Research and analysis

Devon and Cornwall water situation: March 2024 summary

Updated 15 April 2024

Applies to England

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

1. Summary

Devon and Cornwall received 177% of the March long term average (LTA) rainfall, which was ‘exceptionally high’ for the time of year. Soil moisture deficit (SMD) remained close to 0mm in March and ended the month lower (wetter) than the LTA for the time of year. Monthly mean river flows ranged from ‘notably high’ to ‘exceptionally high’ for the time of year across all reporting stations. Levels at all reporting groundwater sites ended the month higher than the previous month. Total reservoir storage increased overall in March across Devon and Cornwall with Wimbleball, Colliford and Roadford reservoirs at 100%, 98% and 100% of net storage respectively at the end of the month.

2. Rainfall

Devon and Cornwall received 176mm of rain during March (177% of the March LTA), which is classed as ‘exceptionally high’ for the time of year. Rainfall was ‘exceptionally high’ across all hydrological areas in March, except the Taw and North Devon Streams, the Exe, Torridge and Hartland Streams and the Otter, Sid, Axe and Lim hydrological areas where rainfall was ‘notably high’ for the time of year. Devon and Cornwall received rainfall everyday throughout the month, with the highest quantities of rain falling on 4, 16 and 25 March. The 6-month cumulative rainfall total (October to March) for Devon and Cornwall was the second wettest 6-month period since records began in 1871.

3. Soil moisture deficit

Soil moisture deficit decreased overall in March but remained close to 0mm. On 26 March, 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

March monthly mean river flows ranged from ‘notably high’ to ‘exceptionally high’ for the time of year across the area,with Austins Bridge, Bodmin Dunmere, Gwills and Restormel all recording over 200% of the monthly LTA flow for March. Daily river flows fluctuated throughout the month in response to rainfall events. On 31 March, most reporting sites recorded ‘above normal’ to ‘notably high’ daily mean flows for the time of year, except for Bodmin Dunmere on the River Camel and Gwills on the river Gannel recording ‘exceptionally high’ daily mean flow for the time of year.

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

5. Groundwater levels   

Levels at all groundwater sites continued their recharge throughout March and all reporting site hydrographs are generally on their rising limbs, as would be expected this time of year. On 26 March, groundwater levels were ‘notably high’ at Branscombe Lane (monitoring the Dawlish Sandstone Formation) and Woodbury Common No2 (monitoring the Budleigh Salterton Pebble Beds) and ‘exceptionally high’ at all other reporting sites.

Due to missing data, Winnards Perch (monitoring the Staddon Formation) and Woodleys No1 (monitoring the Otterton Sandstone Formation) are not reported on this month.

6. Reservoir stocks

Total reservoir storage increased from 96% at the end of February to 99% at the end of March, ending the month higher than this time last year, and higher than the same time in 2022 (94%). At the end of the month, storage at Wimbleball, Colliford and Roadford reservoirs were 100%, 98% and 100% of net storage respectively, compared to 100%, 60% and 67% this time last year.

Author: Environment Agency, 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.