Research and analysis

Kent and South London water situation: May 2026 summary

Updated 11 June 2026

Applies to England

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

The Kent, South London and East Sussex (KSLES) area received 46% of the long term average (LTA) rainfall in May, with effective rainfall reaching just 10% of the LTA. Rainfall was predominantly below normal across the area, with notably low rainfall recorded in the west of the catchment. Soil moisture deficits (SMDs) increased to 99mm during May. Monthly mean river flows (MMFs) either decreased or stayed the same at key flow indicator sites in May. River flows varied across the area, ranging from exceptionally low to normal. Groundwater levels across KSLES continued to decline at all indicator sites. Reservoir storage levels also decreased during May, ranging from notably low to normal.

1. Rainfall

During May, the KSLES area received 46% of the LTA rainfall for the time of year, based on a whole-area average. Rainfall received in the KSLES area ranged from notably low in 4 out of 14 catchments in the west to below normal in the remaining 10 catchments in the east. The percentage of LTA rainfall received ranged from 37% in the South London catchment in the west of the patch, to 55% in the in the east. The highest daily rainfall total of 15.4mm was observed on day 18 of the month at Mayfield TBR in the Eastern Rother area. 

In May, the top 5 highest rainfall days were 18, 13, 2, 6, and 14 May. There were 8 dry days in May that recorded rainfall less than 0.2mm. The middle of the month saw scattered showers, while the beginning and end of the month were predominantly dry. A heatwave occurred late in the month, with temperatures reaching above 30°C. Overall, March, April, and May were the fourth driest 3-month period on record since records began in 1871.

2. Soil moisture deficit and recharge

SMDs across the KSLES area increased slightly during May, recording a deficit of 99mm, with the LTA being 64 millimetres. This reflects the exceptionally low rainfall experienced throughout the month. Effective rainfall recorded in May was 10% of the LTA.

Although SMDs increased during May, the rise was less pronounced than in April. The limited rainfall received during the month likely helped to slow the rate of soil drying very slightly, as reflected in the effective rainfall reaching 10% of the LTA, compared to negligible effective rainfall in April.

3. River flows

MMFs across the catchment are predominantly below normal to notably low, with several sites in the central and western areas, including the East Stour and South Willsborough, the Mole at Dorking and the Eden at Vexour/Penshurst, recording notably low flows. Exceptionally low flows are observed at the Ravensbourne at Catford. In parts of the north and east, sites such as the Darent at Hawley, Wandle at Connolly’s Mill and Dour at crabble Mill show normal flows. This pattern reflects both geology and recent dry conditions, with reduced flows seen not only in clay catchments but also extending into Greensand and some chalk-fed rivers following the recent lack of rainfall.

4. Groundwater levels   

Groundwater levels across the KSLES area have continued to fall steadily at all seven groundwater level sites. Levels across the catchment ranged from normal to above normal. Groundwater levels in the Chalk aquifer sites at Little Bucket remained above normal, while levels at Wolverton fell from above normal to the normal range this month. Chipstead, Sweeps Lane, Riddles Lane and Fleete Reservoir remained normal. In the Lower Greensand aquifer, levels at Riverhead remained in the normal range. The fall in groundwater levels is consistent with the lack of effective rainfall over the last 3-month period and the SMDs registered by the end of May.

5. Reservoir stocks

In the month of May, all 5 reservoirs saw a decrease in water levels. By the end of May, the reservoirs held the following live storage capacities and LTA class: 

• Bewl 91% – normal 

• Darwell 65% – notably low

• Bough Beech 89% – normal  

• Powdermill 71% – notably low  

• Weir Wood 98% – normal 

6. Environmental impact 

Hands‑off flow (HoF) restrictions were widespread across the Medway and Stour catchments, triggered in early and late April respectively, and persisted throughout May in line with flows. As flows declined further in late May, additional lower‑threshold restrictions were triggered in the Medway catchment and remained in place for the rest of the month. Warnings were also issued to abstractors in the Rother catchment during the last week of May, indicating a risk of restrictions in the coming weeks.

There were no fluvial or groundwater flooding alerts or warnings issued during May.

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.