Research and analysis

Water situation: April 2023 summary

Updated 11 January 2024

Applies to England

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

1. Water situation: April 2023

April was another wet month, with almost all catchments across England receiving above average rainfall. Soil moisture deficits remain low across England, with soils in many places wetter than would be expected for the time of year. River flows were normal or higher at almost all sites, although flows in many places decreased as they recovered from a wet March. Groundwater levels continued to increase at many sites, and almost all sites were classed as normal or higher for the time of year. Reservoir stocks at the end of April increased at almost half of the reservoirs and reservoir groups we report on, and three quarters of sites were classed as normal or higher for the time of year.

2. Rainfall

The April rainfall total for England was 63.9mm which represents 115% of the 1961 to 1990 long term average (LTA) for the time of year (114% of the 1991 to 2020 LTA). Except for fourteen catchments in the north west and north east, all catchments across England received above average rainfall during April. The wettest hydrological area was North Kent Chalk in south east England which received 186% of LTA rainfall during April. The driest hydrological area (relative to its LTA) was the Tweed catchment in north east England with 72% of LTA rainfall for the time of year.

April rainfall totals were classed as above normal or higher for the time of year in two thirds of catchments across England, including Dover Chalk in the south east which received exceptionally high rainfall during April. The remaining third of catchments were normal for the time of year. At the regional scale, south east, south west and east England all received above normal rainfall during April. Central, north east and north west England were normal for the time of year. April rainfall across England as a whole was normal for the time of year. The 2 month cumulative rainfall totals for March and April for England was the wettest since 1998.

The 3 month cumulative rainfall totals show that all catchments in England were classed as normal or higher, with a fifth notably high, mostly in the south east and east. The 6 month cumulative rainfall totals highlight how wet it has been with more than half of catchments being notably high or exceptionally high for the period. Twelve month cumulative rainfall totals were normal for more than half of catchments in England, although catchments in the south were generally above normal or higher, and in the far north some catchments were below normal.

3. Soil moisture deficit

Soil moisture deficits (SMD) remain low across England at the end of April following another month of above average rainfall across most of the country. Soils remain fully wetted across much of southern and western England. In east and north east England soil moisture deficits have grown slightly in those areas which saw lower rainfall totals during April.

April SMD values across the country remain lower than average for the time of year, meaning soils are wetter than would be expected. At a regional scale, the end of April SMDs are smaller than average for the time of year.

4. River flows

April monthly mean river flows increased at a third of indicator sites we report on, while the majority saw a decrease in monthly mean flows as rivers recovered from the very wet conditions during March. Despite these decreases, more than half of sites were above normal or higher for the time of year as flows remained higher than would be expected. A third of sites were normal for the time of year, while the River Burn at Burnham remained below normal.

Monthly mean river flows declined at all regional index sites during April, except the Great Stour at Horton in south east England which saw an increase in flows and ended April with notably high monthly mean river flows. Thorverton on the River Exe in the south west also saw notably high monthly mean river flows, while the Bedford Ouse in the east and naturalised flows on the River Thames in the south east were both above normal for the time of year. The River Dove in central England, South Tyne in the north east and River Lune in the north west were all normal for the time of year.

5. Groundwater levels

At the end of April, groundwater levels increased at three quarters of reported indicator sites as fully wetted soils and above average rainfall in much of the country allowed late spring recharge to continue in many aquifers. Almost all end of month groundwater levels were classed as normal or higher for the time of year. Three sites were below normal for the time of year.

The major aquifer index sites reflected a varied picture at the end of April, ranging from below normal to exceptionally high levels. Normal groundwater levels for the time of year were reported at Dalton Estate Well in the Hull and East Riding Chalk, at Redlands Hall in the Cam and Ely Ouse Chalk, at Skirwith in the Carlisle Basin and Eden Valley Sandstone, and at Jackaments Bottom in the Burford Jurassic Limestone. Despite groundwater levels increasing steadily, Stonor Park in the South West Chilterns Chalk remained at below normal levels for the time of year at the end of April. Little Bucket in the East Kent Stour Chalk and Weir Farm in the Bridgnorth Sandstone were both above normal for the time of year. Chilgrove in the Chichester Chalk was exceptionally high at the end of April after groundwater levels increased rapidly from normal levels the previous month.

6. Reservoir storage

Reservoir stocks at the end of April had increased at almost half of the reservoirs and reservoir groups we report on. A fifth had seen no change in stocks since March (as these were already full), and the remaining reservoirs and reservoir groups had seen a decrease in stocks. The largest stock increase was at Abberton Reservoir in east England which saw a 9% change. In contrast, Haweswater and Thirlmere in north west England saw a decrease of 8% in reservoir stocks. A quarter of reservoirs or reservoir groups were classed as below normal or notably low at the end of April. All other reservoirs or reservoir groups were classed as normal or higher for the time of year.

At a regional scale, total reservoir stocks ranged from 84% in south west England to 97% in south east England. Total reservoir stocks for England were 93% of total capacity at the end of April with little change since the end of March.

7. Forward look

May continued as April had ended with unsettled, wet conditions in many places, interspersed with sunny and warm periods. Moving towards the middle of the month more settled conditions are expected across much of the country, although showers are still expected. Wetter, unsettled conditions are expected in the north, while the south is likely to see brighter, dry weather with a risk of showers. Towards the end of May confidence in forecasts is low but unsettled, changeable conditions are expected to interrupt periods of dry and bright weather.

For the 3 month period for the UK from May to July there is an increased chance of warmer than normal and wetter than normal conditions. However, near average temperatures and rainfall remain the most likely outcomes. There is a higher than normal chance of heatwaves occurring, and there are likely to be notable differences in rainfall distribution due to the showery nature of summer rainfall.

8. Projections for river flows at key sites

By the end of September 2023, river flows have a greater likelihood of being above normal or high in south east, south west and central England, while other regions are most likely to see river flows in their expected normal range. By the end of March 2024 river flows in the south east, south west and east of England have a greater likelihood of being above normal or higher. In north west and central England there is a slightly higher chance of river flows being below normal or lower.

9. Projections for groundwater levels in key aquifers

By the end of September 2023 groundwater levels in south west, east and central England have a greater likelihood of being above normal of higher. Groundwater levels in the north east have a slightly higher chance of being below normal or lower. By the end of March 2024 groundwater levels have a greater likelihood of being above normal or higher in south east, east and central England. In south west and north west England groundwater levels are most likely to be in their expected range. In north east England there is a slightly higher chance of groundwater levels being below normal or lower.

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.