Research and analysis

Lincolnshire and Northamptonshire water situation: May 2025 summary

Updated 12 June 2025

Applies to England

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

1. Summary

Following a dry start to spring, May continued with lower than average rainfall across the Lincolnshire and Northamptonshire area (LNA), with totals ranging from 44% to 92% of the long term average (LTA). Rainfall classifications varied across the 6 hydrological areas, with:

• normal totals recorded in the Lower Welland and Nene and South Forty Foot and Hobhole
• notably low totals in the Upper Welland and Nene

Soil moisture deficits (SMD) continued to increase in line with seasonal trends throughout May, although all sites moved from exceptionally high in April to notably high by the end of the month following heavy rain at the end of May.

Groundwater levels at most sites remained stable compared to April, with the exception of Burnham which dropped from normal to below normal. River flow classifications remained largely unchanged since April, with some variation across the region. Notably, Langworth (Barlings Eau) recorded exceptionally low flows for the time of year.

Most reservoirs ended the month slightly below their normal operational curves. The Trent-Witham-Ancholme transfer scheme was operational throughout June, supplying water to both the Witham and Ancholme rivers.

2. Rainfall

Rainfall across LNA was below average in May 2025, with just 31mm recorded (63% of the LTA). Conditions varied by catchment – South Forty Foot and Lower Welland and Nene saw near normal totals, but Upper Welland and Nene remained notably low. The month was dry overall, with most rainfall arriving late.

Spring (March to May) has been particularly dry, with all catchments classified as having exceptionally or notably low rainfall. The regional total of 61mm makes it the seventh driest spring on record (since 1871), and even more severe locally: the fifth driest for Upper Welland and Nene and Witham to Chapel Hill, and the fourth driest for Louth Grimsby and Ancholme.

Over the past 12 months, rainfall has been normal in most catchments, but Louth Grimsby and Ancholme now shows a below normal annual total.

3. Soil moisture deficit and recharge

SMD rose sharply across all catchments during May, consistent with the dry start to the month. Rainfall towards the end of May caused a brief reduction in SMD, but this was temporary, and deficits then continued to rise. On average, SMD increased from 67mm in late April to 108mm by the end of May, placing it in the notably high category for the time of year.

4. River flows

Monthly mean river flows ranged from 23% to 74% of their LTA. Five of the 10 sites we report on were classified as normal (mostly in the south of the area), while the remaining 5 ranged from below normal to exceptionally low for the time of year. Most sites maintained the same classification as in April.

However, Barrowden/Tixover declined from below normal to notably low, Wansford normal to below normal, and Langworth (Barlings Eau) notably low to exceptionally low. In contrast, the monthly average flow at Rase Bishopbridge increased from below normal to normal, responding to rainfall at the end of the month.

5. Groundwater levels   

Following below normal rainfall across LNA in April, groundwater level trends continued to decline at all indicator sites, consistent with seasonal expectations. However, banding remained unchanged at all monitored sites compared to the previous month, except for the Chalk at Burnham, which shifted from normal into the below normal classification.

6. Reservoir stocks

Reservoir stocks across the area remained generally healthy at the end of May. Pitsford ended the month above its normal operating curve, while Rutland, Ravensthorpe, Hollowell and Covenham were all below their normal operating curves, but comfortably above drought alert levels.

7. Environmental impact 

The Trent-Witham-Ancholme (TWA) transfer scheme was operating through June, transferring water from both the Witham to the Ancholme and the Trent to the Witham. The Slea Augmentation and Gwash to Glen transfer schemes remained off. During May there were 10 hands off flows active:

• 2 in the Ancholme catchment
• 4 in the Witham catchment
• 2 in the Nene
• 2in the Steeping catchment

There was no flood alerts or warnings issued during May in the Lincolnshire and Northamptonshire area.

8. Forward look

8.1 Probabilistic ensemble projections for river flows at key sites

June 2025: There is an increased probability of less than normal flows on the Nene, reflecting the continued dry conditions and limited recent rainfall. North Brook is showing an increased chance of normal flows.

September 2025: While the probability pie charts indicate a wide range of potential outcomes, the projections are statistically inconclusive.

8.2 Probabilistic ensemble projections for groundwater levels in key aquifers

September 2025: Grainsby is showing a greatly increased probability of normal levels. Horkstow is suggesting a greatly increased chance of below normal levels. There is no forecast for Hanthorpe.

March 2026: Both Grainsby and Horkstow are showing an increased probability of below normal groundwater levels. There is no forecast for Hanthorpe.

Author: Pan 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

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