Research and analysis

Kent and South London water situation: March 2025 summary

Updated 14 April 2025

Applies to England

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

1. Summary

The whole of the Kent and South London (KSL) area received 12% of the long term average (LTA) rainfall during March. Rainfall received was exceptionally low across all catchments. The KSL area registered the driest March since 1990 and fifth driest March on record since records began in 1871. Soil moisture deficits (SMDs) increased in all catchments, ranging from 26mm to 50mm. Across the whole KSL area, on average, effective rainfall received this month was at 0% of the LTA. Monthly mean flows (MMFs) ranged from normal to exceptionally low in March in KSL. Six out of the 11 key flow sites saw below normal MMFs. Groundwater levels in the Chalk are predominantly normal for this time of year at the end of March. Groundwater levels at the Lower Greensand aquifer at Riverhead decreased and are now registering above normal levels. Levels at the end of the month at the 5 water company reservoirs in the area ranged from below normal to notably high.

2. Rainfall

The whole of the KSL area received 12% of the LTA rainfall during March. Rainfall received was exceptionally low across all catchments. The percentage of long-term average rainfall received ranged from 9% in the Darent rainfall area to 16% in the Eastern Rother rainfall area. The whole KSL area registered the driest March since 1990 and fifth driest March on record since records began in 1871. In the previous 3 months, spanning from January to March, normal rainfall was recorded across all catchments. In the previous 6 months, from September to March, rainfall was normal across most catchments. Only North West Grain and Sheppey rainfall areas in the north of the patch recorded below normal rainfall. In the last 12 months, rainfall ranged from above normal to below normal in KSL area. The highest daily rainfall total of 7mm for March was recorded at Pett STW TBR in the Eastern Rother catchment on 23 March. The next highest daily rainfall totals were on 12, 13, 29 and 21 March and ranged from 4mm to 3mm. One day with less than 0.2mm of rainfall was recorded this month.

3. Soil moisture deficit and recharge

At the end of March, SMDs increased in all catchments, ranging from 26 to 50mm. Thanet Chalk continued to be the only catchment registering higher SMDs when compared to other catchments of the patch. In March, all catchments registered slightly higher SMDs than long-term average. SMDs increased in all catchments due to the lack of effective rainfall in March. Across the whole area, on average, effective rainfall received this month was at 0% of the LTA. In March, the difference from LTA increased in all catchments.

4. River flows

MMFs ranged from normal to exceptionally low in March in KSL. River Wandle at Connolly’s Mill in the northwest, River Darent at Hawley and River Dour at Crabble Mill in the east saw normal flows. River Dour at Crabble Mill recorded the highest MMF percentage LTA of 115% for the month of March. Six out of the 11 key flow sites saw below normal MMFs. River Mole at Dorking and River Ravensbourne at Catford saw notably low and exceptionally low flows respectively. River Ravensbourne at Catford recorded the lowest percentage LTA of 40%.

5. Groundwater levels   

Groundwater levels in the Chalk are predominantly normal for this time of year at the end of March. Only groundwater levels at Riddles Lane and Wolverton are being registered as above normal. Groundwater levels at the Lower Greensand aquifer at Riverhead decreased and are now registering above normal levels. Groundwater levels in the Chalk are peaking or starting to decrease in most key monitoring points. The fall in groundwater levels is consistent with the effective rainfall of 0% of the LTA and the SMDs registered by the end of March.

6. Reservoir stocks

At the end of March, reservoir levels were:

• below normal at Darwell at 88%

• normal at Bewl at 90%  

• Weir Wood, Bough Beech and Powdermill reservoirs were full at the end of this month. Weir Wood reservoir remained offline during March

7. Environmental impact 

One fluvial flood alert was issued on 30 March.

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

Contact Details: 03708 506 507

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.