Research and analysis

Devon and Cornwall water situation: October 2024 summary

Updated 13 November 2024

Applies to England

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

1. Summary

Devon and Cornwall received 130% of the October long term average (LTA) rainfall, which was normal for the time of year. Soil moisture deficit (SMD) decreased overall in October and ended the month lower (wetter) than the LTA for the time of year. Monthly mean river flows ranged from normal to exceptionally high for the time of year across the area. Groundwater levels at most sites are just beginning their seasonal rise, or are showing signs of being about to do so, and ended the month at normal to exceptionally high for the time of year. Total reservoir storage across Devon and Cornwall ended the month at 80% net storage, with Wimbleball, Colliford and Roadford reservoirs at 69%, 71%, and 88% of net storage respectively at the end of October.

2. Rainfall

Devon and Cornwall received 152mm of rain during October (130% of the October LTA), which is classed as normal for the time of year. The most significant periods of rain occurred on 5 to 8 October and 13 to 19 October, with some dry spells mainly occurring at the beginning and end of the month. October was the 18th month out of the previous 24 months to have experienced wetter than average rainfall.

In October, rainfall was normal in most hydrological areas except for the Exe and the Otter, Sid, Axe and Lim where rainfall was above normal for the time of year. In the last 3 months, cumulative rainfall totals were normal in 8 reporting catchments, above normal in the Exe and North Cornwall catchments, and notably high in the Otter, Sid, Axe and Lim catchment, for the time of year. Cumulative rainfall over the last 12 months has been exceptionally high.

3. Soil moisture deficit

SMD decreased (soils became wetter) overall in October. By 15 October the average deficit for Devon and Cornwall was below 1mm, and 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 October, SMD was similar to the same time in 2023.

4. River flows

October monthly mean river flows ranged between normal to exceptionally high for the time of year. Dotton on the River Otter recorded exceptionally high monthly mean river flows, while Whitford on the River Axe and Bodmin Dunmere on the River Camel recorded notably high monthly river flows, reflecting higher rainfall in these catchments. All reporting stations experienced peaks in daily mean river flow in the middle of the month in response to increased rainfall, with a downward trend toward the end of the month. On 31 October, all reporting sites recorded normal daily mean flows, with the exception of St Erth on the River Hayle which recorded above normal daily mean flows for the time of year.

Due to data accuracy concerns, we have low confidence in the data at Truro gauging station on the River Kenwyn and St Erth gauging station on the River Hayle towards the end of October.

5. Groundwater levels   

On 31 October, 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 Bussels No7A (monitoring the Dawlish Sandstone) and Woodleys No1 (monitoring the Otterton Sandstone Formation)
• above normal at Coleford Production (monitoring the Permian Breccias and Sandstones)
• normal at Winnards Perch (monitoring the Staddon Formation)

Bussels No7A and Coleford Production hydrographs have just begun their seasonal rising limbs. Levels at all other sites except Branscombe Lane are flattening out, indicating they are about to begin rising.

6. Reservoir stocks

Total reservoir storage was 80% at the end of October, which is an increase of 8% in storage since the end of September. 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 69%, 71% and 88% of net storage respectively, compared to 83%, 52% and 55% this time last year.

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.