Monthly water situation report Devon and Cornwall Area Summary – August 2021 Devon and Cornwall received 56 mm of rainfall in August, which is 66% of the Long Term Average rainfall (LTA) and ‘below normal’ for the time of year. Most catchments received ‘below normal’ rainfall this month. Monthly mean river flows were mostly ‘normal’ for the time of year. Soil moisture deficit increased. Groundwater levels remained healthy overall, and reservoir storage decreased as is normal for this time of year. Rainfall Devon and Cornwall received 56 mm of rainfall in August, which is 66% of the LTA rainfall and ‘below normal’ for the time of year. All rainfall catchments across the area had ‘below normal’ rainfall apart from the Otter, Sid, Axe and Lim catchment, which was ‘normal’ for the time of year. There were rainfall events around 5-9 August and 20-21 August. Rainfall maps and graph Rainfall catchments map Soil Moisture Deficit Soil moisture deficit (SMD) for Devon and Cornwall increased to 50 mm at the end of the month, close to the LTA of 52 mm. At the end of the month, soils were wetter than average for the time of year in the east of the area, and drier than average in the west of the area, reflecting the higher rainfall in the east. SMD graph and map River Flows Monthly mean flows were ‘normal’ for the time of year everywhere except the Otter at Dotton and the Kenwyn at Truro, where flows were ‘above normal’ for the time of year. Daily mean flows generally receded through the month, responding slightly to the rainfall around 7 August and 21 August. At the end of August daily mean flows were nearly all ‘normal’ with only the Hayle at St Erth and the Torridge at Torrington recording ‘below normal’ flows. River flow map and graphs Groundwater Levels The indicator groundwater sites ranged from ‘normal’ to ‘above normal’ for this time of year. Groundwater levels receded very slightly this month, but overall levels remained stable. Please note that there is missing data for Woodbury Common 2 this month. Groundwater map and graphs Reservoir Storage Total reservoir storage decreased from 86% at the end of July to 80% at the end of August. Storage at Wimbleball decreased to 81%, Colliford decreased to 69% and Roadford decreased to 84%. This is as expected at this time of year. Reservoir graphs Glossary Author: Hydrology Devon, Cornwall and the Isles of Scilly Contact details: 020302 52532 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 herein. © Environment Agency 2021 Rainfall Figure 1.1: Total rainfall for hydrological areas across Devon and Cornwall for the current month (up to August), the last three months, the last six months and the last 12 months, classed relative to an analysis of respective historic totals. HadUK data based on the Met Office 5km gridded rainfall dataset derived from rain gauges (Source: Met Office © Crown Copyright, 2021). Provisional data based on Environment Agency 1km gridded rainfall dataset derived from Environment Agency intensity rain gauges. Crown copyright. All rights reserved. Environment Agency, 100026380, 2021. www.gov.uk/environment-agency © Environment Agency 2021 Above 100% LTA rainfall Below 100% LTA rainfall 1-Month Period for Devon and Cornwall 250% 200% 150% 100% 50% Dec-19 Jan-20 Feb-20 Mar-20 Apr-20 May-20 Jun-20 Jul-20 Dec-20 Jan-21 Feb-21 Mar-21 Apr-21 May-21 Jun-21 Jul-21 0% Sep-19 Oct-19 Nov-19 Aug-20 Sep-20 Oct-20 Nov-20 Aug-21 Figure 1.2: Monthly rainfall totals as a percentage of the 1961 – 1990 long term average. Final HadUK data based on the Met Office 5km gridded rainfall dataset derived from rain gauges (Source: Met Office © Crown Copyright, 2021). Provisional data based on Environment Agency 1km gridded rainfall dataset derived from Environment Agency intensity rain gauges. Crown copyright. All rights reserved. Environment Agency, 100026380, 2021. Soil Moisture Deficit Less than historic minimum Greater than historic maximum ..... 1961-1990 long term average ── Latest data ── 2020 0 20 40 60 80 100 Soil moisture deficit(mm) 120 140 160 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 2.1: Latest soil moisture deficit compared to previous year, maximum, minimum and 1961 – 1990 long term average. Weekly MORECS data for real land use (Source: Met Office © Crown Copyright, 2021). www.gov.uk/environment-agency © Environment Agency 2021 Month-end Soil Moisture Deficit (mm) Figure 2.2: Soil moisture deficits for week ending 31 August 2021. MORECS data for real land use (Source: Met Office © Crown Copyright, 2021). Crown copyright. All rights reserved. Environment Agency, 100026380, 2021. www.gov.uk/environment-agency © Environment Agency 2021 River Flow Figure 3.1: Monthly mean river flows at indicator sites for August 2021, expressed as a percentage of the respective long term average and classed relative to an analysis of historic August monthly means (Source: Environment Agency). Crown copyright. All rights reserved. Environment Agency, 100026380, 2021. Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data ST ERTH, River Hayle TRURO, River Kenwyn Ranking used data from 03/01/1968 to 31/12/2017 Ranking used data from 31/10/1968 to 31/12/2017 8 3 August mean flow August mean flow .3 cumecs 7 .1 cumecs 76% LTA 3 113% LTA 6 2 5 4 2 3 1 2 Daily Mean Flow (cumecs) Daily Mean Flow (cumecs) 1 1 0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 www.gov.uk/environment-agency © Environment Agency 2021 Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data GWILLS, River Gannel BODMIN DUNMERE, River Camel Ranking used data from 01/12/1969 to 31/12/2017 Ranking used data from 01/01/1965 to 31/12/2017 6 40 August mean flow August mean flow .2 cumecs 1.2 cumecs 95% LTA 35 72% LTA 5 30 4 25 3 20 15 2 10 Daily Mean Flow (cumecs) 1 Daily Mean Flow (cumecs) 5 0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 RESTORMEL, River Fowey GUNNISLAKE, River Tamar Ranking used data from 31/03/1961 to 31/12/2017 Ranking used data from 25/06/1956 to 31/12/2017 70 300 August mean flow August mean flow 1.4 cumecs 5.1 cumecs 60 65% LTA 250 60% LTA 50 200 40 150 30 100 20 Daily Mean Flow (cumecs) Daily Mean Flow (cumecs) 50 10 0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 TORRINGTON, River Torridge UMBERLEIGH, River Taw Ranking used data from 31/07/1960 to 31/12/2017 Ranking used data from 30/09/1958 to 31/12/2017 180 180 August mean flow August mean flow 160 2.3 cumecs 160 4.7 cumecs 44% LTA 80% LTA 140 140 120 120 100 100 80 80 60 60 40 40 Daily Mean Flow (cumecs) Daily Mean Flow (cumecs) 20 20 0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 BELLEVER, East Dart River AUSTINS BRIDGE, River Dart Ranking used data from 31/03/1964 to 31/12/2017 Ranking used data from 30/09/1958 to 31/12/2017 25 200 August mean flow August mean flow .7 cumecs 180 5.0 cumecs 104% LTA 102% LTA 20 160 140 15 120 100 10 80 60 5 40 Daily Mean Flow (cumecs) Daily Mean Flow (cumecs) 20 0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 www.gov.uk/environment-agency © Environment Agency 2021 Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data CHUDLEIGH BRIDGE, River Teign THORVERTON, River Exe Ranking used data from 17/02/1990 to 31/12/2017 Ranking used data from 30/04/1956 to 31/12/2017 70 160 August mean flow August mean flow 1.2 cumecs 140 6.4 cumecs 60 82% LTA 102% LTA 120 50 100 40 80 30 60 20 40 Daily Mean Flow (cumecs) Daily Mean Flow (cumecs) 10 20 0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 DOTTON, River Otter WHITFORD, River Axe Ranking used data from 30/09/1962 to 31/12/2017 Ranking used data from 06/11/1964 to 31/12/2017 35 90 August mean flow August mean flow 1.8 cumecs 80 2.3 cumecs 30 115% LTA 96% LTA 70 25 60 20 50 15 40 30 10 20 Daily Mean Flow (cumecs) 5 Daily Mean Flow (cumecs) 10 0 0 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 31-Oct-20 31-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 31-Aug-21 31-Oct-21 Figure 3.2: Indicator river flow sites for Devon and Cornwall.