1. Summary

In December, the Lincolnshire and Northamptonshire area received an average total rainfall of 67mm, which was 120% of the long-term average (LTA). On average, rainfall totals for the area as a whole were classified as normal for the time of year. This marks the third consecutive month with normal rainfall levels. Soil moisture deficits (SMD) decreased in all hydrological areas except the Lower Welland and Nene, where levels slightly increased toward the end of the month. By the end of December, the area had an SMD of 4mm, which remains within the below normal category for this time of year. River flows at most sites responded in line with the rainfall received across December. Monthly mean river flows ranged from 137% to 259% of the LTA, falling within the above normal to notably high classifications. Following the normal levels of rainfall and below normal SMD across the area in December, groundwater levels remained normal or higher at all sites with available data. With the exception of Covenham, reservoirs in the area ended the month above their normal operating curves.

2.  Rainfall

In December, the Lincolnshire and Northamptonshire area received an averaged total rainfall of 67mm, which was 120% of the LTA. Rainfall was distributed throughout the month, but 6 days (4, 5, 7, 8, 18 and 31 December), accounted for approximately 87% of the month’s total rainfall. 18 December was the wettest day of the month, with an average of 18mm rainfall across the 6 catchments. 

On 7 December 2024, a deep Atlantic low-pressure system named Storm Darragh brought significant rainfall. Totals included 22mm recorded in Steeping Great Eau and Long Eau, 18mm in Louth Grimsby and Ancholme, and an average of 14mm rainfall across the 6 catchments, making it the second wettest day in December 2024. A south-north trend in rainfall distribution was evident, with northern areas receiving slightly higher rainfall than the south.

On average, rainfall totals received for the area as a whole was classified as normal for the time of year. This marks the third consecutive month with normal rainfall levels. Rainfall across the hydrological areas ranged from 58mm to 79mm (102% to 135% of the LTA), resulting in classifications of normal to above normal rainfall for the time of year. Although the 3-month map displays all 6 hydrological areas classified as normal, a north-south trend pattern is reflected in all the long-term rainfall maps, which unanimously shows the higher totals received in the south compared to the north.

3. Soil moisture deficit and recharge

SMD decreased in all hydrological areas except the Lower Welland and Nene where the levels slightly increased towards the end of the month. The lowest levels of SMD were observed in the Upper Welland and Nene (2.7mm), whilst the highest levels were observed in the Ancholme Grimsby Louth (6.3mm). On average, SMD for the area decreased from 13mm at the end of November to 4mm by the end of December. Despite this reduction, the overall figure remains within the below normal range for the time of year.

The SMD difference-to-LTA (mm) map show most hydrological areas are in the -25mm to -6mm category, indicating that they are slightly wetter than normal for the time of year. The only exception is the Lower Welland and Nene hydrological area that is in the -50mm to -26mm category, meaning it is significantly wetter than normal.

4. River flows

Mean monthly flows ranged from 137% to 259% of the LTA, and from above normal to notably high classification. At most sites, river flow responded in line with the amount of rainfall received in December. River flow sites in the north of the area changed banding from normal levels in November to above normal and notably high classification in December. Flow sites in the south of the area did not change banding since November 2024, except Geldharts Mill (Nene) which changed banding from notably high to above normal classification.

5. Groundwater levels   

Following the normal levels of rainfall and below normal SMD across the area in December, groundwater levels remained normal or higher at all sites with data. Except Grange de Lings, the groundwater level trends showed a slight increase at all monitoring sites with data. Grange de lings decreased from above normal to normal level classification.

6. Reservoir stocks

With the exception of Covenham, reservoirs in the area ended the month above their normal operating curves. The level at Covenham was 15% below target in November, however levels are not alarmingly low.

7. Environmental impact 

During December, there were 18 flood alerts, and 4 flood warnings issued. All transfer schemes remained off throughout December. No licence cessations were issued.

8. Forward look

8.1 Probabilistic ensemble projections for river flows at key sites

March 2025: All sites are showing slightly increased probabilities of greater than normal flows with none of the modelled rainfall scenarios showing exceptionally low level.

June 2025: The two Nene sites are showing increased probabilities of normal flows. North Brook is showing a reduced probability of extreme flows (both high and low).

8.2 Probabilistic ensemble projections for groundwater levels in key aquifers

March 2025: All sites are showing an increased probability of groundwater levels being normal or higher with none of the modelled rainfall scenarios showing exceptionally low levels.

September 2025: All sites are showing a reduced probability of exceptionally low levels.

Author: Pan Hydrology Team, Hydrology-EAN-and-LNA@environment-agency.gov.uk

Contact details: 03708 506 506

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