Research and analysis

Lincolnshire and Northamptonshire water situation: September 2025 summary

Updated 14 October 2025

Applies to England

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

1. Summary

September 2025 saw average to above average rainfall across Lincolnshire and Northamptonshire (LNA). Precipitation was above 50mm in each of the 6 hydrological areas, with totals ranging from 101% to 154% of the long term average (LTA). The Louth Grimsby and Ancholme and Witham to Chapel Hill hydrological catchments saw above average rainfall for September. As a result of the increased precipitation, in contrast to August 2025, the soil moisture deficit (SMD), averaged across Lincolnshire and Northamptonshire, reduced to 123.7mm, a reduction of 7.4mm compared to the beginning of the month.

River flows displayed a wide range of conditions across Lincolnshire and Northamptonshire, with flows ranging from 18% to 235% of the long term average. Six rivers were within the normal flow categorisation, while the Rase at Rase Bishopbridge and Welland at Ashley were notably high and above normal, respectively, and the 2 most easterly rivers, the Lud at Louth and Lymn at Partney, were noticeably low. Groundwater levels remained stable, and in most case, unchanged, recording either below normal or normal groundwater levels for this time of year.

Reservoirs continued to be drawn down and below target levels. The Trent-Witham-Ancholme transfer scheme operated throughout the majority of the month, while the Gwash-Glen transfer scheme and the Slea augmentation scheme were also in operation throughout September.

2. Rainfall

The 6 hydrological areas of LNA experienced between 51.4mm and 83.5mm of precipitation through September 2025, classified as normal or above for this time of year. LNA experienced 119% of its LTA precipitation for September.

September 2025 has been an outlier in terms of precipitation totals exceeding normal levels for the time of year as the past 3 to 12 months have been characterised by infrequent precipitation and dry weather. When considering the last 3 months, precipitation totals across LNA have ranged from 70% to 95% of the LTA, with 4 of the 6 hydrological areas receiving below average precipitation totals. This has predominantly been driven by August 2025 which contributed just 17mm to the 138mm total across the last three months.

The last 6-month period has been the tenth driest March to September across LNA since records began in 1891, with just 64% of the LTA precipitation (211mm). Exceptionally low precipitation totals have been recorded in Upper Welland and Nene, and notably low totals in 4 of the remaining 5 hydrological areas. Over the last year, LNA has received 78% of the LTA rainfall (501mm), with all hydrological areas recording notably low totals, apart from South Forty Foot and Hobhole which were below normal.

3. Soil moisture deficit and recharge

The average SMD across LNA decreased by 7.4mm through September to 123.7mm, as precipitation picked up, when compared to the start of the month. High rainfall events during the middle of the month had meant the SMD had reduced to 93.7mm by the 24 September, however a dry last week meant the deficit increased as the month concluded. There is an east-west split in SMD across the 6 hydrological areas, with the eastern areas having an SMD between 131mm and 160mm, and the western areas having an SMD between 101mm and 130mm. All 6 hydrological areas have an SMD that is 26mm to 50mm below the LTA, highlighting the dry weather experienced over the last 12 months.

4. River flows

River flows varied between 18% and 235% of their LTA during September 2025. Six rivers were within the normal flow categorisation, while the Rase at Rase Bishopbridge and Welland at Ashley were notably high and above normal, respectively, and the 2 most easterly rivers, the Lud at louth and Lymn at Partney, were noticeably low. This is an improvement in flows compared to August 2025 in which only 4 rivers were classified as having normal flow, while 5 had noticeably low flows and 2 had exceptionally low flows, for the time of year.

5. Groundwater levels   

Groundwater levels remained largely unchanged over the month of September. All sites recorded levels at below normal, except Aslackby and Barton which recorded normal groundwater levels for this time of year. Castlethorpe Bridge and Dunholme Road had no data for September 2025.

6. Reservoir stocks

Reservoir levels continue to be drawn down below their normal operating curves. Rutland is below Level 1, which is categorised as demand exceeding abstraction potential, however it remains above drought alert levels.

7. Environmental impact 

The Trent-Witham-Ancholme transfer scheme operated throughout the majority of September, while the Gwash-Glen transfer scheme and the Slea augmentation scheme were also in operation throughout the month.

8. Forward look

8.1 Probabilistic ensemble projections for river flows at key sites

December 2025: All flow sites are likely to experience below normal to notably low flows.

March 2026: All flow sites are likely to experience below normal flows; however, the likelihood of exceptionally low flows is greater than in December 2025.

8.2 Probabilistic ensemble projections for groundwater levels in key aquifers

March 2026: All groundwater sites, excluding Hanthorpe, are likely to experience below normal, or lower, groundwater levels, while Hanthorpe predictions are less conclusive.

September 2026: Groundwater level predictions for 12 months are less conclusive, but levels are likely to be below normal.

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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