Research and analysis

Water situation: August 2023 summary

Updated 11 January 2024

Applies to England

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

August rainfall totals were in the normal range across most of England, with almost two-thirds of catchments receiving above average rainfall, and the remaining catchments recording below average rainfall. This mixed picture was reflected in soil moisture deficits (SMD) with wetter than excepted soils in the south-west and northern England, and drier than expected soils in the east and south-east. River flows reduced at many sites as rivers recovered from very wet conditions in July, although the majority of sites recorded above normal or higher monthly mean flows. Groundwater levels decreased at almost all sites, as is expected in the late summer, and two-thirds were classed as normal for the time of year. Reservoir stocks declined at two-thirds of the reservoirs or reservoir groups we report on, with almost half of reservoirs classed as normal for the time of year.

1. Rainfall

The August rainfall total for England was 72mm which represents 102% of the 1961 to 1990 long term average (LTA) for the time of year (96% of the 1991 to 2020 LTA). Two-thirds of catchments received average or above average rainfall during August, while the remaining third received below average rainfall. The wettest hydrological area relative to the LTA was the Isle of Wight on the south coast which received 167% of LTA rainfall. The driest hydrological area was the Soar catchment in central England which received 64% of LTA rainfall in August.

August rainfall totals were classed as normal for the time of year in almost all catchments across England. Eleven hydrological areas in north-east, east and south-east England were classed as above normal for the time of year. In central England and the far north of England 5 hydrological areas received below normal rainfall during August. All regions received normal rainfall in August, as did England as whole.

The 3 month cumulative rainfall totals were normal for most of central, east and south-east England. In south-west, north-west and north-east England cumulative rainfall totals for June to August were above normal or higher, with exceptionally high totals in parts of the north-west. The 6 month cumulative rainfall totals were above normal or higher across almost all of England, with a handful of hydrological areas recording normal cumulative rainfall totals for the period. The south-west and north-west were particularly wet over the March to August period, with exceptionally high cumulative rainfall totals in many catchments. The twelve month cumulative rainfall totals tell a similar story, with above normal or higher totals in the majority of catchments. Much of the south coast and parts of the north-west recorded exceptionally high rainfall totals over the past twelve months, with England as a whole recording notably high cumulative rainfall.

2. Soil moisture deficit

SMDs were similar at the end of August to where they had been at the end of July. Parts of south-east and east England saw a slight increase in SMD by the end of August, while parts of the north-east saw SMDs decrease. This strengthened the north-west to south-east divide, with drier soils in the south-east and wetter ones in the north-west.

SMDs in the south-east and east were above the LTA in many places, meaning soils were drier than would be expected for the time of year. In comparison in the south-west, central, north-west and north-east of England SMDs were below the LTA, leaving soils wetter than expected at the end of August.

3. River flows

August monthly mean river flows decreased at more than half of all indicator sites we report on, while the remaining sites recorded increases in monthly mean river flows. The majority of sites were above normal or higher for the time of year, with the remainder being normal or below normal. All 3 below normal sites were in south-east and east England. The River Derwent and River Wear in the north-east, the River Weaver in the north-west and the River Brue in south-west England all had monthly mean river flows classed as notably high for the time of year.

Monthly mean river flows decreased at all except one of the regional index sites in August, with Thornton on the River Exe in south-west England seeing an increase in flows which meant it was classed as above normal for the time of year. Naturalised flows on the River Thames in the south-east and South Tyne in the north-east were also above normal for the time of year. The Great Stour in south-east England, the River Lune in north-west England, the River Dove in central England and the Bedford Ouse in east England all recorded normal monthly mean river flows for the time of year.

4. Groundwater levels

By the end of August groundwater levels had decreased at almost all of the indicator sites we report on. At 3 sites groundwater levels remained the same between the end of July and the end of August. Almost two-thirds of groundwater sites were classed as normal for the time of year at the end of August. The remaining sites were all above normal or higher. Clanville Lodge Gate in the Test Chalk in south-east England was notably high while Washpit Farm in the North West Norfolk Chalk in east England was below normal for the time of year. Groundwater levels in the West Cheshire Sandstone at Priors Heyes in north-west England continue to recover from the effects of historic abstraction and remain in the exceptionally high classification.

The major aquifer index sites reflected this largely normal picture, with just 2 sites above normal for the time of year, Skirwith in the Carlisle Basin and Eden Valley Sandstone and Little Bucket in the East Kent Stour Chalk. Chilgrove in the Chichester Chalk returned to normal levels for the first time since it saw rapid increases in groundwater levels in the spring. The remaining major aquifer index sites were all normal for the time of year.

5. Reservoir storage

Reservoir storage during August declined at more than two-thirds of the reservoirs or reservoir groups we report on, although most reservoirs saw storage changes of less than 5%. Three reservoirs or reservoir groups recorded unseasonal increases of storage greater than 10%, Teesdale group in north-east England, Haweswater and Thirlmere in north-west England and Vyrnwy in north Wales which part supplies north-west England. At the end of August these changes meant that almost half of the reservoirs and reservoir groups we report on were classed as normal for the time of year. Four sites were below normal or lower, with Colliford and Roadford in south-west England below normal for the time of year, while Kielder in the north-east was also below normal and the Dee System in Wales was notably low as a result on ongoing engineering works. In contrast, more than a third of reservoirs were above normal or higher for the time of year, including 7 reservoirs classed as above normal, and 5 classed as notably high or higher at the end of August.

At a regional scale, total reservoir storage decreased in east, north-east, south-east and south-west England. In central and north-west England total reservoir storage increased slightly at the end of August. For England as a whole total reservoir storage has remained the same between July and August at 82%.

6. Forward look

Although average rainfall and temperature is forecast, the early and mid-September period is likely to experience unsettled conditions, varying from scattered showers to warm sunny spells across the country. Northern England is expected to experience greater rainfall and more frequent changes in weather than the south. Conditions are likely to remain changeable throughout September, with a higher likelihood of unseasonably warm dry spells towards the end of the month.

For the UK for the 3 month period from September to November there is a higher than usual chance of warmer weather, although near average temperatures are most likely. The likelihood of either a wet or dry period are similar to expected for the time of year.

7. Projections for river flows at key sites

By the end of September 2023, the majority of rivers throughout England have a greater likelihood of experiencing either above normal or normal flows, Stiffkey in east England, is the only river where projections show a high likelihood of below normal flows. September projections show a split with a greater chance of lower flows throughout east England and higher flows in the west. A similar trend can be observed in the projections through to March 2024; where the majority of rivers across England are likely to experience normal flows or greater, while rivers in the east and south-east have an increased chance of experiencing below normal flows compared to the rest of the country.

8. Projections for groundwater levels in key aquifers

By the end of September 2023, groundwater levels are most likely to be in their expected range across the majority of England. Groundwater levels in south-east, south-west and north-east of England have a greater likelihood of experiencing above normal or higher levels.

By the end of March 2024, groundwater levels throughout England are expected to be normal. With sites located along the eastern coast and south-east more likely to experience below normal levels. However, sites supported by the Chalk aquifer in the south-east of England are likely to experience above normal or greater levels. Skirwith in the north-west is the only location with a high likelihood of notably high groundwater levels.

Author: National Water Resources Hydrology Team, [email protected] 03708 506 506

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.