Research and analysis

Water situation: December 2023 summary

Updated 11 January 2024

Applies to England

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

It was the wettest December since 2012 with rainfall totals well above normal across England, with all catchments receiving above average rainfall. Soil moisture deficits (SMD) reduced across England during December as soils became saturated due to the above average rainfall. River flows increased at more than three-quarters of the sites we report on, with the majority of sites exceptionally high for the time of year. Groundwater levels increased at four-fifths of the sites we report on, with all groundwater levels classed as normal or higher for the time of year. Reservoir stocks increased at three-quarters of the reservoirs or reservoir groups we report on, with almost two-thirds of reservoirs classed as above normal or higher for the time of year.  

1. Rainfall 

The December rainfall total for England was 145mm which represents 172% of the 1961 to 1990 long term average (LTA) for the time of year (158% of the 1991 to 2020 LTA). All catchments throughout the country received above average rainfall during December. The wettest hydrological area relative to the LTA was the Witham and Chapel Hill catchment in east England, which received 219% of LTA rainfall. The driest hydrological area was South London in south-east England which received 124% of LTA rainfall in October. 

December rainfall totals were classed as above normal or higher for the time of year in the majority of the hydrological areas across England with only 3 areas classed as normal. The majority of hydrological areas, predominately in the northern, central and south-western areas of the country, were classed as receiving notably or exceptionally high rainfall for the time of year. Over a quarter of hydrological areas, spread mainly across east and south-east England reported above normal rainfall during the month. Rainfall totals at a regional scale during December, was classed as exceptionally high at central, north-west, and north-east England. December rainfall was notably high at east and south-west England and above normal in the south-east. December’s rainfall total for England as whole was notably high. 

The 3-month cumulative rainfall totals for all but 2 hydrological areas throughout the country were classified as either notably high or exceptionally high. Over three-quarters of hydrological areas recorded rainfall totals classed as exceptionally high for this period. The 6-month cumulative rainfall totals show a similar picture, with rainfall classed as above normal or higher across all hydrological areas in England with over four-fifths classed as exceptionally high. Both the 3 and 6 month cumulative totals to December were the third wettest for England since records began in 1871 and the wettest since 2000. Thirteen hydrological areas had their wettest second half to the year on record (since 1871). The 12-month cumulative rainfall totals were exceptionally high in nearly two-thirds of hydrological areas across England. Seven hydrological areas predominately across central southern England, the Avon Dart and Erme, the River Bourne, the Isle of Wight, the River Test, the Upper Hampshire Avon, the Mid Hampshire Avon and the Berkshire Downs, had their wettest year on record (since 1871). The remaining hydrological areas were either above normal or notably high with only one catchment classed as normal, the Esk (Dumfries) in north-west England. 

2. Soil moisture deficit  

SMD continued to decrease throughout England during December, as soils throughout the country became saturated in response to the above average rainfall during December. Soil moisture deficits across the south-east and east England experienced the greatest decreases during December. 

Across all of England, SMDs were below the LTA, leaving soils wetter than expected at the end of December. Soils across most of England were at saturation levels. 

3. River flows 

December monthly mean river flows increased at more than three-quarters of indicator sites we report on compared to the previous month. All sites were classed as above normal or higher flows for the time of year. The majority of sites were classed as exceptionally high predominantly across northern and central England. The highest monthly mean December flows on record were recorded on the:

• River Derwent at Derby St Marys (record since 1970)
• River Trent at North Muskham (record since 1969)
• River Till at Heaton Mill (record since 2001)
• River Mersey at Ashton Weir (record since 1976)
• River Weaver at Ashbrook (record since 1977)
• River Frome at East Stoke (record since 1965)

Over a third of sites, mainly in south-west and south-east England were classed as above normal. 

Monthly mean river flows increased at all but two of the regional index sites in December compared to November. Flows increased at Marston-on-Dove in central England on the River Dove and are classed exceptionally high. Flows at Haydon Bridge on the River South Tyne, Carlton on the River Lune and the naturalised flows at Kingston on the River Thames increased to be classed as notably high for the time of year. Flows also increased at Offord on the Bedford Ouse which was classed as above normal. Flows decreased at Horton on the Great Stour in south-east England, and Thorverton on the Exe in south-west England and monthly flows for both sites are classed as above normal for the time of year. 

4. Groundwater levels   

By the end of December, groundwater levels had increased at over four-fifths of indicator sites we report on, with all groundwater sites classed as normal or higher by the end of December. Two-thirds of indicator sites, mainly in the central, east and north-east England, were classed as exceptionally high. The highest ever groundwater levels for December were recorded at Hanthorpe (Lincolnshire Limestone) in east England (record since 1972) and Coxmoor (Idle Torne Nottinghamshire & Doncaster Permo Triassic Sandstone) in central England (record since 1990). Priors Heyes in north-west England continued to experience the exceptionally high groundwater levels, as the West Cheshire Sandstone continues to recover from the effects of historic abstraction. 

Groundwater levels at the end of December increased at all major aquifer index sites. Dalton Estate in the Hull and East Riding Chalk and Skirwith in the Carlisle Basin Sandstone were classed as exceptionally high and Chilgrove in the Chichester Chalk, and Little Bucket in the Stour chalk were classed as notably high. Stonor Park in the South West Chilterns chalk and Jackaments Bottom in the Burford Jurassic Limestone reported above normal and normal groundwater levels respectively. 

5. Reservoir storage  

Reservoir storage during December increased at over three-quarters of the reservoirs or reservoir groups we report on. By the end of December storage at almost two-thirds of reservoirs or reservoir groups was classed as above normal or higher. Eight reservoirs recorded storage increases greater than 10% with Ardingly in south-east England recording the largest increase of 24%. Refill at some reservoirs has been impacted by high turbidity levels for example at Farmoor in south east England. Planned operational work at Bewl Water is impacting reservoir levels there. The Dee System in Wales remains notably low due to ongoing reservoir maintenance. 

At a regional scale, total reservoir storage increased across all of England by the end of December, with the south-west of England reporting the largest increase of 8%. For England as a whole, reservoir storage has increased by 5% to a total of 92%. 

6. Forward look 

January started with very wet conditions across England. This wet weather will be followed by a more settled, cold period moving into the middle of the month. There will still be a chance of showers, although they may fall as snow with ongoing cold conditions. Towards the end of the month unsettled conditions are likely to return from the west, bringing rain and possibly snow with ongoing cold conditions.  

For the 3-month period for the UK from January to March, there is a slightly higher than normal chance of cold conditions bringing with it an increased chance of impacts from ice, fog and snow. The period is unlikely to be wet, with precipitation likely to be around average for the time of year. It is also likely to be calm, with a low chance of a windy season.  

7. Projections for river flows at key sites 

By the end of March 2024, river flows in the south-east, south-west, east and central England have a higher than expected chance of being above normal or higher. This is particularly true for those in groundwater fed catchments where groundwater levels are currently higher than expected for the time of year and can support river flows over the next 3 months.  

By the end of September 2024, rivers across most of England have the greatest chance of being above normal or higher, except in the north-west where flows are more likely to be normal.  

8. Projections for groundwater levels in key aquifers 

By the end of March 2024, groundwater levels in the east, south-east and north-east England have a greater likelihood of being above normal or higher. Sites in chalk aquifers are likely to be notably high or higher. In south-west, north-west and central England groundwater levels have a greater likelihood of being normal or higher. 

By the end of September 2024, groundwater levels have a greater likelihood of being above normal or higher in north-west, north-east, south-east and east England. In south-west and central England, groundwater levels have a greater likelihood of being normal or higher.  

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.