Research and analysis

South-east England water situation report: April 2026 summary

Updated 13 May 2026

Applies to England

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

1. Summary

April weather was dominated by a static anticyclone which blocked North Atlantic low pressure systems. As a result, April was a dry month with only 15% of the long term average (LTA) rainfall recorded across the south-east of England. The distribution of rainfall was roughly east-west. Most of Thames (THM) and Solent and South Downs (SSD) had rainfall in the notably low category with Hertfordshire and North London (HNL) and Kent and South London (KSL) in the exceptionally low category. The higher than average soil moisture deficit (SMD) across the south-east from the end of March continued throughout April, and rose steadily to end the month at around twice the LTA for April.

River flows declined during April, continuing the seasonal trend which many of the indicator sites started in late February. Around half of the indicator sites were normal for April. The expected steady decline of groundwater levels for this time of year continued during the month for most of the indicator sites. Levels ranged from notably low (Jackaments, THM) to notably high (West Meon, SSD). Most of the groundwater flood alerts were removed during April, leaving one in THM. No fluvial flood alerts were issued during the month.

2. Rainfall

April weather was dominated by a static anticyclone which blocked North Atlantic low pressure systems. As a result, April was a dry month with only 15% of the LTA rainfall recorded across the south-east of England. This was the second consecutive month of below average rainfall across all 4 areas. The distribution of rainfall was roughly east-west. Most of THM and SSD had rainfall in the notably low category but HNL and KSL, both with 10% of the LTA monthly rainfall, were exceptionally low THM was marginally the wettest area with 20% of the LTA rainfall. Lee Chalk (HNL) had the fourth driest April on record, with April 2021 drier. For the 2 months ending April, Romney Marsh, Dover Chalk and Thanet Chalk (all KSL) were the driest since 1997, ranking third driest on record.

The highest daily rainfall total was 12.5mm, recorded at Northfleet, KSL on 13 April. Rainfall on 11, 12 and 13 April accounted for the top 5 rainfall totals for all 4 areas of the south-east of England. The rainfall from 12 to 15 of the month accounted for around 50% of the month’s total rainfall. On average there were 24 ‘dry’ days (less than 0.2mm rainfall in a day). These were distributed either side of the wetter few days mid-month.

3. Soil moisture deficit and recharge

The higher than average SMD across the south-east from the end of March continued throughout April, and rose steadily to end around twice the LTA for April. The SMDs for SSD were close to 3 times the LTA for April. Unsurprisingly, the recharge across the south-east during April was negligible as a result of the low rainfall combined with the high SMDs.

4. River flows

River flows declined during April, continuing the seasonal trend which many of the indicator sites started in late February. Around half of the indicator sites were normal for April, mainly supported by groundwater. Four sites supported by relatively high groundwater levels were in the above normal band. These included the Test at Allbrook and Highbridge (SSD) and the Mimram at Panshanger (HNL). Rivers draining impermeable catchments recorded flows in either the below normal or notably low bands. These included the Loddon at Sheepbridge (THM) and the Medway at Teston and East Farleigh (KSL) which were both below normal and the Lymington River at Brockenhurst (SSD) that was notably low. The Arun at Alfoldean, also in the notably low category, recorded the fourth lowest April flow on record, after 2011. There were no fluvial flood alerts during the month.

5. Groundwater levels   

The expected steady decline of groundwater levels for this time of year continued during the month for most of the indicator sites. Lilley Bottom (HNL) levels peaked during April. Levels ranged from notably low (Jackaments, THM) to notably high (West Meon, SSD) Ten of the 16 indicator sites were in the normal band. Generally, the sites in the higher categories were in the Test Chalk or the South Downs, which demonstrated a residual response to the heavy rainfall and recharge during the winter which impacted the south coast. The exception to this was Little Bucket (KSL), North Downs, that had levels in the above normal category .The groundwater flood alerts issued in KSL and SSD were removed during April, leaving one in THM.

6. Reservoir stocks

The reservoir storage during April was above average at half of the reported reservoirs in the south-east, although levels have dropped slightly. Storage in Lower Thames (THM), Darwell and Powdermill (both KSL) and Arlington (SSD) ended the month below the LTA for April.

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.