Research and analysis

Solent and South Downs water situation report: September 2024 summary

Updated 11 October 2024

Applies to England

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

1. Summary

Solent and South Downs (SSD) had well above average rainfall in September, receiving 239% (171mm) of the long term average (LTA) rainfall (72mm). Monthly mean river flows across SSD ranged from above normal to exceptionally high. End of month groundwater levels ranged from normal to exceptionally high. Soils across SSD ended the month wetter than the average for September. End of month reservoir stocks at Ardingly Reservoir (Ouse) and at Arlington Reservoir (Cuckmere) were both below average.

2. Rainfall

SSD had well above average rainfall in September, receiving 239% (171mm) of the LTA (72mm).

During September the highest rainfall totals were recorded in the Test Chalk and East Sussex Chalk areal units with 205mm. For the Test Chalk this represented 302% of the LTA) and for East Sussex Chalk 282% of the LTA. The lowest total was 129mm in Sussex Coast (203% of the LTA) areal unit. There were no completely dry days during September. There was some significant rainfall between the 5 and 8 September with 40.7mm being recorded at Overton (Test Chalk) on the 5 September. The 13 through to the 19 of the month was largely dry and then there was a very wet end to the month. The highest daily total during September was recorded at Ardingly (Ouse) on 22 September with 63.5mm. On 26 September 48.2mm was recorded at Plumpton (East Sussex Chalk).

This September was the third wettest September on record for SSD as a whole. It was the wettest on record for the East Sussex Chalk, Ouse and Test Chalk areal units. For 18months (starting April) it was the second wettest on record for SSD as a whole. It was the wettest on record for the East Hampshire Chalk, Hampshire Tertiaries, Isle of Wight, Lymington and Test Chalk areal units. For 24months (starting October) it was the wettest on record for SSD area and all areal units (with the exception of the Pevensey Levels). All these statistics are based on records going back to 1871.

3. Soil moisture deficit and recharge

Soils across SSD ended the month much wetter than the average for September.

4. River flows

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

Flows were above normal:

• River Meon at Mislingford
• River Wallington at North Fareham

Flows were notably high:

• River Test at Chilbolton
• River Ouse at Goldbridge
• River Rother at Iping Mill

Flows were exceptionally high:

• River Arun at Alfoldean
• River Adur at Sakeham
• River Cuckmere at Cowbeech
• River Itchen at Allbrook and Highbridge
• River Lymington at Brockenhurst
• River Medina at Blackwater
• River Test at Broadlands

The monthly mean flows for September were the highest on record at Allbrook and Highbridge (Itchen), since 1959 and Sakeham (Adur) since 1967.

5. Groundwater levels   

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

Groundwater levels were normal at:

• Beeding Hill (West Sussex Chalk)
• Chilgrove (West Sussex Chalk)

Groundwater levels were above normal at:

• Carisbrooke Castle (Isle of Wight)
• Catherington (East Hampshire Chalk)
• Harting Common (Western Rother Greensand
• Houndean Bottom (East Sussex Chalk)

Groundwater levels were notably high at:

• Cornish Farm (East Sussex Chalk)
• Lopcombe Corner (Test Chalk)
• West Meon (East Hampshire Chalk)

Groundwater levels were exceptionally high at:

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

Groundwater levels for September were the highest on record at Youngwoods Copse since 1978 and second highest at Preston Candover since 1975, respectively.

6. Reservoir stocks

End of month reservoir stock was below average at Ardingly Reservoir (Ouse) with 63.5% of total capacity (LTA 68%) and at Arlington Reservoir (Cuckmere) with 45.9% of total capacity (LTA 57.7%).

7. Environmental impact 

During September there were a total of 4 licence restrictions in force, 2 cessations and 2 reduced abstraction rates.

There were cessations in force on the River Meon (East Hampshire) and on the Walkford Brook (New Forest).

There were reduced abstraction rate restrictions in force on Pagham Rife (Sussex Coast) and at Wallers Haven at Hazard’s Green (Pevensey catchment).

During September there was one Flood Warning in Sussex on 30 September. There were also 11 Flood Alerts issued with eight in Sussex and three in Hampshire and the Isle of Wight.

Author: HydrologySSD@environment-agency.gov.uk

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.