Research and analysis

Devon and Cornwall water situation: September 2025 summary

Updated 14 October 2025

Applies to England

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

1. Summary

Devon and Cornwall received 166% of the September long term average (LTA) rainfall, which was above normal for the time of year. Soil moisture deficit (SMD) decreased significantly during the first half of September, before increasing slightly towards the end of the month. Monthly mean river flows were normal to above normal for the time of year across the area. Groundwater levels ended the month between normal and exceptionally high for the time of year. Total reservoir storage across Devon and Cornwall ended September at 51%, with:

• Wimbleball at 32%
• Colliford at 44%
• Roadford at 59%

2. Rainfall

Devon and Cornwall received 146mm of rain during September (166% of the September LTA), which is above normal for the time of year. Between 1 and 20 September, 95% of the month’s rain was recorded, with the remainder of the month mostly dry.

In September, rainfall was mostly above normal for the time of year in Devon, except for the Torridge and Hartland Streams which was notably high. In Cornwall, rainfall was notably high, except for the Fal and St Austell and Seaton, Looe and Fowey hydrological areas where cumulative rainfall was above normal for the time of year. Cumulative rainfall was normal in the last 3 months across the area. Over the last 6 months, cumulative rainfall was normal in the east and mostly above normal in the west, except the Fal and St Austell hydrological area which was normal. Cumulative rainfall over the last 12 months has been normal across Devon and Cornwall

3. Soil moisture deficit

SMD decreased significantly through the first half of September, in response to the rainfall during this period, before increasing again towards the end of the month. Soils ended the month almost level with the LTA for the time of year and higher (drier) than the SMD at the same time in 2024.

The average deficit at the end of September was between 11mm and 40mm in most of Devon and Cornwall. Eastern and western areas were drier, with the Exe, North Cornwall, Fal and St Austell and West Cornwall hydrological areas recording a deficit of between 41 and 70mm. The highest average deficit was in the Otter, Sid, Axe and Lim hydrological area, which was between 71mm and 100mm.

SMD was 6mm to 25mm drier (higher) than the LTA deficit for September in the Otter, Sid, Axe and Lim hydrological area. In the Exe, North Cornwall, Fal and St Austell and West Cornwall hydrological areas, the SMD was between 5mm wetter (lower) and 5mm drier (higher) than the LTA for September. All other hydrological areas ranged from a 25mm wetter (lower) to 6mm wetter (lower) difference from the LTA for September.

4. River flows

September monthly mean river flows were normal at most sites across Devon and Cornwall. The rivers Torridge (Torrington), Dart (Bellever and Austins Bridge), Camel (Bodmin Dunmere) and Kenwyn (Truro) all recorded above normal river flows for the month.

All sites experienced an increase in daily mean river flows during the first two-thirds of September in response to the rainfall, with all sites reaching notably high or exceptionally high flows for the time of year between 3 September and 20 September, except the River Fowey (Restormel) which peaked at above normal flows for the time of year. On 30 September, all reporting sites recorded normal daily mean flows for the time of year.

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

5. Groundwater levels   

On 30 September, groundwater levels were classed as:

• 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) and Winnards Perch (monitoring the Staddon Formation)
• exceptionally high at Whitlands (monitoring the Upper Greensand)

Groundwater levels at most sites continue to be in recession, except for Winnards Perch, which has increased from below normal to above normal since the previous report. Levels at this site respond quickly to rainfall due to the low storage of the secondary aquifer which it monitors. Its hydrograph may now have started its rising limb.

6. Reservoir stocks

Total reservoir storage was 51% at the end of September, which is an overall decrease of 2% since the end of August. This is higher than storage at the same time in 2022 (the most recent drought year), which was 33%. At the end of September, storage at Wimbleball, Colliford and Roadford was 32%, 44% and 59% respectively, compared to 24%, 21% and 39% at the same time in 2022.

Author: Devon and Cornwall Hydrology, hydrology.dandc@environment-agency.gov.uk

All data are provisional and maybe subject to revision. The views expressed in this document are not necessarily the views of the Environment Agency. Its officers, servants, or agents accept no liability for loss or damage arising from the interpretation or use of the information, or reliance upon views contained in this report.