Research and analysis

Solent and South Downs water situation report: April 2026 summary

Updated 13 May 2026

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 April, receiving 17% (9.4mm) of long term average (LTA) of 56.5mm. Monthly mean river flows for April ranged from notably low to above normal across SSD. End of month groundwater levels for April ranged from below normal to notably high. Soils across SSD ended the month drier than the LTA for April. End of month reservoir stocks were above average at Ardingly Reservoir (Ouse) and were below average at Arlington Reservoir (Cuckmere).

2. Rainfall

SSD had below average rainfall in April receiving only 17% (9.4mm) of LTA (56.5mm). Monthly total rainfall was within the notably low range for hydrological areas units in Hampshire, Isle of Wight, and West Sussex. Areal units in East Sussex received rainfall in the exceptionally low range.

The lowest monthly total rainfall was in the Pevensey Levels areal unit with 3mm, 6% of LTA (47.6mm). Exceptionally low rainfall was also received in the Cuckmere (7%, 3.5mm), Ouse (10%, 5mm) and Adur (10%, 7mm) areal units. Lymington areal unit received the highest monthly rainfall with 25% (14mm) of LTA (58.2mm). This was followed closely by the East Hampshire Chalk and Western Rother Greensand areal units which received 24% and 23% of their LTAs respectively.

Most of the month was dry except for 1 to 4 April and 11 to 17 April. Rain gauges in East Sussex, and along the southeast coast recorded more than 25 dry days. There were 22 dry days on average in April in SSD. The highest daily rainfall total, 9.0mm, was recorded on 11 April, at Cowes WTW RG (Isle of Wight).

April rainfall totals were the fourth lowest on record for the Cuckmere areal unit, and fifth lowest for the Pevensey Levels. In the East Sussex Chalk and Ouse areal units the rainfall totals were the sixth and seventh lowest on record, respectively. The March to April 2-month period has been the fourth driest on record for the Pevensey Levels areal unit and the sixth driest for the Cuckmere areal unit.

In contrast, the January to April 4-month period has been the seventh wettest on record for SSD as a whole. The 4-month totals were also the seventh highest on record for East Hampshire Chalk, Isle of Wight, Western Rother Greensand, Hampshire Tertiaries and Lymington areal units.

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

3. Soil moisture deficit and recharge

Soil moisture deficits (SMDs) are greater than LTA for April. Soils across SSD ended the month drier than average for April due to the lack of rainfall.

4. River flows

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

Flows were notably low on the:

• River Lymington at Brockenhurst
• River Arun at Alfoldean

Flows were below normal on the:

• River Adur at Sakeham
• River Ouse at Goldbridge
• River Cuckmere at Cowbeech

Flows were normal on the:

• River Test at Chilbolton
• River Test at Broadlands
• River Meon at Mislingford
• River Wallington at North Fareham
• River Rother at Iping Mill
• River Medina at Blackwater

Flows were above normal on the:

• River Itchen at Allbrook and Highbridge

The notably low monthly mean flows for the River Arun at Alfoldean ranked the third lowest for April since 1970. The monthly mean flows for April ranked the eight lowest for the River Lymington at Brockenhurst since 1960.

5. Groundwater levels 

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

Groundwater levels were below normal at Carisbrooke Castle (Isle of Wight)

Groundwater levels were normal at:

• Lopcombe Corner (Test Chalk)
• Harting Common (Western Rother Greensand)
• Beeding Hill (West Sussex Chalk)
• Houndean Bottom (East Sussex Chalk)

Groundwater levels were above normal at:

• Clanville Gate (Test Chalk)
• Preston Candover (East Hampshire Chalk)
• Youngwoods Copse (Isle of Wight)
• Catherington (East Hampshire Chalk)
• Chilgrove (West Sussex Chalk)

Groundwater levels were notably high at:

• West Meon (East Hampshire Chalk)
• Cornish Farm (East Sussex Chalk)

The notably high groundwater level at Cornish Farm was the fourth highest on record for April since 1981.

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 was at 99.5% of total capacity (LTA 98%) and Arlington Reservoir was at 91.2% of total capacity (LTA 97.2%).

7. Environmental impact 

No new license restrictions were triggered during the month. At the start of April there were two licence restrictions in force, which remained in force throughout the month:

• Cessation of abstraction for one licence on the River Ouse
• Restriction on abstraction rates for one licence on the River Meon

We issued no new flood alerts or flood warnings in April.

At the start of April there were 7 groundwater alerts in force, all issued during the previous months. However, throughout April all alerts were removed as the situation improved. At the end of April, no groundwater flood alerts remained in force.

County	No. of individual areas	Area where groundwater flood alerts were issued	Removal Date
Hampshire	2	Bishops Sutton, Deane and Ashe in North Hampshire	1 April 2026
Sussex	1	West Dean, Singleton, Charlton, East Dean and Chilgrove	2 April 2026
Hampshire	3	Twyford and Hensting, Hursley and villages surrounding Andover	7 April 2026

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.