Devon and Cornwall water situation: May 2025 summary
Updated 12 June 2025
Applies to England
漏 Crown copyright 2025
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1. Summary
Devon and Cornwall received 56% of the May long term average (LTA) rainfall, which was below normal for the time of year. Soil moisture deficit (SMD) increased overall during May, ending the month higher (drier) than the LTA for the time of year. Monthly mean river flows were below normal to 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 the month at 86%, with Wimbleball, Colliford and Roadford reservoirs at 85%, 81% and 91% respectively at the end of May.
2. Rainfall
Devon and Cornwall received 40mm of rain during May (56% of the May LTA), which is below normal for the time of year. The first third of May was mostly dry, with the most significant periods of rain taking place on 10 to 11 May and 24 to 29 May. May was the second month out of the last 3 to have experienced below average rainfall.
In May, rainfall was notably low to normal across Devon and Cornwall, with most regions receiving below normal rainfall. Seaton Looe and Fowey and Avon Dart and Erme hydrological areas received normal rainfall for the time of year, and the Otter Sid Axe and Lim hydrological area received notably low rainfall for the time of year. Cumulative rainfall was notably low to normal in the last 3 months, with the hydrological areas becoming relatively drier towards the east and was below normal to normal in the last 6 months. In the last 12 months cumulative rainfall was normal for the time of year across all hydrological areas.
3. Soil moisture deficit
SMD increased at a steady rate for most of May, with a slight decrease recorded between 20 May and 27 May in response to the rainfall from 24 May onwards. The average deficit for most of Devon and Cornwall was between 41mm to 70mm, apart from west Cornwall, east Devon and parts of north Devon recording a deficit of 71mm to 100mm.
The SMD at the end of May was 26mm to 50mm above (drier than) the LTA across Devon and Cornwall for the time of year, except for the Otter, Sid, Axe and Lim catchment, where SMD was 51mm to 75mm above the LTA for the time of year.
The SMD at the end of May was higher (drier) than the LTA for the time of year and higher (drier) than the SMD at the end of May 2024.
4. River flows
May monthly mean river flows were below normal to normal for the time of year at all sites across the area.
Daily mean flows showed minimal response to the sporadic periods of rainfall throughout May and ended the month lower than they were at the beginning. On 31 May, all reporting sites recorded notably low to normal daily mean river flows for the time of year.
Due to data accuracy concerns, Chudleigh Bridge on the River Teign, Gunnislake on the River Tamar and St Erth on the River Hayle have been excluded from the May report.
5. Groundwater levels聽 聽
On 31 May, groundwater levels were classed as follows:
- normal at Bussels No7A (monitoring the Dawlish Sandstone), Coleford Production (monitoring the Permian Breccias and Sandstones), Winnards Perch (monitoring the Staddon Formation), 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 86% at the end of May, which is an overall decrease in storage by 6% since the end of April. This is less than the storage at the same time last year (98%). At the end of May, storage at Wimbleball (85%) was higher than it was at the same time in 2022 (82%) (the most recent drought year) and Roadford storage (91%) was similar to the same time in 2022 (89%). Total storage at Colliford at the end of May (81%) was higher than it was at the same time in 2022 (69%).
Author: Environment Agency, [email protected]
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.