Research and analysis

Solent and South Downs water situation report: December 2025 summary

Updated 14 January 2026

Applies to England

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

1. Summary

Solent and South Downs (SSD) had just over average rainfall in December, receiving 111% (115mm) of long term average (LTA) of 104mm. Monthly mean river flows for December ranged from normal to notably high across SSD. End of month groundwater levels for December ranged from normal to above normal. Soils across SSD ended the month wetter than the LTA for December. End of month reservoir stocks were below average at Ardingly Reservoir (Ouse) and at Arlington Reservoir (Cuckmere).

2. Rainfall

SSD had just over average rainfall in December, receiving 111% (115mm) of LTA (104mm). The Test Chalk and Lymington areal units received the highest monthly rainfall total with 130% of LTA. The Test Chalk unit received 121mm (LTA 93mm) while the Lymington unit received 137mm (LTA 105mm) during December. The Pevensey Levels areal unit received the lowest rainfall total with 79% (81mm) of LTA (103mm).

The highest daily rainfall total of 37mm was recorded on 18 December at Petersfield RG (Western Rother Greensand) and at Warnford RG (East Hampshire Chalk). However, this was part of a larger rainfall event that spanned 17 to 18 December. During these 2 days over 50mm was received on average across SSD and represented around 40% of the total monthly rainfall for December. There were 17 wet days during December, but 65% of the monthly rainfall fell over just 5 days (2, 5, 8, 17 and 18 December).

3. Soil moisture deficit and recharge

Soils across SSD ended the month on average for December.

4. River flows

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

Flows were normal on the:

• River Cuckmere at Cowbeech
• River Itchen at Allbrook and Highbridge
• River Medina at Blackwater
• River Meon at Mislingford
• River Test at Broadlands
• River Test at Chilbolton
• River Wallington at North Fareham

Flows were above normal on the:

• River Ouse at Goldbridge
• River Rother at Iping Mill

Flows were notably high on the:

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

The December monthly mean flows represent the fourth highest at Alfoldean (1970), sixth highest at Brockenhurst (1960) and eight highest at Sakeham (1967).

5. Groundwater levels 

End of month groundwater levels for December ranged from normal to above normal across SSD.

Groundwater levels were normal at:

• Chilgrove (West Sussex Chalk)
• Beeding Hill (West Sussex Chalk)
• Carisbrooke Castle (Isle of Wight)
• Catherington (East Hampshire Chalk)
• Clanville Gate (Test Chalk)
• Cornish Farm (East Sussex Chalk)
• Harting Common (Western Rother Greensand)
• Houndean Bottom (East Sussex Chalk)
• Lopcombe Corner (Test Chalk)
• West Meon (East Hampshire Chalk)
• Youngwoods Copse (Isle of Wight)

Groundwater levels were above normal at Preston Candover (East Hampshire Chalk).

6. Reservoir stocks

End of month reservoir stocks were below average for both Ardingly and Arlington Reservoirs. Ardingly Reservoir (Ouse) was at 76.5% of total capacity (LTA 87.0%) and Arlington Reservoir (Cuckmere) was at 76.3% of total capacity (LTA 87.0%).

7. Environmental impact 

7.1 Abstraction licence restriction

At the start of December there were 10 licence restrictions in force. By the end of the month 6 licence restrictions were in place. Over the month the restrictions included:

• one public water supply (PWS) licence on the Ouse under drought order conditions
• two licences (one PWS) on the River Meon,
• one licence on the River Hamble
• one licence on the Sowley Stream
• one PWS licence on the River Ems
• one licence on the Western Rother
• five licences on the Test
• one licence on the Itchen

7.2 Flood Alerts and Warnings in Force

There were 32 fluvial flood alerts issued in December. These were issued during 5 to 6 December (5), 8 to 9 December (5) and 18 to 19 December (22). Fourteen alerts were issued for rivers in Sussex and 18 for rivers in Hampshire and Isle of Wight (HIOW):

• Itchen, Rother (Sussex), Upper Ouse, Adur (east) and Cuckmere during 5 to 6 December
• Test, Itchen, Danes Stream, Eastern Yar and Aldingbourne Rife, and Barnham Rife during 8 to 9 December
• Bartley Water, Danes Stream, Lymington, Itchen, Test, Hamble, Meon, Gurnard Luck, Lukely Brook, Eastern Yar, Cuckmere, Ouse, Arun, Adur, Rother during 18 to 19 December

There were 13 fluvial flood warnings issued in December of which 5 were issued in Sussex and 8 issued in HIOW. The warnings were all issued on 18 to 19 December and were for:

• Bishops Waltham on the River Hamble
• Brockenhurst and Boldre on the River Lymington
• Chandlers Ford to Swaythling
• East Meon to Mislingford on the River Meon
• Landford to Wade Bridge on the River Blackwater
• Rushington and Eling on the Bartley Water
• Tilmore Brook through central Petersfield
• Carisbrooke and Hunny Hill on the Lukely Brook
• Barcombe Mills on the River Ouse
• Fittleworth on the Western River Rother
• Broadbridge Heath to Pallingham Quay on the River Arun
• Lodsbridge to Shopham Bridge on the Western River Rother
• Mock Bridge, near Shermanbury on the River Adur

Author: HydrologySSD@Environment-agency.gov.uk

Contact Details: 03708 506506

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.