Research and analysis

Solent and South Downs water situation report: August 2026 summary

Updated 14 September 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 August, receiving 63% (42mm) of long term average (LTA) of 66mm. Monthly mean river flows across SSD ranged from exceptionally low to normal in August. Groundwater levels ranged from notably low to above normal in July. Soils in all the hydrological areas ended the month drier than average for August. End of month reservoir stocks decreased and were below average at Ardingly Reservoir (Ouse) (38% of LTA) and at Arlington Reservoir (Cuckmere) (48% of LTA).

2. Rainfall

SSD had below average rainfall in August, receiving 63% (42mm) of the LTA (66mm). However, the overall SSD figure masks the distribution of rainfall across the hydrological areas. The Hampshire Tertiaries hydrological area in the west of the SSD received the least rainfall in August with 32mm. This represents 49% of LTA (64.7mm). The Pevensey Levels hydrological area in the east received the most rainfall with 62mm which is 96% of the LTA (64.6mm).

The first part of August had very little, if any, rainfall as the hot, dry conditions which began in the second half of June and continued throughout July predominated. The pattern finally changed on 18 August, and more typical summer weather was experienced for the remainder of the month. The 19 and 30 of August recorded the most significant rainfall across the area. The highest daily rainfall totals were as follows:

• 45.7mm was recorded at Pevensey RG in the Pevensey Levels hydrological area on 19 August, which represented 46% of the recorded monthly total (99.0mm)
• 37.6mm was recorded at Ashington in the Adur hydrological area on 30 August, which represented 43% of the recorded monthly total (88.0mm)

The April to August 5-month period was the fifth driest for the Test Chalk hydrological area. The March to August 6-month period was the fourth driest for Sussex Coast hydrological area.

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 August despite the rainfall in the second part of the month. There was no effective rainfall across SSD and so no recharge this month.

4. River flows

Monthly mean river flows at the main reporting sites across SSD ranged from exceptionally low to normal in August. Flows at many sites were boosted by rainfall in the second half of the month. However, the response was muted because of the dryness of the catchments following the extended hot and dry conditions over previous months.

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 and therefore dependant on rainfall. Flows ranged between 12% and 34% of the LTA. The monthly mean flows for August was the second lowest on record for the River Arun at Alfoldean since 1970, and third lowest for the Lymington at the Brockenhurst since 1960.

The flows at the Wallington River at North Fareham were classed as notably low with flows at 32% of the LTA. The geology and behaviour of the Wallington is complicated but during summer months its flows is dependent on rainfall hence flows being notably low. Flows were the third lowest for August for the Wallington at North Fareham in a record going back to 1976.

Monthly mean flows at four sites were classed in the below normal range. These were the River Test at Broadlands, the River Test at Chilbolton River, the Adur at Sakeham and the River Cuckmere at Cowbeech. The flows at these sites ranged between 51% and 86% of the LTA. 

Flows at the rest of the indicator sites were classed as normal and ranged between 85% and 99% of the LTA. There were the Itchen at Allbrook and Highbridge, the Meon at Mislingford, the Medina at Blackwater and the Rother at Iping Mill. These sites are in predominantly groundwater fed catchments, which means rivers are sustained by baseflow. Monthly mean flows were also classed as normal on the Ouse at Goldbridge. Flows in this river are supported by the augmentation releases from the Ardingly reservoir.

5. Groundwater levels

End of month groundwater levels for August ranged from notably 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.

However, the end of month groundwater level at Youngwoods Copse (Isle of Wight) was above normal. Youngwoods Copse monitors greensand geology which unlike the surrounding Chalk has a delayed reaction to conditions. This also sustains a baseflow to the Eastern Yar for longer than other rivers on the Island.

In addition, end of month groundwater level at Houndean Bottom (East Sussex Chalk) were below normal, while Beeding Hill (West Sussex Chalk), Carisbrooke Castle (Isle of Wight) and Chilgrove (West Sussex Chalk) were notably low despite being Chalk units. Carisbrooke Castle and Chilgrove are notably low despite being Chalk units due to the highly fractured and low storage nature of their geology. Consequently, these sites have large and rapid groundwater level rises and falls.

6. Reservoir stocks

End of month reservoir stocks have further declined this month and remain below average at Ardingly Reservoir (Ouse) and at Arlington Reservoir (Cuckmere). Ardingly Reservoir (Ouse) was at 38.4% of total capacity (LTA 73%) and Arlington Reservoir (Cuckmere) was at 48% of total capacity (LTA 62.75%) compared to both being at 61% at the end of July. 

7. Environmental impacts

7.1 Water Resources

SSD moved into drought status at the start of August due to the lack of rainfall and declining water resources conditions. There are active Temporary Use Bans (TUBs) in SSD covering Southern Water – Hampshire and the Isle of Wight and South East Water – Sussex.

There were 25 licence restrictions in place during August; 21 non-public water supply (PWS) and 4 PWS. In addition, PWS transfer and augmentation schemes are in place on the Isle of Wight and River Ems. Table 10.5 in the appendix provides more information.

Arun & Western Streams

There were 9 restrictions or cessations in place throughout August: one on the River Lod, 3 on the Western Rother, four on the River Arun and one on the Pagham Rife.

Cuckmere & Pevensey Levels

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

East Hampshire

There was one cessation in place throughout the month for a licence on the River Meon.

Isle of Wight

Five restrictions on the River Medina were in place at throughout August. Additionally, the transfer scheme was in operation.

New Forest

There were 4 cessations in place throughout the month, 3 on the Walkford Brook and one on the River Lymington.

Test and Itchen

There were four restrictions or cessations in place during August. Two on the River Ower and one on the River Test. The abstraction restriction for the PWS licence at Gaters Mill on the River Itchen also came into force.

7.2 Flood Warning and Alerts

Flooding can happen during a drought and will often be localised, and of a short duration. There were 5 flood alerts issued in August all on the 26 of the month – 4 in East Sussex and one in West Sussex.

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

Contact Details: 03708 506 506, HydrologySSD@environment-agency.gov.uk

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.