Research and analysis

Kent and South London water situation: August 2026 summary

Updated 14 September 2026

Applies to England

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

1. Summary

The dry weather was interrupted in August, with the Kent, South London and East Sussex (KSLES) area recording 60% of the long term average (LTA) rainfall for August. Soil moisture deficits (SMDs) remained largely the same as the end of July in response to limited effective rainfall levels, staying significantly higher than the LTA. River flows continued to fall throughout August but at a slower rate. Monthly mean flows ranged significantly across the area, with 2 sites recording normal flows and 4 sites recording exceptionally low flows. Groundwater level trends also remained similar to those at the end of July, with levels in the Chalk aquifer staying between normal and below normal and Lower Greensand aquifer levels remaining normal. Fleete Reservoir was the only site to change banding, moving from below normal to normal. Reservoir storage levels continued to decrease throughout August, ranging from exceptionally low to above normal. However, they are tracking slightly steeper than normal drawdown rates. 

2. Rainfall

An average of 35mm of rain fell across the KSLES area in August, 60% 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 to exceptionally low rainfall. The Dover Chalk hydrological area received the most rain in KSLES 79% of the LTA, while the Lower Mole received the least rain with just 28% of the LTA. 

The first 2 weeks of August were very dry, with only small, scattered showers, whilst the second 2 weeks were much wetter, with the highest daily rainfall total of 23.8mm being recorded at Throwley Rain Gauge in the North Kent hydrological area. Over the last 3 months, rainfall was notably low across western catchments, while eastern catchments recorded below normal rainfall. Over the past 6 months, all catchments recorded exceptionally low rainfall, making this period the fourth driest since records began in 1871. Over the past 12 months, most catchments recorded normal rainfall, except for 4 catchments in the north of the patch which recorded below normal rainfall.

3. Soil moisture deficit and recharge

Despite the rainfall received during August, SMDs continued to rise across the KSLES area. Effective rainfall was 45% of the LTA in August, which, compounded with previous dry months, was insufficient to stabilise or reduce deficits. By month end, KSLES had a SMD of 178mm, increasing from 155mm in July. Most hydrological areas recorded deficits over 160mm, except for 2 areas that recorded levels between 131mm and 160mm. In most areas, SMD was 51mm to 75mm higher than the LTA at the end of August. 

4. River flows

Daily mean river flows generally continued to fall throughout August in response to the below average rainfall; however, for some sites the decline in flows was relatively small. Flow monitoring sites in the KSLES area recorded mean flows between normal and exceptionally low. Normal flows were seen at the Teise at Stonebridge and Dour at Crabble. The Dour continued to benefit from typical 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. Exceptionally low flows have been recorded in flashy rivers that are highly responsive to rainfall. These are the Ravensbourne at Catford, Mole at Dorking, Eden at Vexour/Penshurst and Rother at Udiam. However, flows have increased or stayed the same at all sites that recorded exceptionally low flows.

5. Groundwater levels   

Groundwater levels continued to decline seasonally across KSLES 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 July 2026, except for Fleete Reservoir which has risen from below normal to normal levels. Sites monitoring groundwater in the Chalk aquifer recorded normal and below normal levels. The only sites that are recording levels in the below normal class, namely Chipstead and Sweeps Lane, are situated in the western part of the KSLES area. In the Lower Greensand aquifer, levels remained in the normal range.

6. Reservoir stocks

Reservoir storage continued to fall throughout August. By the end of the month, reservoirs in the KSLES area held the following live storage capacities and banding categories:

• Bewl – 58% normal
• Bough Beech – 58% normal
• Darwell – 48% below normal
• Powdermill – 31% exceptionally low
• Weir Wood – 85% above normal

Weir Wood reservoir remains offline.

7. Environmental impact 

Hands-off flow (HoF) restrictions remained widespread throughout August across the Medway, Stour, and Rother catchments. Restrictions introduced in the Medway and Stour catchments during March and April, and in the Rother catchment during mid-June, persisted throughout the month. Additional HoF restrictions were triggered during the first week of August across the Medway, Rother, North Kent, and Darent catchments. Following these early August triggers, no further HoF restrictions were implemented during the remainder of the month.

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 herein.