Research and analysis

Solent and South Downs water situation report: August 2025 summary

Updated 12 September 2025

Applies to England

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

1. Summary

Solent and South Downs (SSD) had below average rainfall in August, receiving 61% (41mm) of the long term average (LTA) of 66mm. Monthly mean river flows across SSD ranged from notably low to normal. The end of month groundwater levels ranged from exceptionally low to above normal. Soils across SSD ended the month drier than the average for August. End of month reservoir stocks were below average at Ardingly Reservoir (Ouse) and at Arlington Reservoir (Cuckmere).

2. Rainfall

SSD had below average rainfall in August, receiving 61% (41mm) of LTA (66mm). The Sussex Coast areal unit received the highest rainfall during August with 85% (50mm) of LTA (59.3mm). The Pevensey Levels areal unit received the lowest rainfall with 32% (21mm) of LTA (64.6mm). 

Most of August was dry until the 26 August when heavy rainfall occurred. The 28 August was the wettest day with some very high totals due to thunderstorms. The highest daily totals were recorded on 28 August at Westergate (Sussex Coast) and Calbourne (Isle of Wight) received with 59.8mm and 56.9mm respectively.

The last 6 months has been the sixth driest March to August period on record for SSD. It was the fourth driest March to August period on record for the Test Chalk areal unit. Only the March to August periods for 1976,1921 and 1990 were drier. For the Hampshire Tertiaries areal unit was the fifth driest March to August period.

For the 24-month period (starting September 2023) it was the seventh highest total for SSD.

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

3. Soil moisture deficit and recharge

Soils across SSD ended the month drier than the LTA for August.

4. River flows

Monthly mean river flows for August ranged from notably low to normal across SSD.

Flows were notably low on the:

• River Lymington at Brockenhurst
• River Meon at Mislingford

Flows were below normal on the:

• River Arun at Alfoldean
• River Test at Broadlands
• River Test at Chilbolton

Flows were normal on the:

• River Test at Chilbolton
• River Itchen at Allbrook and Highbridge
• River Wallington at North Fareham
• River Medina at Blackwater
• River Rother at Iping Mill
• River Cuckmere at Cowbeech
• River Adur at Sakeham
• River Ouse at Goldbridge

The notably low monthly mean flows for the River Lymington at Brockenhurst were the fifth lowest on record for August since 1960.

5. Groundwater levels   

End of month groundwater levels for August ranged from exceptionally low to above normal across SSD.

Groundwater levels were exceptionally low at:

• Carisbrooke Castle (Isle of Wight)
• Beeding Hill (West Sussex Chalk)
• Chilgrove (West Sussex Chalk)

Groundwater levels were below normal at:

• Harting Common (Western Rother Greensand)
• Catherington (East Hampshire Chalk)

Groundwater levels were normal at:

• Clanville Gate (Test Chalk)
• Lopcombe Corner (Test Chalk)
• West Meon (East Hampshire Chalk)
• Cornish Farm (East Sussex Chalk)
• Houndean Bottom (East Sussex Chalk)

Groundwater levels were above normal at:

• Preston Candover (East Hampshire Chalk)
• Youngwoods Copse (Isle of Wight)

The groundwater level at Carisbrooke Castle (Isle of Wight) is the second lowest August level since 1977. Beeding Hill (West Sussex Chalk) is the third lowest August level in a record that dates back to 1979.

6. Reservoir stocks

End of month reservoir stocks were below average for both Ardingly and Arlington Reservoirs. Ardingly Reservoir (Ouse) was at 34.3% of total capacity (LTA 73%) and Arlington Reservoir (Cuckmere) was at 56.1% of total capacity (LTA 62.75%).

7. Environmental impact 

7.1 Abstraction licence restriction

At the start of August there were 22 licence restrictions in force, which increased to 27 licence restrictions by the middle of the month. By the end of the month 26 licence restrictions were in place. These included the following.

Cessation of abstraction for:

• 3 licences on the Arun and one licence on the Loxwood Stream (Arun)
• one licences on the Pagham Rife (Sussex Coast)
• 3 licences on the River Rother and one licence on the River Lod (Western Rother Greensand)
• one on the River Meon (East Hampshire Chalk)
• 4 on the River Medina and 3 licences on the Shepherds Chine (Isle of Wight)
• one on the Lymington River and 3 on Walkford Brook (Lymington)
• one on the River Blackwater (Hampshire Tertiaries)

Restrictions on abstraction rates for:

• one on the River Meon (East Hampshire Chalk)
• one on the Calbourne (Isle of Wight)
• one on the River Blackwater (Hampshire Tertiaries)

7.2 Flood Warnings in Force

There were 3 flood alerts issued in August 2025 associated with the rainfall at the end of the month. The first flood alert was on 28 August in the Ouse catchment. On 29 August flood alerts were issued for the Western Yar on the Isle of Wight and the Aldingbourne and Barnham Rifes in West Sussex.

Author: HydrologySSD@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.