Lincolnshire and Northamptonshire water situation: September 2024 summary
Updated 11 October 2024
Applies to England
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Following a notably dry August, September saw significantly wetter conditions with exceptionally high rainfall across Lincolnshire and Northamptonshire. Totals ranged from 173% to 346% of the long-term average (LTA), classifying the rainfall as notably high to exceptionally high across the 6 hydrological areas. This made it the second-wettest September on record for the region. The southern part of the region received more rainfall than the north, making it the wettest September on record for the Upper Welland and Nene hydrological area. As a result of the exceptionally high rainfall, soil moisture deficits (SMD) decreased significantly across the region, particularly in the south. River flows increased dramatically, most notably in the Welland and Nene areas, where all indicator sites recorded record-high monthly mean flows for September. Groundwater levels remained high and are expected to continue increasing in October due to the heavy rainfall seen at the end of September. Reservoir stocks have mostly risen across the area. Lastly, all transfer schemes were off by the end of the month and are likely to remain off for the foreseeable future.
1. Rainfall
After a notably dry August, September brought an average of 123mm of rainfall across the area. Rainfall ranged from 173% to 346% of the LTA, classifying it as notably high to exceptionally high for the time of year. There was a north-south divide, with southern areas receiving more rainfall than those in the north, and the highest rainfall occurring towards the end of the month. This made it the second-wettest September on record (dating back to 1871) for the region overall, and the wettest ever for the Upper Welland and Nene area, surpassing previous records by over 40mm. The three-month and six-month trends display normal to exceptionally high rainfall totals, with the highest values seen in the south. The Water Year 2023/2024 has been the wettest since 1882/1883, largely due to last winter’s wet conditions; as a result, the 12-month trend continues to display its exceptionally high totals.
2. Soil moisture deficit and recharge
Due to the exceptionally wet September, SMD decreased significantly and ended the month at below normal to exceptionally low levels for the time of year. The highest levels of SMD were observed in the northern areas, as a result of the lower rainfall totals. SMD remained above normal for most of September before dropping sharply at the end of the month, following the week of heavy rainfall. Cooler autumn temperatures will have further contributed to this decline in SMD. The area as a whole ended the month with an SMD of 35mm, in comparison to 120mm at the end of August.
3. River flows
The exceptionally high rainfall totals caused river flows to increase at all indicator sites, with the largest rises observed in the southern region, particularly the Wellend and Nene catchments. Monthly mean flows ranged from 62% to 1570% of the LTA, classifying river flows as normal to exceptionally high across the area. Record-breaking monthly mean flows for September were recorded at several sites, including Ashley (Welland), Barrowden/Tixover (Wellend), Geldharts Mill (Nene), Upton Mill (Nene) and Wansford (Nene).
4. Groundwater levels
Despite the exceptionally high levels of rainfall, most groundwater indicator sites saw levels decline through September. This is likely because the heaviest rainfall occurred late in the month, with its full impact expected to be seen in October. By the end of September, groundwater levels were classified as normal to exceptionally high for the time of year, with the highest levels being recorded at Hanthorpe, the most southernmost groundwater indicator site.
5. Reservoir stocks
Reservoir stocks across the area mostly increased during September following the exceptionally high rainfall. Both Pitsford and Ravensthorpe and Hollowell combined saw sharp increases and ended the month significantly above their operational targets. Rutland and Covenham remained slightly below target but are expected to rise in the coming weeks due to the high river flows.
6. Environmental impact
The Trent-Witham-Ancholme transfer scheme operated for most of September, transferring water from the River Trent to River Witham and River Witham to River Ancholme. However, given the end of month rainfall totals, the Trent-Witham and Witham-Ancholme transfers were turned off on 25 September and 28 September, respectively. The Gwash-Glen and Slea Augmentation schemes remained off throughout September. It is unlikely any transfer schemes will be required for the remainder of the operational year. No cessation notices were issued during September. There were eight flood alerts and 14 flood warnings issued.
7. Forward look
7.1 Probabilistic ensemble projections for river flows at key sites
December 2024: All sites are showing a greatly increased probability of greater than normal flows.
March 2025: Both Nene-Northampton and Nene-Wansford are showing an increased probability of greater than normal flows. North Brook is showing a slightly increased probability of below normal flows.
7.2 Probabilistic ensemble projections for groundwater levels in key aquifers
March 2025: All sites are showing a greatly increased probability of exceptionally high 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
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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