Research and analysis

Solent and South Downs water situation report: March 2025 summary

Updated 14 April 2025

Applies to England

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

1. Summary

Solent and South Downs (SSD) had well below average rainfall in March, receiving 12% (8mm) of the long term average (LTA of 67mm). Monthly mean river flows across SSD ranged from notably low to notably high and the end of month groundwater levels ranged from below normal to notably high. Soils across SSD ended the month much drier than the average for March. End of month reservoir stocks were above average at Ardingly Reservoir (Ouse) and close to average at Arlington Reservoir (Cuckmere).

2. Rainfall

SSD had well below average rainfall in March, receiving 12% (8mm) of the LTA (67mm). The East Sussex Chalk and the Isle of Wight areal units received the highest rainfall during March both with 10mm. This represents 16% of LTA (65.1mm) for the East Sussex Chalk areal unit and 14% of LTA (67mm) for the Isle of Wight areal unit. The Arun areal unit received the lowest rainfall with only 5mm for the whole month.

Despite March being such a dry month there were very few completely dry days across the area. Most of the rainfall was recorded on 23 March with the highest daily rainfall totals at the following locations:

• 9.1mm at Cowbeech (Cuckmere)
• 8.7mm at Brockenhurst (Lymington)
• 8.6mm at Vines Cross (Cuckmere)

For SSD as a whole, the March totals were the fifth lowest on record. For SSD and the majority of the areal units the March totals were the lowest since 1990. For the Arun and Test Chalk areal units the March totals were the fourth lowest on record and the lowest since 1961.

Figures for the 18-month period (starting October) were the third highest total for SSD and the second highest for the East Hampshire Chalk, Isle of Wight and Test Chalk areal units. For the 24-month period (starting April) it was the fifth highest total for SSD and the highest for the Test Chalk areal unit.

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

3. Soil moisture deficit and recharge

Soils across SSD ended the month much drier than the LTA for March.

4. River flows

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

Flows were notably low on the:

• River Arun at Alfoldean
• River Lymington at Brockenhurst

Flows were below normal on the:

• River Wallington at North Fareham
• River Medina at Blackwater
• River Adur at Sakeham
• River Ouse at Goldbridge
• River Cuckmere at Cowbeech

Flows were normal on the:

• River Test at Chilbolton
• River Rother at Iping Mill

Flows were above normal on the:

• River Meon at Mislingford

Flows were notably high on the:

• River Test at Broadlands
• River Itchen at Allbrook and Highbridge

The monthly mean flows for March were the seventh highest on record for the River Test at Broadlands (1957) and the River Itchen at Allbrook and Highbridge (1958) and the seventh lowest on record for the River Arun at Alfoldean (1970).

5. Groundwater levels   

End of month groundwater levels for March ranged from below normal to notably high.

Groundwater levels were below normal at:

• Carisbrooke Castle (Isle of Wight)

Groundwater levels were normal at:

• Beeding Hill (West Sussex Chalk)
• Houndean Bottom (East Sussex Chalk)
• Cornish Farm (East Sussex Chalk)
• Harting Common (Western Rother Greensand)

Groundwater levels were above normal at:

• Catherington (East Hampshire Chalk)
• Chilgrove (West Sussex Chalk)
• Youngwoods Copse (Isle of Wight)

Groundwater levels were notably high at:

• Clanville Gate (Test Chalk)
• Lopcombe Corner (Test Chalk)
• Preston Candover (East Hampshire Chalk)
• West Meon (East Hampshire Chalk)

The notably high groundwater level at Preston Candover was the fifth highest for March in a record going back to 1975.

6. Reservoir stocks

End of month reservoir stocks were above average at Ardingly Reservoir (Ouse) and were around average at Arlington Reservoir (Cuckmere). Ardingly Reservoir (Ouse) was at 99.6% of total capacity (LTA 97%), and Arlington Reservoir (Cuckmere) was at 98.2% of total capacity (LTA 99%).

7. Environmental impact 

7.1 Abstraction licence restrictions:

During March there were a total of 3 licence restrictions in force, 2 cessations and one reduced abstraction rate. One cessation was in force on the River Lymington (New Forest) for all of March and the other on the River Rother was only in force during the last week. The reduced abstraction rate restriction was in force on the River Meon (East Hampshire).

7.2 Flood Alerts:

During March there were 3 groundwater flood alerts in place in Hampshire.

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.