Research and analysis

Devon and Cornwall water situation: November 2024 summary

Updated 13 December 2024

Applies to England

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

1. Summary

Devon and Cornwall received 120% of the November long term average (LTA) rainfall, which was normal for the time of year. Soil moisture deficit (SMD) decreased overall in November and ended the month lower (wetter) than the LTA for the time of year. Monthly mean river flows ranged from normal to above normal for the time of year across the area. Groundwater levels at most sites are just beginning their seasonal rise, and ended the month at between normal and exceptionally high for the time of year. Total reservoir storage across Devon and Cornwall ended the month at 86% net storage, with Wimbleball, Colliford and Roadford reservoirs at 78%, 76%, and 92% of net storage respectively at the end of November.

2. Rainfall

Devon and Cornwall received 152mm of rain during November (120% of the November LTA), which is classed as normal for the time of year. The most significant periods of rain occurred between 17 November and 26 November and on the 29 November and 30 November, with very little rainfall occurring at the beginning of the month. November was the ninth month out of the past 12 months to have experienced above average rainfall.

In November, rainfall was normal in most hydrological areas except for the Teign and Torbay and Avon Dart and Erme hydrological areas, where rainfall was above normal for the time of year. Cumulative rainfall in the last 12 months has been exceptionally high.

3. Soil moisture deficit

SMD decreased (soils became wetter) overall in November. By 19 November the average deficit for Devon and Cornwall was below 10mm. SMD remained at this level for the remainder of the month, meaning the average deficit was lower (soils were wetter) than the LTA for the time of year. By the end of November, SMD was similar to the same time in 2023.

We have recently updated our SMD maps and now report on SMD across our key river catchments. SMD was less than 10mm across the catchment on 4 December which is within 5mm of the LTA for the whole of the area expect in the Otter, Sid, Axe and Lym catchments where SMD is 6mm to 25mm lower (wetter) than the LTA for the time of year for that catchment.

4. River flows

November monthly mean river flows ranged between normal to above normal for the time of year. Bellever, on the East Dart, Chudleigh Bridge on the River Teign, Dotton on the River Otter and Whitford on the River Axe all recorded above normal monthly mean flows, reflecting higher rainfall in these catchments. All reporting stations experienced peaks in daily mean river flow towards the end of the month, following 21 November in response to rainfall associated with Storm Bert. On 30 November, all reporting sites recorded normal to notably high daily mean flows for the time of year.

5. Groundwater levels   

On 30 November, groundwater levels were classed as follows:

• exceptionally high at Branscombe Lane (monitoring the Dawlish Sandstone), Whitlands (monitoring the Upper Greensand), and Woodbury Common No2 (monitoring the Budleigh Salterton Pebble Beds)
• notably high at Coleford Production (monitoring the Permian Breccias and Sandstones) and Woodleys No1 (monitoring the Otterton Sandstone Formation)
• above normal at Bussels No7A (monitoring the Dawlish Sandstone)
• normal at Winnards Perch (monitoring the Staddon Formation)

All groundwater sites hydrographs have just begun their seasonal rising limbs.

6. Reservoir stocks

Total reservoir storage was 86% at the end of November, which is an increase of 7% in storage since the end of October. This is higher than the total storage at the same time last year and in 2022. At the end of the month, storage at Wimbleball, Colliford and Roadford was 78%, 76% and 92% of net storage respectively, compared to 100%, 62% and 67% this time last year.

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.