1. Summary

Solent and South Downs (SSD) had above average rainfall in January, receiving 146% (127mm) of the long term average (LTA, 87.3mm). Monthly mean river flows across SSD ranged from normal to notably high and the end of month groundwater levels ranged from normal to exceptionally high. Soils across SSD ended the month wetter than the average for January. End of month reservoir stock was above average at Ardingly Reservoir (Ouse) and was below average at Arlington Reservoir (Cuckmere).

2. Rainfall

SSD had above average rainfall in January, receiving 146% (127mm) of the LTA (87.3mm). The areal units in Hampshire received higher rainfall than those in Sussex. The Test Chalk areal unit in the west of SSD received the highest rainfall with 163% (139mm) of the LTA (84.4mm). While the Pevensey Levels areal unit on the eastern coast received the lowest rainfall with 125% (103mm) of the LTA (82.2mm).

The New Year started very wet, about 50% of the month’s rainfall fell between 1 and 8 January. The wettest day of the month was 4 January, when over 20% of the month’s rainfall fell in one day, also the SSD highest daily rainfall totals of January were recorded on this day, with:

• 41.3mm at Duncton RG (Western Rother Greensand)
• 40.0mm at Chilgrove House RG (West Sussex Chalk)
• 37.8mm at Walderton RG (West Sussex Chalk)

The middle of the month, between 9 and 20 January, was mostly dry for 12 consecutive days.

The other half of the month’s rainfall fell between 21 and 31 January. During this period, the first named storm of 2025, Storm Éowyn, hit the UK between 23 and 24 January. While the main impacts from the storm were due to the wind, it also brought some very wet weather, with high daily rainfall totals on 26 January, receiving:

• 37.6mm at Testwood TBR (Hampshire Tertiaries)
• 36.3mm at Broughton RG (Test Chalk)

The last 12 months (February to January) has been the fifth wettest on record for SSD. The Test Chalk areal unit recorded their second wettest, and the East Sussex Chalk units its fourth wettest 12-month period. All the SSD areal units recorded rainfall in the top 10 wettest on record in the last 12 months.

Over the longer time periods, 18-month and 24-month running totals remain exceptionally high and were the wettest on record for SSD. These periods were also the wettest for: Test Chalk, East Hampshire Chalk, Isle of Wight, Hampshire Tertiaries and Lymington areal units.

All these statistics are based on records going back to 1871.

3. Soil moisture deficit and recharge

Soils across SSD ended the month wetter (0mm) than the LTA for January (1mm).

4. River flows

Monthly mean river flows across SSD ranged from normal to notably high.

Flows were normal on the:

• River Meon at Mislingford
• River Wallington at North Fareham
• River Medina at Blackwater

Flows were above normal on the:

• River Test at Chilbolton
• River Test at Broadlands
• River Itchen at Allbrook and Highbridge
• River Rother at Iping Mill
• River Ouse at Goldbridge
• River Cuckmere at Cowbeech

Flows were notably high on the:

• River Lymington at Brockenhurst
• River Arun at Alfoldean
• River Adur at Sakeham

The monthly mean flows for January were the seventh highest on record for the River Arun at Alfoldean (1970) and River Adur at Sakeham (1967). Also, for the River Test at Chilbolton (1989) and the River Lymington at Brockenhurst (1960), the monthly mean flows were the 10th highest on record.

5. Groundwater levels 

End of month groundwater levels for January ranged from normal to exceptionally high.

Groundwater levels were normal at:

• Catherington (East Hampshire Chalk)
• Harting Common (Western Rother Greensand)
• Chilgrove (West Sussex Chalk)
• Beeding Hill (West Sussex Chalk)
• Houndean Bottom (East Sussex Chalk)

Groundwater levels were above normal at:

• Carisbrooke Castle (Isle of Wight)
• West Meon (East Hampshire Chalk)
• Cornish Farm (East Sussex Chalk)

Groundwater levels were notably high at:

• Clanville Gate (Test Chalk)
• Lopcombe Corner (Test Chalk)
• Youngwoods Copse (Isle of Wight)

Groundwater levels were exceptionally high at:

• Preston Candover (East Hampshire Chalk)

The exceptionally high groundwater levels for January were the fourth highest at Preston Candover (1975). The notably high levels for January were the fifth highest at Youngwoods Copse (1978), and sixth highest at Clanville Gate (1966).

6. Reservoir stocks

End of month reservoir stocks were above average at Ardingly Reservoir (Ouse) and were below average at Arlington Reservoir (Cuckmere). Ardingly Reservoir (Ouse) was at 100% of total capacity (LTA 93%), and Arlington Reservoir (Cuckmere) was at 82.6% of total capacity (LTA 95.4%).

7. Environmental impact 

Abstraction licence restrictions:

During January there were a total of 2 licence restrictions in force, one cessation and one reduced abstraction rate. The cessation was in force on the River Lymington (New Forest) and the reduced abstraction rate restriction was in force on the River Meon (East Hampshire).

7.1 Flood Alerts

During January there were 42 fluvial flood alerts issued in the SSD area, there were:

• 15 in Hampshire
• 4 in the Isle of Wight
• 23 in Sussex

Also, there were 4 groundwater flood alerts issued in the SSD area, all in Hampshire.

7.2 Flood Warnings

During January there were 15 fluvial flood warnings issued in the SSD area, there were:

• 5 in Hampshire
• 1 on the Isle of Wight
• 9 in Sussex

Author: HydrologySSD@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.