Kent and South London water situation: May 2025 summary
Updated 12 June 2025
Applies to England
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1. Summary
The Kent and South London (KSL) area as a whole received 35% of its long term Average (LTA) rainfall in May. Soil moisture deficits (SMD) continued to increase and ended the month above the LTA. Monthly mean river flows (MMFs) varied between exceptionally low and normal, with most in the normal range. Groundwater levels continued to decline at all our key indicator sites throughout May and ended the month in the normal category. Reservoir levels also continued to decline and varied between normal and exceptionally low.
2. Rainfall
The whole KSL area received 35% of the LTA rainfall during May. Rainfall received was notably low across most catchments. Three catchments received below normal rainfall. The percentage of LTA rainfall received ranged from 22% in the Thanet Chalk in the East to 70% in the Lower Mole area in the West. In the previous 3 months, spanning from March to May, exceptionally low rainfall was recorded in most catchments in line with the low rainfall received. The KSL area registered the fourth driest 3 months spanning March to May on record since records began in 1871. In the previous 6 months, from December to May, rainfall was notably low in the north of the catchment, below normal in the south. In the last 12 months, rainfall ranged from normal to exceptionally low in KSL area. The highest daily rainfall total of 19.5mm for May was recorded at Leatherhead rain gauge in the North downs – South London catchment on 2 May. The next highest daily rainfall totals were on 11, 21, 27 and 23 May and ranged from 13.9mm to 8.2mm. Ten days with less than 0.3mm of rainfall were recorded this month.
3. Soil moisture deficit and recharge
At the end of April SMDs ranged from 41mm to 130mm. At the end of May, SMD had increased further, now ranging from 71mm to 160mm. In May, all catchments registered higher SMDs than the LTA. SMDs increased in all catchments due to the lack of effective rainfall in May. Across the whole area, on average, effective rainfall received this month was 9% of the LTA.
4. River flows
MMFs ranged from normal to exceptionally low in May in KSL. Notably low flows were recorded in 3 of the 11 sites, these were the:
- River Mole at Dorking
- River Eden at Vexour and Penshurst
- East Stour at South Willesborough
One Exceptionally low flow was recorded at River Ravensbourne at Catford. River Dour at Crabble Mill recorded the highest MMF percentage LTA of 99% for the month of May. River Ravensbourne at Catford recorded the lowest percentage LTA of 36%. The fall in MMFs is consistent with the effective rainfall of 9% of the LTA and the SMDs registered by the end of May.
5. Groundwater levels
At the end of May, groundwater levels in the Chalk were declining at normal levels for this time of year. Groundwater levels at the Lower Greensand aquifer at Riverhead have also continued to decrease, and they are now within the normal range. Levels in all monitoring points have continued to fall since the end of April. The fall in groundwater levels is consistent with the effective rainfall of 9% of the LTA and the SMDs registered by the end of May.
6. Reservoir stocks
Throughout May, water levels in all the water company reservoirs declined.
At the end of May, reservoir levels were:
- exceptionally low at Darwell – 68% full
- below normal at Bough Beech – 84% full
- normal at Weir Wood – 96% full, Powdermill – 89% full and Bewl – 82% full
7. Environmental impact
On 1 May, a small number of constraints were applied to abstractors in the Medway and Stour catchment, for licences linked to Stilebridge and Littlebourne gauging station.
Similarly, on 12 May, constraints were imposed on abstractors in the Stour catchment, with licences linked to Poulton Farm gauging station.
Finally, on 16 May, a single constraint was imposed on abstractors in the Medway catchment, with licences linked to Teston gauging station. The bulk of Teston constraints were applied on 3 April and have persisted throughout the months of April and May.
Constraints were applied to abstractors in the Stour catchment linked to the Wye gauging station on 23 April, and have continued throughout the month of May due to the hydrological conditions.
Despite below LTA rainfall for the last 3 consecutive months, due to groundwater influences within catchments the Areas water resources status remains normal.
Author: Groundwater and Hydrology Team, ksl.gwh@environment-agency.gov.uk
Contact Details: 03708506506
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.