Wessex water situation: August 2024 summary
Updated 13 September 2024
Applies to England
© Crown copyright 2024
This publication is licensed under the terms of the Open Government Licence v3.0 except where otherwise stated. To view this licence, visit nationalarchives.gov.uk/doc/open-government-licence/version/3 or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: psi@nationalarchives.gov.uk.
Where we have identified any third party copyright information you will need to obtain permission from the copyright holders concerned.
This publication is available at https://www.gov.uk/government/publications/water-situation-local-area-reports/wessex-water-situation-august-2024-summary
1. Summary
August was a return to drier conditions following a wet July. An average of 44mm fell across Wessex equating to 67% of the long term average (LTA). Despite the lower rainfall in August, the past 12 month period (starting in September 2023) has been the second wettest since records began in 1871. Soil moisture deficit (SMD) continued to increase for most of August until the last week of the month when it began to decrease in response to a period of rainfall. The majority of monthly mean flows recorded in the north-west of Wessex were below normal, while flows in the south of Wessex were largely normal to above normal. Groundwater sites at the end of August were largely between normal and above normal. Throughout August, reservoir levels continued to decrease with Wessex Water ending the month at 63% capacity and Bristol Water ending August at 61% capacity.
2. Rainfall
An average of 44mm of rain fell across Wessex in August (67% of the LTA). Recorded monthly rainfall ranged from 21% to 92% of the August LTA. The lowest relative rainfall was recorded in the Tone and the highest recorded in Poole Harbour and Purbeck. Rainfall was concentrated on a few days, largely towards the end of the month. An average of 23mm fell between 22 August and 24 August (52% of rain during August). Hydrological areas across the north of Wessex received largely below normal rainfall and largely notably low rainfall in the west of Wessex. Across the south and east of Wessex, hydrological areas received normal amounts of rainfall. Over the past 3 months almost all of north Wessex received below normal rainfall and most of south Wessex received normal rainfall. Over the past 6 months, hydrological areas in the north of Wessex received normal to above normal rainfall and areas to the south received between above normal and exceptionally high rainfall. Over the past 12 months, almost all of Wessex received exceptionally high rainfall due to the wet winter and spring. This has been the second wettest 12-month period (September to August) since records began in 1871.
3. Soil moisture
SMD in Wessex continued to increase for the majority of August, before beginning to decrease towards the end of the month in response to rainfall. At the end of August, the majority of Wessex recorded a SMD in the range of 101mm to 130mm. Areas to the south and west of Wessex recorded a SMD in the range of 71mm to 100mm. The majority of Wessex had a SMD in the range of 6mm to 25mm greater than the LTA at the end of August.
4. River flows
In August, flow sites to the north west of Wessex largely reported below normal monthly mean flows with Frenchay (monitoring the Bristol Frome) recording notably low monthly mean flows. Sites across the northeast and south of Wessex largely reported between normal and above normal mean monthly flows with Baggs Mill (monitoring the Piddle) recording notably high flows. All sites monitoring flows on the Chalk aquifer except for Hammoon (monitoring the Dorset Stour) recorded mean monthly flows greater than the LTA. The majority of sites recorded flows peaking around 24 August following 3 days of high rainfall and flows in recession afterwards to the end of the month.
5. Groundwater levels
Groundwater levels at the end of August varied between normal and notably high across Wessex. Didmarton 1 (monitoring the Inferior Oolite formation) and Overcompton (monitoring the Bridport Sand formation) were the only sites to record notably high levels at the end of the month. Amongst the sites monitoring the Chalk aquifer, the 2 most southern sites Kingston Russell Road and Delcombe recorded above normal levels, whereas most of the northern sites monitoring the Chalk recorded normal levels at the end of August.
6. Reservoir stocks
Reservoir levels in Wessex continued to decrease throughout August. At the end of the month, Wessex Water reported reservoirs at approximately 63% capacity which is approximately 6% lower than this time last year. Bristol Water reported reservoir levels of approximately 61% capacity at the end of August which is approximately 16% lower than this time last year.
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.