Research and analysis

Devon and Cornwall water situation: April 2024 summary

Updated 15 May 2024

Applies to England

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

1. Summary

Devon and Cornwall received 167% of the April long term average (LTA) rainfall, which was notably high for the time of year. Soil moisture deficit (SMD) was 4mm in April and ended the month lower (wetter) than the LTA for the time of year. Monthly mean river flows ranged from above normal to exceptionally high for the time of year across all reporting stations. Levels at all reporting groundwater sites ranged from above normal to exceptionally high for the time of year. Total reservoir storage decreased overall in April across Devon and Cornwall with Wimbleball, Colliford and Roadford reservoirs at 99%, 100% and 99% of net storage respectively at the end of the month.

2. Rainfall

Devon and Cornwall received 116mm of rain during April (167% of the April LTA), which is classed as notably high for the time of year. Rainfall was generally higher in western hydrological areas than eastern hydrological areas. Rainfall was notably high across most hydrological areas in April, except for the Otter, Sid, Axe and Lim hydrological area where rainfall was normal and the Taw and North Devon Streams, Exe, and Teign and Torbay hydrological areas where rainfall was above normal. Devon and Cornwall received most rainfall on 1 to 10 April and 26 to 30 April. The 7 month period from October 2023 (start of the water year) to April 2024 was the wettest on record, and this has been the wettest start to a calendar year (January to April) since records began in 1871.

3. Soil moisture deficit

Soil moisture deficit increased overall in April. On 30 April, the deficit was less than 10mm and was lower (soils were wetter) than the LTA for the time of year, and similar to the deficit at the same time in 2023.

4. River flows

April monthly mean river flows ranged from above normal to exceptionally high for the time of year across the area, with 7 out of the 13 reporting sites reporting exceptionally high mean river flows at over 200% of the monthly LTA for April. These 7 sites are located in the west of the area which reflects the notably high rainfall received there in April. Daily mean river flows fluctuated throughout the month in response to rainfall evens. On 30 April, all reporting sites in Cornwall recorded exceptionally high daily mean flows, and all reporting sites in Devon ranged from normal to exceptionally high daily mean flows for the time year.

Due to data accuracy concerns, Whitford is not reported on this month.

5. Groundwater levels   

Levels at 3 groundwater sites receded overall in April, with groundwater levels increasing overall at 3 sites. On 30 April, groundwater levels were notably high at Branscombe Lane (monitoring the Dawlish Sandstone Formation) and Woodleys No1 (monitoring the Otterton Sandstone Formation), and exceptionally high at all other reporting sites.

Due to data accuracy concerns, Winnards Perch (monitoring the Staddon Formation) is not reported on this month.

6. Reservoir stocks

Total reservoir storage decreased from 99% at the end of March to 98% at the end of April, ending the month higher than this time last year. At the end of the month, storage at Wimbleball, Colliford and Roadford reservoirs were 99%, 100% and 99% of net storage respectively, compared to 100%, 67% and 69% this time last year.

Author: Devon and Cornwall Hydrology, hydrology.dandc@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 within.