Research and analysis

Solent and South Downs water situation report: July 2024 summary

Updated 14 August 2024

Applies to England

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

1. Summary

Solent and South Downs (SSD) had above average rainfall in July, receiving 165% (78mm) of the long term average (LTA) rainfall (47.2mm). Monthly mean river flows across SSD ranged from normal to exceptionally high. End of month groundwater levels ranged from normal to exceptionally high. Soils across SSD ended the month slightly drier than the average for July. End of month reservoir stocks were above average at Ardingly Reservoir (Ouse) and were just below average at Arlington Reservoir (Cuckmere).

2. Rainfall

SSD had above average rainfall in July, receiving 165% (78mm) of the LTA (47.2mm). The West Sussex Chalk areal unit in central SSD received the highest rainfall with 187% of LTA (50.7mm). The Pevensey Levels unit received the lowest rainfall with 122% of LTA (47.3mm).

July was a month of dry hot periods interspersed with heavy downpours from numerous thunderstorms. The highest daily rainfall totals for the month were all recorded on 15 July:

• 31mm was recorded at Ferry PS RG (Sussex Coast)
• 30mm at Broadwater RG (West Sussex Chalk)
• 27mm at Worlds End RG (Hampshire Tertiaries)
• 26mm at Ardingly RG (Ouse) and at Westergate RG (Sussex Coast)

These highest daily rainfall totals represent, on average, a third of the month’s total rainfall in only one day. Heavy rainfall of up to 24mm was also experienced on 5 July and 13 July but the rainfall on these days was much more localised. 

July rainfall, while above average, it is not notable. However, the water year from October to July is second wettest on record for SSD area, since 1871. All the SSD rainfall units ranked in the top 3 wettest October to July period on record. The Hampshire Tertiaries, Lymington, Isle of Wight, West Sussex Chalk, Sussex Coast, and Western Rother Greensand units all ranked as wettest for October to July.

3. Soil moisture deficit and recharge

Soils across SSD ended the month slightly drier (84mm) than the average for July (81mm).

4. River flows

Monthly mean river flows across SSD ranged from normal to exceptionally high.

Flows were normal at:

• River Cuckmere at Cowbeech

Flows were above normal at:

• River Arun at Alfoldean
• River Test at Broadlands
• River Lymington at Brockenhurst
• River Test at Chilbolton
• River Meon at Mislingford
• River Wallington at North Fareham
• River Adur at Sakeham

Flows were notably high at:

• River Ouse at Goldbridge
• River Rother at Iping Mill

Flows were exceptionally high at:

• River Itchen at Allbrook and Highbridge

The recorded flow data for River Medina at Blackwater are correct but are not reflective of the current total flow of the river. Works upstream of the weir may have altered the flow split between the river and a flood relief channel. This may have resulted in flow bypassing the weir and therefore not recorded. Investigation is ongoing.

The monthly mean flows for July were the second highest on record at Allbrook and Highbridge (Itchen), in a record starting in 1959. Flows for Iping Mill (Western Rother) were the sixth highest on record for July since 1966.

5. Groundwater levels        

End of month groundwater levels for July ranged from normal to exceptionally high.

Groundwater levels were normal at:

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

Groundwater levels were above normal at:

• Catherington (East Hampshire Chalk)
• Harting Common (Western Rother Greensand)
• Houndean Bottom (East Sussex Chalk)
• Chilgrove (West Sussex Chalk)

Groundwater levels were notably high at:

• Cornish Farm (East Sussex Chalk)
• Lopcombe Corner (Test Chalk)

Groundwater levels were exceptionally high at:

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

Groundwater levels for July were the second highest on record at West Meon (since 1986), Youngwoods Copse (since 1978), and Preston Candover (since 1975). Groundwater levels were the third highest on record at Clanville Gate and fourth highest at Cornish Farm since 1966 and 1981 respectively.

6. Reservoir stocks

End of month reservoir stocks were:

• above average at Ardingly Reservoir (Ouse) with 90.8% of total capacity (LTA 82%)
• below average at Arlington Reservoir (Cuckmere) with 70.4% of total capacity (LTA 73.4%).

7. Environmental impact 

During July there was a reduced abstraction rates restriction on the river Meon in force and the Cuckmere and one cessation on the Loxwood Stream (Arun).

There were no fluvial Flood Alerts or Flood Warnings issued in SSD during July.

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.