Research and analysis

Water situation: December 2022 summary

Updated 11 January 2023

Applies to England

Monthly rainfall totals in December were in the normal range in most catchments across England. Soil moisture deficits continue to decline and at the end of the month and deficits across most of England were typical for this time of year. River flows decreased at nearly two thirds of indicator sites in December and the majority of sites were classed as normal or higher for the time of year. Groundwater levels increased at most indicator sites, and almost half were classed as normal for the time of year. Reservoir stocks in December increased at all except one of the reservoir and reservoir groups we report on, although nearly half of reservoirs were still classed as below normal or lower for the time of year.

1. Rainfall

The December rainfall total for England was 89.3mm which represents 106% of the 1961 to 1990 long term average (LTA) for the time of year (97% of the 1991 to 2020 LTA). At the regional scale above average rainfall fell in December with the exception of central and eastern England which saw below average rainfall. Most catchments received above average rainfall during December. The wettest hydrological area was the Dover Chalk in southeast England which received 167% of December’s LTA rainfall. The driest area was the middle Severn in central England with 67% of LTA rainfall for December.

December rainfall totals were classed as normal or higher for almost all catchments across the country, with only two catchments classed as below normal for the time of year. At a regional scale, December rainfall totals were classed as normal in all regions of the country and for England as a whole.

December was the fourth consecutive month of above average rainfall for England as a whole. The 3 month cumulative totals in almost all catchments being above normal or higher. The 6 month cumulative rainfall totals were classed as normal for most of the country. The 12 month cumulative rainfall totals were classed as normal or lower in all catchments across England with cumulative rainfall in Norfolk catchments being classed as notably or exceptionally low.

2. Soil moisture deficit

Soil moisture deficits (SMD) continued to reduce across England during December. Soils, as expected for the time of year, became wetter in many areas due to the rainfall in the second half of the month.

End of December SMD values across the majority of the country were generally close to or smaller than the LTA for the time of year. At a regional scale, the end of December SMD for most regions were typical for the time of year.

3. River flows

December monthly mean river flows decreased at nearly two thirds of the indicator sites we report on since November. Two thirds of sites were normal for the time of year, with a fifth above normal for the time of year. Eight sites were below normal or lower for the time of year.

All the regional index sites monthly mean flows were classed as normal except for Marston-on-Dove on the River Dove in central England which was below normal for the time of the year. Flows on the River Exe at Thorverton in south west England and the Great Stour at Horton in south east England decreased to be classed as normal having been above normal and notably high respectively in November.

4. Groundwater levels

At the end of December, groundwater levels increased at all but five of the reported indicator sites as wet soils and further rainfall helped most aquifers continue their seasonal recharge. Almost half of the end of month groundwater levels were classed as normal for the time of year. The remaining sites were split, with seven sites above normal, while the remaining seven sites were below normal for the time of year.

The major aquifer index sites showed a varied picture at the end of December. Index sites in the major aquifers were classed as normal at most sites. Index site classifications range from notably high at Chilgrove in the Chichester Chalk in the south Downs, where groundwater levels increased throughout December. In contrast Skirwith in the Carlisle Basin Sandstone and Stonor Park in the South West Chilterns Chalk both remained at below normal levels at the end of December.

5. Reservoir storage

At the end of December reservoirs stocks had increased at all except one of the reservoirs and reservoir groups we report on. Five reservoirs or reservoir groups saw an increase of more than 20% in their stocks in comparison to the end of November. The largest stock increases were at Clatworthy and Wimbleball in the southwest England which increased by 45% and 31% respectively. Despite these increases, nearly half of all reservoirs or reservoir groups were classed as below normal or lower for the time of year. The Dee reservoirs which supply northwest England are undergoing reservoir safety work.

At the regional scale, total reservoir stocks ranged from 61% in south-west England to 89% in north-east England. Total reservoir stocks for England were at 82% of total capacity at the end of December.

6. Forward look

Early January was dominated by changeable conditions for many with wet and windy weather mixed with sunny spells. Unsettled conditions are forecast to persist during much of January until the end of the month brings more settled conditions. Temperatures are forecast to be occasionally mild but generally around average.

For the three month period from January to March there is an increased chance of mild conditions. There is an increased likelihood of heavy rain and strong winds compared to the early winter, and there is a slight increase in the period as a whole being wet.

7. Projections for river flows at key sites

By the end of March 2023 and September 2023 river flows have a greater likelihood of being above normal across most of England. In central and north west England river flows have a greater chance of being normal. By the end of September 2023 river flows have an increased chance of being above normal in all regions except in the central and north western areas where river flows are most likely to be normal.

8. Projections for groundwater levels in key aquifers

By the end of March 2023 groundwater levels have a higher than expected chance of being normal or lower in all regions except south west and central England, where groundwater levels have an increased likelihood of being above normal or higher. By the end of September 2023 groundwater levels have a higher than expected chance of being above normal or higher in east and central England. In north west and north east England there is a higher than expected chance of groundwater levels being below normal or lower. Groundwater levels in the south west and south east have a higher than expected chance of being normal by the end of September 2023.

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

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.