Research and analysis

South-east England water situation report: July 2024 summary

Updated 14 August 2024

Applies to England

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

1. Summary

The south-east of England received 152% of the long term average (LTA) rainfall for July. The wettest days were 5 and 15 July, when the rainfall was widespread across the South east. It was the wettest July since 2012 for several areal rainfall units. After intense rainfall on 5 and 15 July, the soil moisture deficit (SMD) fluctuated but ended July close to the end of month LTA. The rivers had a largely a muted response to the heavy rainfall but remain in the above normal or higher categories as a legacy of the wet winter. There were 14 fluvial flood alerts and 2 fluvial warnings issued during the month. Groundwater levels have remained high across most sites, reflecting the cumulative effect of the significant rainfall in preceding months. Several sites recorded their highest or second highest groundwater levels on record.

2. Rainfall

The south-east of England received 152% of the LTA rainfall for July. The wettest days were 5 and 15 June, when the rainfall was widespread across the south-east. Together, the rainfall on these days accounted for an average of 42% of the monthly total. Both Hertfordshire and North London (HNL) and Thames (THM) recorded the wettest day on 5 July for the top 5 raingauge totals. To the south, the highest rainfall totals were recorded for both Kent and South London (KSL) and Solent and South Downs (SSD) on 15 July.

The highest daily rainfall totals were 46.9mm at Worsham (THM) and 46.2mm at Epping Forest (HNL) on 5 July, demonstrating how widespread the heavy rainfall was. There were on average, 16 ‘dry’ days when there was less than 0.2mm rainfall recorded.

The total rainfall for the period from April to July was the wettest since 2012 for several areal units, including:

• Chilterns East (HNL)
• Cotswolds West (THM)
• Thame (THM)
• Lower Lee (HNL)
• Lee Chalk (HNL)
• West Sussex Chalk (SSD)
• East Sussex Chalk (SSD)

3. Soil moisture deficit and recharge

The SMDs rose at the beginning of the month, fell after the rainfall on 5 July, then rose steadily again. On 15 July the deficits dropped again and eventually ended the month close to the LTA for July. As would be expected at this time of year, recharge was insignificant across the south-east of England.  

4. River flows

During July, the indicator flow sites continued to show the expected seasonal decline in flows. There was only a muted response to the heavy rainfall on both 5 and 15 July at most sites owing to the average soil moisture deficits. The 2 exceptions to this were the Ver at Colney Street and Mimram at Panshanger, both in HNL, which showed significant responses to the 2 rainfall events.

Despite the general seasonal decline in flows, of the 21 indicator sites, only 2 were in the normal category. These were the Coln at Bibury (THM) and the Rother at Udiam (KSL). Of the remaining 19 indicator sites, 7 were in the exceptionally high category. Six of these are chalk groundwater fed rivers and match the categories of the local groundwater sites. The Teise at Stonebridge (KSL) recorded exceptionally high flows owing to compensation flows.

Some notable observations for mostly groundwater fed rivers:

• Ver at Colney Street (HNL) recorded the highest July flow on record
• Coln at Bibury (THM) recorded its highest flows since 2014
• Thames at Farmoor (THM) recorded the fourth highest flow on record and the highest since 2012
• Kennet at Marlborough (THM) recorded its highest flows since 2012
• Mimram at Panshanger (HNL) recorded the second highest flow on record, the highest since 2001
• Lee at Feildes Weir (HNL) and Darent at Hawley (KSL) both had flows ranking as the third and fifth highest on record, the highest since 2012 and 2014, respectively

A total of 12 fluvial flood alerts and 2 fluvial flood warnings were issued during July.

5. Groundwater levels    

In July, groundwater levels showed seasonal declines and the influence of high rainfall in previous months. Despite the expected seasonal falls, many sites continued to maintain high groundwater levels.

Out of the 16 indicator sites, only 2 recorded levels in the normal category for July. These were Jackaments (THM) and Carisbrooke Castle (SSD). The remaining sites recorded levels above normal or higher. This reflects the cumulative effect of significant rainfall in preceding months.

The following sites recorded significant rankings:

• Wolverton (KSL, exceptionally high, highest on record)
• Stonor Estate (THM, exceptionally high, 2nd highest on record, highest since 2001)
• Lilley Bottom (HNL, exceptionally high, 3rd highest on record, highest since 2001)
• Ashley Green (HNL, notably high, 3rd highest on record, highest since 2001)
• West Meon (SSD, exceptionally high, 2nd highest on record, highest since 2001)
• Clanville Lodge (SSD, exceptionally high, 3rd highest on record, highest since 2001)

6. Reservoir stocks

The Lee reservoirs (HNL) recorded above the LTA storage for July. The reservoirs remain above average for July at all of the reservoirs across the south-east with just 2 exceptions. Both Arlington (SSD) and Powdermill (KSL) ended the month just below the monthly LTA. 

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.