Research and analysis

Devon and Cornwall water situation: August 2025 summary

Updated 12 September 2025

Applies to England

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

1. Summary

Devon and Cornwall received 68% of the August long term average (LTA) rainfall, which was normal for the time of year. Soil moisture deficit (SMD) increased through most of August before decreasing significantly in response to the rainfall towards the end of the month. Monthly mean river flows were notably low to normal for the time of year across the area. Groundwater levels ended the month between below normal and exceptionally high for the time of year. Total reservoir storage across Devon and Cornwall ended the month at 53%, with Wimbleball, Colliford and Roadford at 39%, 48% and 65% respectively at the end of August.

2. Rainfall

Devon and Cornwall received 65mm of rain during August (68% of the August LTA), which is normal for the time of year. The most significant periods of rain occurred on 4, 28 and 30 to 31 August, with the most intense rainfall falling on 28 August.

In August, rainfall was normal in Cornwall and in most of Devon, except for the Torridge and Hartland Streams, the Taw and North Devon Streams, and the Exe hydrological areas where cumulative rainfall was below normal for the time of year. Cumulative rainfall was normal in the last 3 months, across much of Devon and Cornwall, except the Exe and the Otter Sid Axe and Lim, where rainfall was below normal for the time of year. In the last 6 months, cumulative rainfall was normal for most of Cornwall (apart from Seaton Looe and Fowey), below normal for the western Devon hydrological areas, and notably low for the eastern Devon hydrological areas, for the time of year. In the last 12 months, cumulative rainfall across Devon and Cornwall was normal for the time of year.

3. Soil moisture deficit

SMD increased through much of August, exceeding the SMD seen in August 2022, and nearing the historic maximum before decreasing significantly in response to the rainfall towards the end of the month. Soils ended the month drier than the LTA for the time of year and slightly higher than the SMD at the same time in 2024.

The average deficit at the end of August was between 71 and 100mm in most of Devon and Cornwall except for the Seaton, Looe and Fowey, Tamar, and Teign and Torbay hydrological areas where the average deficit was between 41 and 70mm. The average deficit was lowest in the Avon, Dart and Erme hydrological area, where the average deficit was between 11 and 40mm and highest in the Otter, Sid, Axe and Lim hydrological area, where the average deficit was between 101 and 130mm.

SMD was 26 to 50mm drier (higher) than the long term average deficit for August in North Devon, the Exe and North Cornwall. All other hydrological areas ranged from 25mm drier (higher) than the LTA to 25mm wetter (lower) than the LTA for August.

4. River flows

August monthly mean river flows were below normal at most sites across Devon and Cornwall, except for some sites in mid and north Devon where monthly mean levels were notably low for the time of year. Two sites, Truro on the River Kenwyn and Whitford on the River Axe recorded normal monthly mean river flows for the time of year.

All sites experienced a drop in daily mean river flows through most of August, with all sites reaching below normal to exceptionally low flows, before experiencing a spike in river levels after the heavy rain towards the end of the month. The most prominent peaks were recorded at the River Kenwyn (Truro), the River Gannel (Gwills) and the River Otter (Dotton); a much less significant response was recorded at the River Torridge (Torrington), the River Taw (Umberleigh), the River Teign (Chudleigh), and the River Exe (Thorverton). On 31 August, reporting sites recorded notably low to notably high daily mean flows for the time of year.

Due to data accuracy concerns, St Erth on the River Hayle has been excluded from the August report.

5. Groundwater levels   

On 31 August, groundwater levels were classed as follows:

• below normal at Winnards Perch (monitoring the Staddon Formation)
• normal at Bussells No7A (monitoring the Dawlish sandstone), Coleford Production (monitoring the Permian Breccias and Sandstones), Woodbury Common No2 (monitoring the Budleigh Salterton Pebble Beds), and Woodleys No1 (monitoring the Otterton Sandstone Formation)
• above normal at Branscombe Lane (monitoring the Dawlish Sandstone)
• exceptionally high at Whitlands (monitoring the Upper Greensand)

Groundwater levels at all sites continue to be in recession, which is normal for the time of year.

6. Reservoir stocks

Total reservoir storage was 53% at the end of August, which is an overall decrease of 12% since the end of July. This is higher than storage at the same time in 2022 (the most recent drought year), which was 39%. At the end of August, storage at Wimbleball, Colliford and Roadford was 39%, 48% and 65% respectively, compared to 35%, 30% and 46% at the same time in 2022.