Research and analysis

Solent and South Downs water situation report: September 2026 summary

Updated 14 October 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 September, receiving 64% (42.3mm) of long term average (LTA) of 66.2mm. Monthly mean river flows ranged from exceptionally low to normal in September across SSD. End of month groundwater levels ranged from exceptionally low to above normal in September. Soils in all the hydrological areas ended the month drier than average for September. End of month reservoir stocks decreased and were below average at both Ardingly Reservoir (Ouse) with 22.8% of LTA, and at Arlington Reservoir (Cuckmere) with 35.5% of LTA.

2. Rainfall

SSD had below average rainfall in September, receiving 64% (42.3mm) of the LTA (66.2mm). However, the aggregated values for SSD ​​do not represent the full picture of rainfall distribution across the hydrological areas. The coastal hydrological areas received more rainfall, between 61% and 79% of LTA, with Isle of Wight receiving the most rainfall, 52mm (LTA is 66mm). While, the non-coastal areas received less rainfall, between 54% and 68% of LTA, with Arun areal unit receiving the least rainfall in September with 35mm (LTA is 66mm).

In September the weather was changeable with a drier spell between 20 and 27 September. The 5 wettest days were the 7, 8, 10, 17 and 30 September. About half of the monthly rainfall in this month fell on 7 to 8 September.

The highest daily totals were all recorded on 7 September:

• 22.9mm was recorded at Wroxall RG on the Isle of Wight
• 22.2mm was recorded at Peel Common (Gosport), in the Hampshire Tertiaries
• 20.4mm was recorded at Efford (in the New Forest), in the Lymington hydrological area

Although September rainfall totals were below average in the SSD area, it was in the normal range for the majority of the hydrological areas. Only the rainfall totals for the Test Chalk and for the Arun hydrological areas were in the below normal range.

The July to September 3-month period has been the driest for the Arun and for the Western Rother Greensand areal units. It was the second driest for the East Hampshire Chalk, and the third driest for the Hampshire Tertiaries and for the Lymington areal units. For the SSD area, the last 3 months’ rainfall totals were the fourth lowest on record.

The April to September 6-month period has been the third driest for the SSD and for the Arun and the Ouse areal units. It was also the second driest for the Test Chalk areal unit, only in 1921 was there less rainfall during the same period.

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

3. Soil moisture deficit and recharge

Soils in all the hydrological areas ended the month drier than average for September due to the accumulated rainfall deficit throughout the last 6 to 7 months. Soil moisture deficits (SMDs) continue to rise. On 30 September SMD ranged between 174mm and 209mm in the hydrological areas which is well above the LTA of 79mm to 109mm. There was little or no effective rainfall across SSD in the hydrological areas consequently, there was no recharge this month.

4. River flows

Monthly mean river flows ranged from exceptionally low to normal in September.

Flows at most sites had a peak after the rainfall on the 7 and 8 of September but flows afterwards were either declining or at best stabilising across the SSD catchments.

The monthly mean flows at the River Lymington at the Brockenhurst, and the River Arun at Alfoldean were classed as exceptionally low. These rivers are in clay catchments with low baseflows making them more dependent on rainfall. The monthly mean flows at the Brockenhurst and at Alfoldean were both the third lowest on record since 1960 and 1970, respectively. Monthly mean flows were 17% of the LTA for the River Lymington at the Brockenhurst and 32% of the LTA for the River Arun at Alfoldean.

The monthly mean flow at the Wallington River at North Fareham was classed as below normal with flow at 38% of the LTA. The geology and behaviour of the Wallington is complex but during summer months its flows is dependent on rainfall. The monthly mean flow was the eighth lowest for September for the Wallington at North Fareham in a record going back to 1976.

The monthly mean flow at the River Test at Broadlands was also classed as below normal with flow with 81% of the LTA, which was the 10th lowest for September on record since 1958.

Monthly mean flows at the rest of the indicator sites were classed as normal and ranged between 46% and 94% of the LTA.

5. Groundwater levels    

End of month groundwater levels for September ranged from exceptionally low to above normal.

Groundwater levels at all sites continued to recede in line with the expected trend for this time of the year. Despite the hot and dry weather over the recent month’s groundwater levels remain at normal levels at the majority of reported sites.

End of month groundwater levels were normal at Clanville Gate and at Lopcombe Corner, both sites are in the Test Chalk. End of month groundwater levels were also normal at Preston Candover, at West Meon and at Catherington; all three sites are in the East Hampshire Chalk. End of month groundwater level at Cornish Farm located in the East Sussex Chalk also was in the normal range.

End of month groundwater levels at Harting Common (Western Rother Greensand) and at Houndean Bottom (East Sussex Chalk) were below normal. While notably low levels were recorded at Chilgrove (West Sussex Chalk) and Beeding Hill (West Sussex Chalk).

On the Isle of Wight, at Carisbrooke Castle, the end of month groundwater level was in the exceptionally low range, which is the second lowest on record since 1977. However, at the neighbouring greensand aquifer on the island, at Youngwoods Copse, the end of month groundwater level was in the above normal range.

6. Reservoir stocks

End of month reservoir stocks have declined further this month and remain below average at Ardingly Reservoir (Ouse) and at Arlington Reservoir (Cuckmere). Ardingly Reservoir was at 22.8% of total capacity (LTA 68%) and Arlington Reservoir was at 38.5% of total capacity (LTA 57.5%).

7. Environmental impact 

SSD moved into drought status at the start of August due to the lack of rainfall and declining water resources conditions. There are temporary use bans (TUBs) in effect in the SSD area, impacting supply areas of Southern Water (Hampshire and the Isle of Wight) and South East Water (Sussex).

There were 26 licence restrictions in place during September, 5 public water supply and 21 non-public water supply.

7.1 Arun and Western Streams:

At the beginning of the month there were 3 restrictions in place, one on each of the:

• River Arun
• River Lod in the Western Rother catchment
• Pagham Rife.

From the second week 9 restrictions in were in effect. An additional 6 hands off flow (HoF) were triggered 3 on the River Arun and 3 on the River Rother. On the third week, 5 licences could restart abstraction and 4 stayed in cessation:

• 2 on the River Arun
• one on the River Lod
• one on the Pagham Rife

From 21 September, the 5 licenses that had been restarted on the previous week, went back to cessation once again and there were 9 restrictions in place:

• 4 on the River Arun
• one on the River Lod
• one on the Pagham Rife
• 3 on the River Rother

All these remained in place until the end of the month.

The Ems augmentation scheme is in operation since 18 August.

7.2 Cuckmere and Pevensey Levels:

The restriction on the abstraction rate for the PWS licence on the Wallers Haven was in place throughout the month.

7.3 East Hampshire

There were 2 restrictions in place throughout the month, both on the River Meon, one cessation and one abstraction rate condition (PWS).

7.4 Isle of Wight

Six restrictions were in place throughout September on the Isle of Wight. Four on the River Medina, one abstraction aggregate volume condition for the PWS licence on the Caul Bourne and the Medina-Yar transfer scheme was in operation.

7.5 New Forest

At the beginning of the month 3 restrictions were in place, all on the Walkford Brook. From the second week 2 licences could restart abstraction and only one stayed in cessation on the Walkford Brook.

On the third week there were 3 restrictions in place again, all on the Walkford Brook. From 21 September, another HoF was triggered, so from that day on there were 4 restrictions in effect until the end of the month: three on the Walkford Brook and one on the River Lymington.

7.6 Test and Itchen

At the beginning of the month there were 3 restrictions in place: 2 on the River Ower and one on the River Test. From the second week one licence could restart abstraction and 2 stayed in cessation both on the River Test.

On the third week there was no restriction in place. From 21 September, there were 3 restrictions in place again, 2 on the River Ower and one on the River Test and these were in effect until the end of the month.

The abstraction restriction for the PWS licence at Gaters Mill on the River Itchen was also in effect throughout the month.

Author: Groundwater, Hydrology and Contaminated Land Team, Solent and South Downs Area, 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.