing for all reporting sites monitoring the Chalk aquifer bar the two most northern slower responding sites on the aquifer. Five sites recorded their highest levels on record for the end of October. Reservoirs were at around 95% and 82% capacity for Wessex Water and Bristol Water respectively, slightly higher than the levels seen this time last year.

2. Rainfall

In October an average of 132mm (158% LTA) of rain fell across Wessex. In general, hydrological areas in the east received normal rainfall and those in the west received above normal rainfall, although it was well above average for all areas. There were 2 periods of higher rainfall with 34% of the monthly total falling from 6 to 8 and 43% falling between 13 and 18 October. There was very little rainfall across Wessex from 20 October through to the end of the month. Nine out the past 12 months have received above average rainfall and it has been the wettest 9, 10 and 11 month periods to October since our records began in 1871.

Over the longer term, in the last 3 months hydrological areas received either notably high or exceptionally high levels of rainfall. In the last 6 months areas predominantly received notably high levels of rainfall with exceptionally high levels recorded in the south, whereas the last 12 month period is still recording as exceptionally high across all of Wessex.

3. Soil moisture

The soil moisture deficit (SMD) gradually decreased throughout the month from around 10mm on average to near zero on average across Wessex. The SMD at the end of October was significantly lower than the long term average (LTA) but similar to the SMD at this time last year.

4. River flows

All reporting sites across Wessex reported exceptionally high monthly mean flows in October, apart from one, the River Washford at Beggearn Huish, which recorded notably high monthly mean flows. Eleven of our 20 reporting sites recorded their highest monthly mean flows for October on record. This included sites in the Bristol Avon, Hampshire Avon, Stour and Dorset Frome catchments.

By the end of the month the daily mean flows were dropping across every site in response to the lack of rainfall towards the end of October. Sites in Chalk catchments ended the month with notably or exceptionally high flows as they are supplemented by water flowing from the aquifer. Most of the catchments with other geologies ended the month with normal flows.

5. Groundwater levels   

All groundwater monitoring sites across Wessex ended October reporting exceptionally high levels. All sites showed increased levels from the previous month, in response to the record breaking rainfall from September.

By the end of the month al sites monitoring the Chalk showed decreasing levels, apart from the 2 most northerly sites reporting on the Chalk, Tilshead and Chitterne Down which reported slightly increasing levels. Didmarton (monitoring the Bridport Sands formation) and Chitterne Down, Oakley Industrial Estate, Delcombe and Kingston Russell Road (all monitoring the Chalk) recorded their highest levels on record for the end of October.

6. Reservoir stocks

Wessex Water reservoirs increased throughout October and ended the month around 95% full, with Bristol Water reservoirs also increasing throughout the month ending at around 82% capacity. The current combined levels are slightly higher than those recorded at this time last year for both Bristol Water and Wessex Water, and they are both significantly higher than the levels seen in October 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.