Research and analysis

Solent and South Downs water situation report: June 2026 summary

Updated 14 July 2026

Applies to England

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

Solent and South Downs (SSD) had below average rainfall in June, receiving 136% (75mm) of long term average (LTA) of 56mm. Monthly mean river flows for June ranged from below normal to above normal across SSD. End of month groundwater levels for June ranged from below normal to notably high. Soils across SSD ended the month drier than the LTA for June. End of month reservoir stocks were below average at Ardingly Reservoir (Ouse) and at Arlington Reservoir (Cuckmere).

1. Rainfall

SSD had above average rainfall in June receiving 136% (75mm) of LTA (56mm). The lowest monthly total rainfall was in the Test Chalk areal unit with 66mm, 114% of LTA (58mm). The Sussex Coast followed close behind with 118% (60mm) of LTA (51mm). The highest monthly total rainfall was received by the Arun areal unit with 158% (84mm) of LTA (53mm). The second highest was received by the adjacent Western Rother Greensand unit with 155% (93mm) of LTA (60mm).

June was a month of 2 halves. Rainfall was concentrated into the first half while the second half had dry and hot conditions which built to a sweeping heatwave across the UK. On average 93% of the total June rainfall was recorded between 1 and 11 June. All top 5 highest daily totals were recorded on 1 June. The highest daily total of 54 mm was recorded at World End (Hampshire Tertiaries). This represented 45% of the total June rainfall for the gauge. The second and third highest totals, 40mm and 38mm respectively, were recorded at Petersfield RG and Princes Marsh RG both in the Western Rother Greensand unit.

By exception on 26 June while the rest of SSD had no rain the raingauges on the eastern side of SSD (Ouse, Cuckmere, and Pevensey Levels units) recorded about 20% of their total monthly rainfall. These units had only recorded around 60% of their total rainfall during the 1 to 11 June period.

Based on long-term records, June rainfall was not noteworthy.

2. Soil moisture deficit and recharge

Soil moisture deficits (SMDs) are greater than LTA for June. Soils across SSD ended the month drier than average for June.

3. River flows

Monthly mean river flows for June ranged from below normal to above normal across SSD.

Flows were below normal on the River Test at Broadlands.

Flows were normal on the:

• River Lymington at Brockenhurst
• River Test at Chilbolton
• River Itchen at Allbrook and Highbridge
• River Meon at Mislingford
• River Arun at Alfoldean
• River Ouse at Goldbridge
• River Cuckmere at Cowbeech 
• River Medina at Blackwater

Flows were above normal on the:

• River Wallington at North Fareham
• River Rother at Iping Mill
• River Adur at Sakeham

The monthly mean flows for June ranked the seventh highest for the River Wallington at North Fareham since 1976.

4. Groundwater levels

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

Groundwater levels were below normal at:

• Carisbrooke Castle (Isle of Wight)
• Beeding Hill (West Sussex Chalk)
• Houndean Bottom (East Sussex Chalk)

Groundwater levels were normal at:

• Lopcombe Corner (Test Chalk)
• Clanville Gate (Test Chalk)
• Harting Common (Western Rother Greensand)
• Catherington (East Hampshire Chalk)
• Chilgrove (West Sussex Chalk)
• West Meon (East Hampshire Chalk)
• Cornish Farm (East Sussex Chalk)

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

Groundwater levels were notably high at Youngwoods Copse (Isle of Wight).

The groundwater level at Carisbrooke Castle was the seventh lowest on record for June since 1977. At Houndean Bottom (East Sussex Chalk) the recorded level was the eighth lowest on record for June since 1977. And at Harting Common (Western Rother Greensand) end of month levels were the ninth lowest on record for June since 1984.

In contrast the notably high groundwater level at Youngwoods Copse on the Isle of Wight was the ninth highest on record (1978). The groundwater levels at Youngwoods Copse reflect those of the Lower Greensand and this geology on the IOW has a delayed response to recharge.

5. Reservoir stocks

End of month reservoir stocks were below average at both Ardingly Reservoir (Ouse) and Arlington Reservoir (Cuckmere). Ardingly Reservoir was at 86% of total capacity (LTA 91.0%) and Arlington Reservoir (Cuckmere) was at 78.9% of total capacity (LTA 83.4%).

6. Environmental impact 

In June there were 2 licence restrictions on abstraction rates for:

• one public water supply (PWS) licence on the Cuckmere (Cuckmere & Pevensey Levels)
• one licence on the River Meon (East Hampshire) which reduced to cessation later in the month

In the third week of the month 2 new restrictions were in place:

• one on the Walkford Brook (New Forest)
• one on the Western Rother (Arun & Western Streams)

Five further restrictions came into force on the fourth week;

• one on the River Lod (Arun & Western Streams)
• 2 on the River Medina (Isle of Wight)
• 2 more on the Walkford Brook (New Forest)

PWS Media-Yar transfer scheme also came into operation on 23 June.

By then end of the month restrictions were also in place for:

• one licence on the River Arun (Arun & Western Stream)
• one on the River Lymington (New Forest).

Therefore, at the end of the month there were 2 PWS restriction or low flow alleviation schemes in place and 10 non-PWS licences with restrictions in force.

No flood alerts or flood warnings were issued in June.

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.