South-east England water situation report: April 2025 summary
Updated 15 May 2025
Applies to England
漏 Crown copyright 2025
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1. Summary
April was the second consecutive month with below average rainfall, with only 48% of the average long term average (LTA) rainfall. The anticyclonic conditions which built over the country during March continued for most of April. The month鈥檚 rainfall fell on 6 days between 14 and 22 April during a brief unsettled period. The soil moisture deficits (SMD) rose steadily to end more than 3 times the LTA for April, with no significant recharge. The expected seasonal decline in the river flow hydrographs continued during April. The rainfall showed very little impact on the flows. Similarly, the steady decline of groundwater levels continued during the month. Three residual flood alerts remained during the month, 2 groundwater and one fluvial.聽 聽
2. Rainfall
April was the second consecutive month with below average rainfall, with only 48% of the average LTA rainfall. On average there were 24 鈥榙ry鈥� days where the daily rainfall total was less than 0.2mm. The anticyclonic conditions which built over the country during March continued for most of April. The month鈥檚 rainfall fell on 6 days between 14 and 22 April during a brief unsettled period. The highest daily totals were recorded on April 22 for all 4 areas in the south-east. The highest daily total was 24mm, recorded at Chenies, Hertfordshire and North London (HNL). Kent and South London (KSL) also recorded significant rainfall totals on 14 April, with Lenham, Stour, recording 18.3mm on that date. On average, the rainfall totals for 22 and 14 April accounted for 77% of the monthly total across the south-east of England.
March and April total rainfall was the lowest since 2011 for the south-east, Thames (THM), Solent and South Downs (SSD) and was the fourth driest 2 month period ending in April for a number of areal units, including:
- Cotswolds West (THM)
- Berkshire Downs (THM)
- Upper Thames (THM)
- Ock (THM)
- Test Chalk (SSD)
3. Soil moisture deficit and recharge
The SMDs rose steadily to end more than 3 times the LTA for April. There were slight falls in the SMD after the rainfall on 14 and 22 April, but the general trend after the rainfall was a steady climb during the month. As there were significant SMDs, there was limited recharge during the rainfall events.
4. River flows
The expected seasonal decline in the river flow hydrographs continued during April. The rainfall showed very little impact on the flows for rivers draining both impermeable and permeable catchments. This is largely due to the high SMDs. More than half the key indicator flow sites were in either the normal or below normal category. The normal sites were largely draining permeable catchments and the below normal sites were in impermeable catchments. The legacy of exceptionally high rainfall remains evident in the chalk of northern HNL, with both the Mimram and Ver recording exceptionally high flows for April. One fluvial flood alert remains in force for the Mimram in HNL.
5. Groundwater levels听听听听聽聽聽
The expected steady decline of groundwater levels for this time of year continued during the month for all the indicator sites in the south-east of England. Jackaments (THM) recorded levels in the exceptionally low category and demonstrates the rapid decline of groundwater in oolitic limestone to periods of dry weather. By contrast, Stonor (THM) recorded the fifth highest and Lilley Bottom (HNL) the fourth highest April levels on record, falling in the exceptionally high and notably high categories respectively. Ten of the 16 key groundwater sites recorded levels in the normal category for April. Two groundwater flood alerts remain in force in HNL and THM.
6. Reservoir stocks
The dry and warmer weather has resulted in slight declines in some of the reservoir stocks across the south-east of England. Ardingly and Arlington (both SSD) and Darwell (KSL) ended the month below the LTA for April. Lower Thames, Farmoor (both THM), and Bewl (KSL) remain close to the LTA storage. Lower Lee (HNL), Bough Beech, Powdermill and Weir Wood (all KSL) have above the LTA storage.
Author: [email protected] 听听听听
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.