Research and analysis

Devon and Cornwall water situation: July 2024 summary

Updated 14 August 2024

Applies to England

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

1. Summary

Devon and Cornwall received 163% of the long term average (LTA) rainfall, which was above normal for the time of year. It was the wettest October to July period in a record starting in 1871. Soil moisture deficit (SMD) decreased overall in July and ended the month lower (wetter) than the LTA for the time of year. Monthly mean river flows ranged from normal to notably high for the time of year across the area. Groundwater levels at all sites receded overall in July, but still ended the month at normal to exceptionally high for the time of year. Total reservoir storage across Devon and Cornwall ended the month at 84% net storage, with Wimbleball, Colliford and Roadford reservoirs at 77%, 85% and 91% of net storage respectively at the end of July.

2. Rainfall

Devon and Cornwall received 114mm of rain during July (163% of the July LTA), which is classed as above normal for the time of year. It was the wettest October to July period in a record starting in 1871, with all hydrological catchments ranking within the top 5 wettest 10-month periods, in a record starting 1871. The most significant periods of rain occurred on 4 to 8 July, 12 to 15 July and 19 to 25 July, with very little rain in the remainder of the month.

In July, rainfall was above normal for the time of year in most hydrological areas apart from the Torridge and Hartland Streams, the Exe and the Taw and North Devon Streams hydrological areas where rainfall was normal for the time of year. In the last 6 and 12 months, cumulative rainfall totals were exceptionally high in all hydrological areas when compared to historic respective totals. In the last 3 months, cumulative rainfall totals were normal in all hydrological areas, except for the Otter, Sid, Axe and Lim, where cumulative rainfall was notably high for the time of year.

3. Soil moisture deficit

Soil moisture deficit decreased (soils became wetter) overall in July. By 30 July, the average deficit for Devon & Cornwall was 11 to 70mm and was lower (soils were wetter) than the LTA for the time of year. The SMD was slightly higher (soils were drier) than the same time in 2023.

4. River flows

July monthly mean river flows were normal for the time of year across most sites. The Dart at Austins Bridge, East Dart at Bellever, Teign at Chudleigh Bridge and Otter on the River Dotton all recorded above normal monthly mean river flow for the time of year. Whitford on the River Axe recorded notably high monthly mean river flows for the time of year. All reporting stations experienced a downward trend in daily mean river flows towards the end of the month in response to the decreased rainfall. On 31 July, all reporting sites recorded normal or above normal daily mean flows for the time of year.

Due to missing data and accuracy concerns, Truro gauging station on the River Kenwyn excludes dates between 25 to 31 July.

5. Groundwater levels        

Levels at all groundwater sites receded overall in July. On 31 July, groundwater levels were exceptionally high at the following sites:

• Branscombe Lane (monitoring the Dawlish Sandstone)
• Bussells No7A (monitoring the Dawlish Sandstone)
• Whitlands (monitoring the Upper Greensand)
• Woodbury Common No2 (monitoring the Budleigh Salterton Pebble Beds)

Levels at Winnards Perch (monitoring the Staddon Formation) were classed as normal, levels at Woodleys No1 (monitoring the Otterton Sandstone Formation) were classed as above normal and levels at Coleford Production (monitoring the Permian Breccias and Sandstones) were classed as notably high respectively on 31 July.

6. Reservoir stocks

Total reservoir storage was 84% at the end of July, which is a reduction of 5% of storage since the end of June. This is higher than total storage at the same time last year and in 2022.  At the end of the month, storage at Wimbleball, Colliford and Roadford reservoirs was 77%, 85% and 91% of net storage respectively, compared to 75%, 57% and 57% 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.