Research and analysis

Kent and South London water situation: September 2026 summary

Updated 14 October 2026

Applies to England

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

1. Summary

Dry conditions persisted in September, with the Kent, South London and East Sussex (KSLES) area recording just 69% of the long term average (LTA) rainfall for the month. Soil moisture deficits (SMDs) continued to increase in response to limited effective rainfall, remaining significantly higher than the LTA and much higher than this time last year. River flows showed some recovery during September, with daily mean flows generally increasing across the area. However, monthly mean flows remained largely below usual for the time of year, ranging from notably low to normal. Groundwater levels continued to decline throughout September. Levels in the Chalk aquifer largely remained the same status as the end of August 2026, except at Chipstead which saw a sharp fall from below normal to exceptionally low. Levels in the Lower Greensand aquifer remained in the normal range. Four of the five reservoirs in the KSLES area recorded a decrease in storage during September; Bewl and Bough Beech remained below normal, while Weirwood fell into the normal range, and Darwell fell to notably low. Powdermill was the only reservoir to record an increase in levels, but only by 1%. However, all are tracking slightly steeper than normal drawdown rates. 

2. Rainfall

An average of 39mm of rain fell across the KSLES area in September, 69% of the LTA. Rainfall totals were generally higher in the east of the patch where catchments recorded normal rainfall totals for the time of year, whilst catchments in the west recorded below normal rainfall. The Thanet Chalk and Dover Chalk hydrological areas received the highest rainfall total in KSLES, 100% and 81% of the LTA, while the Lower Mole received the least rainfall with just 54% of the LTA.

September was a dry month, with an average of just seven wet days during the month. Rainfall was confined to a small number of events, accompanied by dry conditions between them. The highest daily rainfall total of 21.3mm was recorded at Hams Hill rain gauge in the Nort West Grain hydrological area in the second week of the month. Over the last 3 months, catchments in the west and central regions received exceptionally low rainfall, whilst the rest in the east saw notably low rainfall for the time of year, making this period the fourth driest three-month period since records began in 1871. Over the past 6 months, rainfall across the KSLES area was exceptionally low in all catchments, except Dover Chalk which saw notably low rainfall, making this period the second driest six-month period since records began in 1871. Over the past 12 months, rainfall received was normal in most southern catchments in KSL area, with catchments in the north receiving below normal rainfall.  

3. Soil moisture deficit and recharge

SMDs continued to rise across the KSLES area. Effective rainfall was 58% of the LTA in September, which, compounded with previous dry months, was insufficient to stabilise or reduce deficits. By month end, KSLES had a SMD of 197mm, increasing from 178mm in August. All hydrological areas recorded SMDs exceeding 160mm. In most areas, SMD was over 75mm higher than the LTA at the end of September.

4. River flows

Daily mean river flows generally increased throughout September. Flow monitoring sites in the KSLES area recorded mean flows ranging from notably low to normal. Flows at the Teise at Stonebridge and Dour at Crabble remained normal for the time of year. The Dour continued to benefit from groundwater contributions from the Dover Chalk aquifer. Flows in the Teise at Stonebridge are supported by releases from Bewl reservoir, which feeds into the Medway. Flows recorded in flashy rivers that are highly responsive to rainfall increased from exceptionally low to notably low. These are the Ravensbourne at Catford, Mole at Dorking, Eden at Vexour and Penshurst and Rother at Udiam. Flows at the Wandle at Connolly’s Mill and Stour at Horton rose from notably low to below normal, while the East Stour at South Willesborough remained notably low, and the Darent at Hawley remained below normal. However, flows at both sites did increase.

5. Groundwater levels   

Groundwater levels continued to decline seasonally across KSLES during September in response to the prolonged period of below normal rainfall. However, the rate of decline was generally less steep, and classifications remained largely the same as in August 2026. Sites monitoring groundwater in the Chalk aquifer recorded normal, below normal, and exceptionally low levels. The only sites recording levels below the normal range were Sweeps Land and Chipstead, both located in the western part of the KSLES area, with Chipstead experiencing a sharp decline from below normal to exceptionally low. Levels at Little Bucket, Riddles Lane, Fleete Reservoir, and Wolverton remained in the normal range. In the Lower Greensand aquifer, levels at Riverhead remained normal.

6. Reservoir stocks

Reservoir storage continued to decline throughout September, except for a marginal increase at Powdermill. By the end of the month, reservoirs in the KSLES area held the following live storage capacities and banding categories:

• Bewl – 49% below normal
• Bough Beech – 50% below normal
• Darwell – 34% notably low
• Powdermill – 32% notably low
• Weir Wood – 82% normal

Weir Wood reservoir remains offline.

7. Environmental impact 

Hands-off flow (HoF) restrictions continued to affect a number of catchments during September, although improving river flows at the start of the month allowed several restrictions in the Medway, North Kent, Stour and Rother catchments to be briefly lifted. Flow conditions subsequently deteriorated again later in the month, resulting in some restrictions being reintroduced during the final week of September. By month-end, widespread HoF restrictions remained in force across parts of the Medway, Stour, Rother, North Kent and Darent catchments.

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.