Research and analysis

South-east England water situation report: March 2026 summary

Updated 14 April 2026

Applies to England

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

1. Summary

It was a tale of two halves for March when only 59% of the monthly long term average (LTA) was recorded. This was the first month below average rainfall was recorded since November 2025. The first 15 days accounted for, on average, 81% of the total monthly rainfall. This drier month has reduced the total percentage of rainfall during the winter period (October to March) in all areas. For the South-east, there was 125% of the winter LTA. Soil moisture deficits (SMDs) stayed low and below average during the first half of the month, then rose steadily during the latter part of March. The month ended with above average SMDs for the South-east. The reduced rainfall in the second half of the month combined with the rising SMDs prevented much recharge occurring, with just over a third of the LTA being calculated for the South-east in March. River flows fell at most indicator sites across the South-east. Whilst these falling river flows reflected the below average rainfall in the second half of the month there were a number of responses in flows to the heavy rainfall in the middle of the month, particularly in SSD. Groundwater levels ranged from below normal at Jackaments (Thames, THM) to notably high in the Test and North Downs Chalk during the month. Levels peaked and then fell or continued to rise, albeit at a much slower rate during March.

2. Rainfall

It was a tale of two halves for March when only 59% of the monthly LTA was recorded. This was the first month below average rainfall was recorded since November 2025. The first 15 days accounted for, on average, 81% of the total monthly rainfall. Of this, most of the rainfall fell on the 6, 10 and 15 March. The total rainfall ranged from notably low in the far east of Kent to normal for much of the South-east. Hertfordshire and North London (HNL) was the wettest, where 70% of the LTA for March was recorded compared to just 51% of the LTA received in Kent and South London (KSL). The highest daily total was 18.3mm recorded at Kingsclere (THM) on the 12 March. The remaining top five highest daily totals were all recorded in Solent and South Downs (SSD), also on the 12 March and were all within 1mm of the highest total at Kingsclere. This drier month has reduced the total percentage of rainfall during the winter period (October to March) in all areas. For the South-east, there was 125% of the winter LTA. There was an east-west divide where THM and SSD both recorded 129% of the winter LTA and HNL and KSL recorded 118% and 115% LTA respectively.

3. Soil moisture deficit and recharge

The SMDs stayed low and below average during the first half of the month, then rose steadily during the latter part of March that reflected the two halves of the month in terms of rainfall. The month ended with above average SMDs for the South-east. The reduced rainfall in the second half of the month combined with the rising SMDs prevented much recharge occurring with just over a third of the LTA being calculated for the South-east in March. The total winter recharge (October to March) was around a third above average for the South-east as a whole, but ranged from just above average in HNL to almost one and a half times the LTA in SSD.

4. River flows

River flows fell at most indicator sites across the South-east. Whilst these falling river flows reflected the below average rainfall in the second half of the month, there were a number of responses in flows to the heavy rainfall in the middle of the month, particularly in SSD. Overall, flows ranged from below normal at Stonebridge (Teise, KSL) to notably high in the Test Chalk (SSD) and Marlborough (Kennet, THM) although just over half of the indicator sites were normal for March. Only 4 fluvial flood alerts were issued in March, but 14 groundwater flood alerts were still in force during the month. However, many of these were removed by the end of the month, leaving just five groundwater flood alerts still in force across the South-east by the end of March.

5. Groundwater levels  

Groundwater levels ranged from below normal at Jackaments (THM) to notably high in the Test and North Downs Chalk during the month. Rockley and Stonor (THM) were both above normal along with Little Bucket (KSL). Levels at Rockley peaked and fell during March while Stonor and Little Bucket continued to rise albeit at a much slower rate than previous months. Ashley Green and Lilley Bottom in the Chilterns and Upper Lee Chalk both continued to rise but remained at normal levels for March. The remaining sites across the North Downs Chalk, KSL, were all normal and generally continued to rise but at a much slower rate reflecting the lower rainfall, reduced recharge and rising SMDs.

6. Reservoir stocks

The reservoir storage during March was above average at most of the reservoirs in the South-east. Storage in Lower Thames (THM) and Darwell (KSL) was below average and Arlington (SSD) ended the month at the LTA for March.

Author: groundwaterhydrology@environment-agency.gov.uk 

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.