Research and analysis

South-east England water situation report: August 2026 summary

Updated 14 September 2026

Applies to England

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

1. Summary

August was another dry month with only 55% of the long term average (LTA) rainfall recorded. The month started dry and hot with a static anticyclone over England continuing the trend from July. The month was mostly dry until thunderstorms and widespread heavy showers fell from 26 August, providing around 80% of the monthly total. The soil moisture deficits (SMDs) rose steadily during the month, with some hydrological areas having their highest August SMDs on record. There was no significant recharge during the month.

The seasonal flow recession continued for the 21 flow indicator sites across the south-east. There was little or no response to the rainfall at the end of the month at the indicator sites, reflecting the high SMDs prevalent in the catchments, however, 11 fluvial flood alerts were issued during the month. Groundwater levels continued to decline during August. Most of the water companies that operate across the south-east now have issued temporary use bans (TUBs) as a result of the ongoing hot, dry conditions of the last couple of months. The West Berkshire Groundwater Scheme (Thames, THM) has been switched on during the month in order to supplement the flows in the River Thames and to bolster the water available for abstraction in the Lower Thames.

2. Rainfall

August was another dry month with only 55% of the LTA rainfall recorded. The month started dry and hot with a static anticyclone over England continuing the trend from July. There was a heat alert issued on 10 August for 4 days, the fifth of the summer. On 19 August a narrow band of heavy rainfall cut across the south coast, resulting in the highest daily rainfall total for the month, 45.7mm, being recorded at Pevensey, Solent and South Downs (SSD). The month was mostly dry until thunderstorms and widespread heavy showers fell from 26 August, providing around 80% of the monthly total. The remaining monthly rainfall fell in the last 6 days, the highest totals recorded on 26 and 30 August. The top 5 daily rainfall totals for the south-east were all recorded in SSD.

Although the south-east received only 55% of the LTA rainfall during August, when taking July into consideration, there were some record breaking statistics. It was the driest two-month period ending in August on record for the south-east, Hertfordshire and North London (HNL), and for 12 of the 46 hydrological areas across the south east.

3. Soil moisture deficit and recharge

The SMDs rose steadily during the month. There were slight reductions in the SMDs in hydrological areas in southern SSD after the rainfall on 19 August and further small reductions across the south-east after the rainfall in the last 6 days of the month. However, SMDs remained above the LTA for August, and in some cases almost double the LTA. For example, estimates of the SMDs for the end of August for:

• Chilterns West (Thames, THM), Chilterns East (HNL) and Test Chalk (SSD) were the highest on record (from 1962)
• Berkshire Downs and Wey Greensand (both THM) were the second highest on record, after 1976

After the relatively dry month and continuing high SMDs, there was no significant recharge during August.

4. River flows

The seasonal flow recession continued for the 21 flow indicator sites across the south-east. The ranking of the flows largely matched the permeable or impermeable nature of the catchments. There were five sites in the exceptionally low category, including the River Thames at Kingston (THM), the River Lymington at Brockenhurst (SSD) and the River Rother at Udium (Kent, South London and East Sussex,KSLES). Eight of the indicator sites were in the normal range for August, mainly draining groundwater-fed catchments. These included the River Ver at Panshanger (HNL), the River Itchen at Allbrook and Highbridge (SSD) and the River Dour at Crabble Mill (KSLES).

The River Coln at Bibury and the River Thames at Farmoor (both THM) recorded their third lowest August flow on record, the lowest since 2022. A number of other indicator sites also recorded their lowest flows since 2022, including the River Thames at Kingston (THM), the River Mimram at Panshanger (HNL) and the River Darent at Hawley (KSLES). There was little or no response to the rainfall at the end of the month at the indicator sites, reflecting the high SMDs prevalent in the catchments. However, locally there were 11 fluvial flood alerts all issued on the 26 August.

5. Groundwater levels   

The expected steady decline of groundwater levels for this time of year continued during the month. Nine of the 16 indicator sites remained in the normal range for August, reflecting the legacy of the recent winter recharge. The remaining seven indicator sites were in the below normal or lower range for the month. Levels in the more responsive chalk sites, for example Chilgrove (South Downs, SSD), Rockley (Berkshire Downs, THM) and Chipstead (North Downs, KSLES) have fallen to the notably low (Chilgrove) and below normal range. The Oolites of the Cotswolds responded very quickly to the dry conditions during the summer and levels at Jackaments (THM) continued to be exceptionally low at the end of August.

6. Reservoir stocks

The high temperatures and lack of rainfall has resulted in some significant declines in reservoir storage. All of the reservoirs recorded below LTA storage for August with one exception being Weir Wood (KSLES) which ended the month above the LTA.

Most of the water companies that operate across the south-east have now issued temporary use bans (TUBs) as a result of the ongoing hot, dry conditions of the last couple of months.

The West Berkshire Groundwater Scheme (THM) has been switched on during the month in order to supplement the flows in the River Thames and to bolster the water available for abstraction in the Lower Thames.

Author: HNL Groundwater and Hydrology, 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.