Research and analysis

Kent and South London water situation: March 2024 summary

Updated 15 April 2024

Applies to England

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

1. Summary

The whole of the Kent and South London area received 140% of the long-term average rainfall during March. Rainfall received across catchments in the area ranged from above normal to notably high for this time of the year. At the end of March, Kent and South London area saw the third wettest winter (October to March) on record. Soil moisture deficits throughout all 13 of the rainfall areas were less than or equal to 10mm. Monthly mean river flows for March ranged from exceptionally high to notably high in the Kent and South London area. Groundwater levels ranged from above normal to exceptionally high in the Chalk aquifers and were exceptionally high in the Lower Greensand aquifers at Riverhead. Levels at the 5 water company reservoirs ranged from exceptionally high to notably high in the Kent and South London area.

2. Rainfall

The whole of the Kent and South London (KSL) area received 140% of the long-term average (LTA) rainfall during March. Rainfall received across catchments in the area ranged from above normal to notably high. Most catchments in the north and east of KSL received rainfall above normal, while catchments in the west received notably high amounts of rain for this time of year. The highest daily rainfall total of 20.4mm for March occurred on the tenth day of the month and was recorded at Trosley PS rain gauge in the North Kent Chalk catchment. Days 26, 12, 5 and 27 had the next highest daily rainfall totals that ranged from 15.4mm to 19.2mm. During the previous 3 months, which spanned from January to March, rainfall was exceptionally high in catchments in the south and notably high in catchments in the north. In the previous 6 months, spanning October to March, rainfall across the Kent and South London area was exceptionally high in all catchments except for Sheppey in the north. KSL area saw the third wettest winter since records began in 1872. The last 12 months saw rainfall that was exceptionally high in catchments in the south and notably high and above normal in catchments in the north.

3. Soil moisture deficit and recharge

At the end of March soil moisture deficits (SMDs) throughout all 13 of the rainfall areas in Kent and South London were less than or equal to 10mm. SMDs were, on average, considerably wetter than the long-term average for the last day of March. SMDs had a minimal increase compared to February. This is consistent with the amount of effective rainfall KSL received this month which was 176% of the LTA across the whole area, drier than February. Aquifers continue to remain highly responsive, and depending on their intensity, rainfall events are resulting in groundwater levels rising after relatively short time periods.

4. River flows

Monthly mean river flows (MMFs) for March ranged from notably high to exceptionally high. The latter category was seen the most during March at key flow sites, whereas only 3 flow sites saw notably high MMFs. These sites are in the North-West and central South of the patch. The key flow site with the highest MMF banding was the Eden at Vexour/Penshurst, which saw 261% of the LTA for the month of March. The lowest percentage of LTA monthly mean river flow was observed at the Wandle at Connollys Mill, which recorded 145% of the LTA.

5. Groundwater levels   

Groundwater levels in March 2024 were exceptionally high in the Chalk across KSL area, except for Riddles Lane and Fleete Reservoir in the northeast where levels were notably high and Sweeps Lane in the northwest, where levels were above normal for this time of the year. Groundwater levels in the Greensand at Riverhead were exceptionally high. Due to the continued above average effective rainfall and low SMDs across the KSL area, groundwater levels in the Chalk and Lower Greensand aquifers continued to rise in March. Aquifers continue to be highly responsive, and spells of heavy, intensive rainfall would have the potential for groundwater to rise more rapidly, within relatively short time periods. 

Due to the rise in groundwater levels in East Surrey and South London that occurred since February, a flood alert for groundwater flooding was issued on the 6 March, and it is still in effect for South East London area. The flood alert for the area of East Kent issued in December 2023 is still in effect. However, during the next months, we expect periods of weather with sunnier and warmer conditions. As a result of these conditions, effective rainfall/aquifer recharge will diminish, which in turn will lead to a fall of groundwater levels until the onset of the next recharge season.

6. Reservoir stocks

At the end of March, reservoir levels were normal at Darwell at 96.5%, notably high at Bough Beech at 100% and above normal for this time of year at Weir Wood and Powdermill both at 100% and Bewl with a level of 99.6%. Weir Wood, Powdermill, Bough Beech were considered full at the end of the month. The levels at Bewl reservoir have recovered from the planned operational works that previously drew them down and are now above normal for this time of year. Most of the levels in the reservoirs remained unchanged throughout the month of March, however water levels in Darwell reservoir have minimally decreased. 

7. Environmental impact 

Forty-six flood alerts were issued on 1, 2, 11, 12 and 28 March. A new groundwater flooding alert was issued for South London East in March 2024 and the groundwater flooding alert for East Kent has remained in force.

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

Contact details: 0370 850 6506

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.