Research and analysis

East Anglia water situation: May 2025 summary

Updated 12 June 2025

Applies to England

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

1. Summary

Rainfall across East Anglia in May was below average, ranging from 31% to 78% of the long term average (LTA). With a dry start to the month, the soil moisture deficit (SMD) increased across the area, with a temporary decline at the end of May following rainfall. River flows continued to recede throughout May, with the majority of sites recording below normal or notably low flows for the time of year. Groundwater levels at all sites for which data was available have shown receding levels through April and May, with the majority of sites recording normal or below normal levels. All public water supply reservoirs are more than 90% of their full capacity.

2. Rainfall

May 2025 rainfall across East Anglia ranged from 31% to 78% of the LTA for the month. The month began dry, with rainfall occurring towards the end of the month. Northern catchments were typically slightly wetter than the catchments to the south-west and south-east. The East Anglia area average rainfall for May 2025 was 23mm, approximately 49% of the 1991 to 2020 LTA for May. Cumulative rainfall totals over the past 3 months, for all catchments in the East Anglia area have been classified as exceptionally low. The combined East Anglia rainfall for March to May was 51mm, which is the third driest spring rainfall total for East Anglia based on records going back to 1871. Over the past 12 months, rainfall totals have been classified as normal in the south-west catchments, with below normal and notably low classifications to the east of the area.

3. Soil moisture deficit and recharge

The SMD for East Anglia continued to increase into May 2025, with rainfall towards the end of the month reducing the deficit temporarily. The SMD across East Anglia ranged from 71mm to 130mm, with the west and south-east catchments experiencing the highest deficits. Across all catchments, the SMD difference from the LTA ranged from 26mm to 50mm.

4. River flows

River flows ranged between 28% to 79% of the LTA, with the majority of report sites recording below normal or notably low flows for the time of year. The lower flows were typically towards the centre and east of the area. One site, the Waveney, recorded exceptionally low flows, experiencing 28% of the LTA flow for the catchment. River flows declined throughout May, with increased flows towards the end of the month in response to rainfall.

5. Groundwater levels   

Groundwater levels at all sites for which data was available have shown receding levels through April and May. At the end of May groundwater levels across East Anglia area ranged from below normal to normal, with one site, Therfield recording notably high groundwater levels.

6. Reservoir stocks

By the end of May 2025, all reservoirs in the East Anglia area had more than 90% of their full capacity. Hanningfield, Alton, Ardleigh and Grafham all held water either on or below their respective operating curves. Abberton’s stored volume was above the normal operating curve.

7. Forward look

7.1 Probabilistic ensemble projections for river flows at key sites

River flow projections show a high probability of normal or below normal flows by the end of June 2025 for the:

• Ouse
• Kym
• Ivel
• Bedford Ouse

River flow projections for the Ely Ouse show a higher probability of exceptionally low flows. For September 2025, flow projections indicate an approximate 48% or higher probability of normal or higher flows for the Ouse, Kym, Ivel and Bedford Ouse. The Ely Ouse projection for September 2025 indicates a 44% probability of below normal flows.

7.2 Probabilistic ensemble projections for groundwater levels in key aquifers

Groundwater level projections show a high probability of below normal to normal groundwater levels by the end of September 2025. The Therfield Rectory projection indicates levels will remain above normal to notably high. Groundwater level projection for March 2026, show a high probability of notably low to below normal groundwater levels. The Therfield Rectory projection indicates an approximate 55% or higher probability of normal or higher groundwater levels by the end of March 2026.

Author: Hydrology Team, hydrology-ean-and-lna@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.