Research and analysis

Water situation: September 2023 summary

Updated 11 January 2024

Applies to England

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

September rainfall totals were in the normal range across most of England, with almost all catchments receiving average or above average rainfall. Soil moisture deficits (SMD) reduced across England during September as soils became wetter in many areas. River flows reduced at most of sites we report on but the majority of sites recorded normal or higher monthly mean flows. Groundwater levels decreased at almost all sites, but remain classed at normal at more than two–thirds of sites for the time of year. Reservoir stocks declined at three-quarters of the reservoirs or reservoir groups we report on, with almost two-thirds of reservoirs classed as normal for the time of year.

1. Rainfall

The September rainfall total for England was 81.7mm which represents 116% of the 1961 to 1990 long term average (LTA) for the time of year (119% of the 1991 to 2020 LTA). Nearly all catchments received average or above average rainfall during September, while only 6 catchments received below average rainfall. The wettest hydrological area relative to the LTA was the Lower Welland and Nene catchment in east England which received 178% of LTA rainfall. The driest hydrological area was the Thanet Chalk in south-east England which received only 37% of LTA rainfall in September.

September rainfall totals were classed as normal for the time of year in most catchments across England. Nearly a third of catchments were classed as above normal and 7 catchments, predominately in the north-west were classed as notably high for the time of year. Across south-east and east England, 6 hydrological areas received below normal rainfall during September. All regions, with the exception of north-west England, where rainfall was above normal, received normal rainfall in September, as did England as whole.

The 3 month cumulative rainfall totals were above normal or higher at nearly three-quarters of catchments across England. Nine catchments mainly in the north-west have rainfall totals classed as exceptionally high for July to September. The 6 month cumulative rainfall totals were normal or above normal or higher across most all of England. The twelve month cumulative rainfall totals were above normal or higher totals in the majority of catchments. Most of the south coast and large parts of the north-west and central England have recorded notably or exceptionally high rainfall totals over the past 12 months, with England as a whole recording notably high cumulative rainfall. It is of interest to note that the 12 month cumulative rainfall total (October 2022 to September 2023) was the wettest since records began in 1891 for the River Bourne and the Upper Hampshire Avon in south-west England.

2. Soil moisture deficit

Soil moisture deficits (SMD) reduced across England during September as soils became wetter in many areas, due to above average rainfall.  There is a clear north-west to south-east divide, with wettest soils in the north-west and driest soils in the south-east.

Across most of England SMDs were below the LTA, leaving soils wetter than expected at the end of September. SMDs in the south-east are near or below LTA, meaning soils were drier than would be expected for the time of year.

3. River flows

September monthly mean river flows decreased at more than two-thirds of indicator sites we report on. The majority of sites were normal for the time of year, with more than a third of sites classed as above normal. Four sites, all in east or south-east England, were classed as below normal. The River Earmont and the River Weaver in the north-west as well as the River Tone in south-west England all had monthly mean river flows classed as notably high for the time of year.

Monthly mean river flows increased at all except 2 of the regional index sites in September, with Marston-on-Dove in central England on the River Dove and Horton on the Great Stour in south-east England seeing a decrease in flows which meant they were classed as normal and below normal respectively for the time of year. The Exe in south-west England, the Bedford Ouse in east England and the naturalised flows on the River Thames in the south-east, were all above normal for the time of year. The River Lune in north-west England recorded normal monthly mean river flows while Haydon Bridge on the River South Tyne in the north-east recorded notably high flows for September.

4. Groundwater levels

By the end of September, groundwater levels had decreased at all but 3 of the indicator sites we report on. More than two-thirds of groundwater sites were classed as normal for the time of year at the end of September. The remaining sites were all above normal or higher. Groundwater levels at Clanville Lodge Gate in the Test Chalk in south-east England remain notably high and levels in Skerne Magnesian Limestone at Aycliffe in north–east England and in the Dorset Stour Chalk at Woodyates in south-west England groundwater levels are above normal for the time of year. The West Cheshire Sandstone at Priors Heyes in north-west England continue to recover from the effects of historic abstraction and remains in the exceptionally high classification.

With the exception of 2 sites, Skirwith in the Carlisle Basin and Eden Valley Sandstone, and Little Bucket in the East Kent Stour Chalk, which were classed as notably high and above normal respectively, all the major aquifer index sites remained as normal for the time of year.

5. Reservoir storage

Reservoir storage during September declined at more than three-quarters of the reservoirs or reservoir groups we report on. At the end of September, nearly two-thirds reservoirs or reservoir groups are classed as normal.  Two reservoirs Hanningfield in east England and Bewl in south-east England recorded storage decreases of 11% and 10% respectively. The Teesdale group in north-east England recorded a 10% increase in storage. Five reservoirs were above normal and 3 were notably high at the end of September with the Lower Lee group in south-east England classed as exceptionally high for the time of year. In contrast, four sites remain below normal or lower, Colliford and Roadford in south-west England were below normal, Ardingly in south-east England was notably low as was the Dee System in Wales as a result on ongoing reservoir safety maintenance works expected to last until 2025.

At a regional scale, total reservoir storage in north-east and north-west England increased slightly at the end of September and decreased across the rest of England. For England as a whole, total reservoir storage decreased slightly to 81%.

6. Forward look

October began with a period of unseasonably warm weather, with settled conditions in many places. Towards the middle of the month conditions will become less settled, with wet weather expected to spread across England from the south-west. This trend of unsettled weather is expected to continue, with conditions generally being wetter than average. Temperatures are expected to remain slightly above average, with lower than expected chances of overnight frosts.

For the 3 month period for the UK from October to December there is a slightly higher than normal chance of the 3 month period being wetter than expected. There is a higher chance of conditions being mild than cold, although later in the period cold spells are still possible. Stormy spells are still likely, particularly near the end of the period.

7. Projections for river flows at key sites

By the end of March 2024, river flows are projected to be normal across most of England, although in the south-east, river flows have a greater likelihood of being above normal or higher. By the end of September 2024, river flows are projected to be above normal or higher in south-east, central and north-west England. In east and north-east England, river flows have a greater likelihood of being below normal or lower.

8. Projections for groundwater levels in key aquifers

By the end of March 2024, groundwater levels are projected to have a greater likelihood to be below normal or lower in parts of Lincolnshire and Yorkshire, while in south-west, north-west and east England groundwater levels have a greater likelihood of being above normal or higher. By the end of September 2024, groundwater levels in south-east and north-west England have a greater likelihood of being above normal or higher. In east, central and north-east England groundwater levels are projected to be below normal or lower.

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.