Research and analysis

Water situation: August 2024 summary

Updated 11 September 2024

Applies to England

It has been a drier month across England with many catchments outside of the north-west receiving below average rainfall during August. England as a whole, received 65% of the 1961 to 1990 long term average (LTA) for August. Soil moisture deficits (SMD) have increased across most of England, with the exception of the north-west. Many catchments ended August with drier soils than at the start of the month. River flows decreased at the majority (90%) of indicator sites during August, however flows at four-fifths of sites continue to be classed as normal or higher for the time of year. Groundwater levels decreased at all but one reporting site, nevertheless levels across the country continue to be classed as normal or higher for the time of year. Reservoir storage decreased at 90% of the reservoirs we report on with most storage at most reservoirs classed as normal or higher. Reservoir stocks across England were 79% full at the end of August.

1. Rainfall

The rainfall total for England for August was 46.2mm which represents 65% of the 1961 to 1990 long term average for the month (67% of the 1991 to 2020 LTA), the majority (95%) of catchments received below average rainfall during August with central and east England reporting their driest August since 2003. The wettest hydrological areas relative to the LTA were the Esk (Cumbria) and Derwent in north-west England, which reported the wettest August since 1871 receiving 247% and 236% of LTA rainfall respectively. The driest hydrological area was the Ouse in south-east England which received only 24% of LTA rainfall in August. Three hydrological catchments in Yorkshire in the north-east were the driest since August 1995.

Rainfall totals during August varied across the country, with the majority (61%) of England’s areas classed as below normal or lower for the time of year. The greatest volume of rainfall was reported in the north-west of the country, where 4 catchments were classed as exceptionally high. Forty-three catchments (30%) were classed as normal for the time of year. Additionally, 45 catchments were classed as below normal with 41 classed as notably low for the time of year. Six catchments in the north-east and east England were classed as exceptionally low.

The 3-month cumulative totals were normal or lower across the majority of England with just over half of catchments in the north-east, east, and central parts of England classed as below normal. The 6-month cumulative totals across the majority of England were classed as either normal or above normal, reflecting the combination of above normal rainfall during the March to May period, and below normal between June to August. The 12-month cumulative totals were above normal or higher across England, with rainfall across the majority of catchments (90%) classed as exceptionally high; over a third of catchments reported either the wettest or second wettest September to August period since 1871.

2. Soil moisture deficit

With below average rainfall SMD increased across many parts of England, with only areas in the north-west reporting a decrease. SMD across England increased steadily throughout early and mid-August, before stabilising towards the end of the month as soils responded to the wetter conditions.

At a regional scale, soils across all areas of England with the exception of the north-west, remain drier than expected for the time of year, with SMD in north-west England around average for the time of year. Excluding the north-west, SMD across England increased and soils were drier at the end of August than they were at the end of July.

3. River flows

Monthly mean river flows decreased at most (89%) reporting sites during August, however the majority (84%) of sites continue to report monthly mean flows as normal or higher. Thirty-four sites (64%) were classed as normal for the time of year, 6 (11%) as above normal, with 3 (5%) sites each classed as notably high and exceptionally high. Flows at 9 sites (16%) were classed as below normal for the time of year.

Six regional index sites reported a decrease in monthly mean flows during August, only a single site, the River Lune in the north-west England recorded an increase in monthly mean flow. Flows at Orford on the Bedford Ouse were classed as above normal for the time of year. Naturalised flows at Kingston on the River Thames, the Great Stour in south-east England, the River Dove in central England, the south Tyne in the north-east, and the River Lune in the north-west all reported normal monthly mean flows. The River Exe in south-west England was the only index site where flows were classed as below normal or the time of year.

4. Groundwater levels   

At the end of August, groundwater level at almost all (96%) reporting sites recorded a decrease in levels, with only Crossley Hill in central England reporting an increase. However, levels at the majority of reporting sites (58%) are higher than expected for the time of year. Six sites (23%) were classed as exceptionally high, 9 sites (35%) as notably high, and 3 sites (12%) as above normal, with the remaining 8 sites (31%) classed as normal for the time of year. Four sites recorded their highest end of August level on record:

• Weir Farm (since 1983) in Bridgnorth Sandstone in central England

• Coxmoor (since 1990) in Idle Torne Sandstone in central England

• Priors Heyes (since 1972) in West Cheshire Sandstone in the north-west

• Skirwith (since 1978) in Carlisle Basin Sandstone in the north-west

Groundwater levels decreased at all aquifer index sites in August. Weir Farm (Bridgnorth Sandstone), Skirwith (Carlisle Basin Sandstone) and Stonor Park (South West Chilterns Chalk) were all classed as exceptionally high for the time of year. Levels at Little Bucket (East Kent Stour Chalk) and Redlands Hall (Cam and Ely Ouse Chalk) were notably high, with Dalton Estate (Hull and East Riding Chalk) classed as above normal. Levels at Chilgrove (Chichester Chalk) and Jackaments Bottom (Burford Jurassic Limestone) both in the south-east were classed as normal at the end of August.

5. Reservoir storage

Reservoir storage decreased during August at 90% of the reservoirs and reservoir groups we report on. The greatest stock decreases were at Ardingly and Bewl, both in south-east England which reduced by 17% and 18% full respectively. By the end of August, storage at almost all the reporting sites were classed as normal or higher for the time of year. The Dee system continues to be impacted by ongoing reservoir maintenance and was classed as below normal.

At a regional scale, reservoir storage decreased across England, with reductions of 10% or greater reported in south-east and south-west England. For England as whole, total storage decreased to 79% at the end of August.

6. Forward look

September is likely to experience warmer than average temperatures, and wetter than usual weather for the time of year. Unsettled, changeable conditions are forecast across the country through mid-September with an increased chance for longer spells of rain particularly across northern England. Any drier spells of weather are unlikely to be prolonged. Beyond mid-month there is a chance of a settled period of drier, warmer weather in the south and east however forecasts remain uncertain.

For the 3 month period between September and November, there is a higher than expected chance of warmer, wetter weather with an increased the likelihood of stormy conditions.

7. Projections for river flows at key sites

By the end of September 2024, river flows are projected to be normal or higher in east and south-east England, where many rivers are supported by groundwater discharge from porous aquifers. Across the rest of England, river flows are projected to be normal.

By the end of March 2025, flow at almost all the rivers across the country are projected to be normal or higher, with the greatest flows expected in the south-east, and east of England.

Author: National Water Resources Hydrology Team, nationalhydrology@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.