Research and analysis

Kent and South London water situation: October 2024 summary

Updated 13 November 2024

Applies to England

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

The whole of the Kent and South London (KSL) area received 117% of the long term average (LTA) rainfall during October. Rainfall received across all catchments was normal for this time of year. In general, soil moisture deficits (SMDs) decreased throughout all rainfall areas during October, however some rainfall areas that had soil that was close to being fully saturated at the end of September saw a marginal increase. Monthly mean flows ranged from normal to notably high in October. Groundwater levels during October continued to fall across most of the KSL area and ranged from normal to notably high for this time of the year. Levels at the end of the month at the 5 water company reservoirs in the area ranged from normal to exceptionally high. Levels at most of the reservoirs increased throughout October, and levels at the other reservoirs either slightly decreased or remained stable.

1. Rainfall

The whole of the KSL area received 117% of the LTA rainfall during October. Rainfall received across all catchments was normal for this time of year. The percentage of LTA rainfall received across catchments ranged from 89% in the Darent rainfall area to 131% in the North Kent Chalk rainfall area. The highest daily rainfall total of 35.5 mm for October was recorded at Cranbrook sewage treatment works (STW) rain gauge in the Medway catchment on the 8 September. The second to fifth highest daily rainfall totals were on 13, 16, 07 and 20 September and ranged from 28mm to 15.9mm across the North Downs to South London, Stour and Dover Chalk catchments. The driest day was 5 October, with only 0.3mm of rain recorded across the whole area. 

The whole KSL area recorded the fifth wettest 12 months ending in October on record since records began in 1871. The Medway catchment saw the second wettest 12 months on record. The Dover Chalk and Eastern Rother rainfall areas recorded the third wettest 12 months.  

2. Soil moisture deficit and recharge

At the end of October, SMDs were, on average, 30mm. SMDs tend to be higher than this at this time of year, in line with the expected end of October LTA, which is 73mm. In general, SMDs decreased throughout all rainfall areas during October, however some rainfall areas that had soil that was close to being fully saturated at the end of September saw a marginal increase. SMDs in the south and west of the patch ranged from less than 10mm to 40mm. SMDs in the north and east of the patch were higher and ranged from 41mm to 130mm. SMDs decreased in most catchments to the East in October, attributed to the ongoing effective rainfall which stood at 154% of the LTA

3. River flows

Monthly mean flows (MMFs) ranged from normal to notably high in October. Eight out of the eleven key flow sites saw notably high MMFs, and all of these are located near the centre and in the east of the patch. Two key flow sites located in the west of the area observed above normal MMFs, and the remaining key flow site, also located in the west of the area, saw normal MMFs. The highest MMF was recorded at the Rother at Udiam, which saw 266% of the LTA for the month of October. The lowest MMF, which was 75% of the LTA, was observed at the Ravensbourne at Catford.

4. Groundwater levels   

In general, groundwater levels continued to fall across the KSL area. This is with the exception of Riverhead and Fleet Reservoir, where the groundwater levels have stabilised in October. In general, the slowdown or discontinuation of the fall of groundwater levels is consistent with the continued pattern of effective rainfall that in October was 158% of the LTA.

At the end of October, groundwater levels across the whole KSL area ranged from normal to notably high. The Lower Greensand aquifer at Riverhead continued to observe groundwater levels that are notably high for this time of year, with a slight rise continuing this month. Groundwater levels in the Chalk aquifer were also mostly notably high. The exception are the key monitoring points in the west of the patch registering levels in the Chalk at Chipstead and Sweeps Lane that are assessed as normal and above normal, respectively. 

5. Reservoir stocks

At the end of October, levels at the water company reservoirs in KSL ranged from normal to exceptionally high. Levels at 3 of the 5 reservoirs in the area increased throughout October, these were:

• Powdermill
• Darwell
• Bough Beech

Levels at Powdermill and Bough Beech reservoirs were above normal, at 88% and 73% respectively. Levels at Darwell, which had a live capacity of 80% on day 31 of the month, were notably high. In comparison, levels at Bewl reservoir, which had a live capacity of 63% at the end of October, decreased slightly during the month. Levels at this reservoir were normal for this time of year.  Weirwood remained offline during October, and the levels at the reservoir, which were exceptionally high for this time of year at 100% live capacity, stayed stable.

6. Environmental impact 

Thirty-two fluvial flood alerts were issued from 6 to 17 October.

Author: Groundwater and Hydrology Team, ksl.gwh@environment-agency.gov.uk

Contact Details: 03708 506 506

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.