Devon and Cornwall water situation: May 2026 summary
Updated 11 June 2026
Applies to England
© Crown copyright 2026
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Devon and Cornwall received 56mm of rain during May (79% of the May long term average – LTA), which is normal for the time of year. Soil moisture deficit (SMD) was higher (drier) than the LTA for May. May monthly mean flows ranged from notably low to normal 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 on 31 May was 84%, with Wimbleball, Colliford and Roadford at 78%, 81% and 89% respectively.
1. Rainfall
Devon and Cornwall received 56mm of rain during May (79% of the May LTA), which is normal for the time of year. Rain fell on most days during the first two-thirds of the month, particularly on and around 2 May and 18 May. From 20 May until the end of the month it was very dry throughout Devon & Cornwall.
All hydrological areas reported normal rainfall for the time of year.
Cumulative rainfall for the last 3 months was notably low across most of south and east Devon and south Cornwall hydrological areas, and below normal across the rest of the area. Over the last 6 months, rainfall was exceptionally high across the area except for the Exe and the Torridge and Hartland Streams where rainfall was notably high, and the Taw and North Devon Streams, which recorded above normal rainfall. Over the last 12 months, rainfall was notably high to exceptionally high across Cornwall, and above normal to notably high across Devon.
2. Soil moisture deficit
SMD in Devon and Cornwall increased (soils became drier) during May, due to dry weather, though there was a notable decrease mid-month in response to rainfall, and a second decrease in response to rain on 1 and 2 June. On 2 June, SMD was between 41mm and 70mm across the area, except for the West Cornwall, Exe, and Otter, Sid, Axe and Lim hydrological areas where it was between 71mm and 100mm. East Cornwall and western parts of Devon were between 6mm and 25mm higher (drier) than the LTA. The rest of the area was 26mm to 50mm higher (drier) than the LTA for May.
3. River flows
May monthly mean flows ranged from notably low to normal across the area.
Daily mean flow decreased through the month at all sites, with all sites showing a peak in the middle of the month in response to rainfall. Daily mean flows on 31 May were between exceptionally low and below normal across most sites except Restormel on the River Fowey which recorded normal flows.
4. Groundwater levels
On 31 May, groundwater levels were classed as:
- below normal at Winnards Perch (monitoring the Staddon Formation)
- normal at Coleford Production (monitoring the Permian Breccias and Sandstones)
- above normal at Bussels No7A (monitoring the Dawlish sandstone) and Woodleys No1 (monitoring the Otterton Sandstone Formation)
- notably high at Woodbury Common No2 (monitoring the Budleigh Salterton Pebble Beds), and Branscombe Lane (monitoring the Dawlish Sandstone)
- exceptionally high at Whitlands (monitoring the Upper Greensand)
Groundwater levels at all sites are in their seasonal recession. The faster-responding, lower aquifer storage sites such as Winnards Perch have responded rapidly to the recent low rainfall, in the same way as the surface water flow sites have. In contrast, groundwater levels at the sites whose aquifers have higher storage, such as Whitlands, are receding only slowly.
5. Reservoir stocks
Total reservoir storage was 84% on 31 May, which is an overall decrease of 10% since the end of April. This is higher than storage at the end of May 2022 (the most recent drought year), which was 79%. On 31 May, storage at Wimbleball, Colliford and Roadford was 78%, 81% and 89% respectively, compared to 79%, 67% and 86% 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.