Water Situation Report Devon and Cornwall Area

Monthly water situation report Devon and Cornwall Area

Summary – August 2019 An average of 109 mm of rainfall fell across Devon and Cornwall in August, which is 127% of the long term average (LTA). Catchments received ‘Above normal’ or ‘Normal’ rainfall for August. Monthly mean river flows ranged from ‘Above normal’ to ‘Below normal’ across Devon and Cornwall. Groundwater levels have seen very little change during August, and SMD was 62 mm at the end of the month. Reservoir storage dropped to 64%.

Rainfall An average of 109 mm of rainfall fell across Devon and Cornwall in August, which is 127% of the LTA for the month and is ‘Normal’ for the time of year. Two catchments received ‘Above normal’ rainfall for the month, while the rest received ‘Normal’ rainfall. Rainfall ranged between 118% LTA (West Cornwall, and Taw and Devon Streams), and 139% LTA (Teign and Torbay).

Rainfall maps and graph

Soil Moisture Deficit The soil moisture at the beginning of August was around 83mm before dropping to 46 mm by the middle of the month, and rising to 62mm towards the end of the month. This was higher than the LTA of 53 mm for that week.

SMD graph and map

River Flows Monthly mean river flows recorded from ‘Above normal’ to ‘Below normal’ for this time of year across Devon and Cornwall for August. Which means most rivers have risen from last month with the exception of Chudleigh Bridge which remains ‘Below normal’, and Thorverton, Umberleigh and Truro still ‘Normal’.

River flow map and graphs

Groundwater Levels There has been very little change to all groundwater levels during August. Four stations recorded ‘Normal’ levels and three ‘Below normal’ levels.

Groundwater map and graphs

Reservoir Storage Overall, the total reservoir storage for Devon and Cornwall dropped from 68% at the beginning of July to 64% at the end of the month. Wimbleball storage dropped to 79%, Colliford dropped to 58%, and Roadford dropped to 52% total storage.

Reservoir graphs

Glossary

Author: Devon, Cornwall and the Isles of Scilly Hydrology Team Contact details: 03708 506506

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 2019

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, 2019). 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, 2019.

www.gov.uk/environment-agency © Environment Agency 2019

Above 100% LTA rainfall Below 100% LTA rainfall 1-Month Period for Devon and Cornwall

250%

200%

150%

100%

50%

Oct-17 Mar-18 Jul-18 Dec-18 Sep-17 Nov-17 Dec-17 Jan-18 Feb-18 Apr-18 May-18 Jun-18 Aug-18 Sep-18 Oct-18 Nov-18 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19

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, 2019). 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, 2019.

Soil Moisture Deficit

Less than historic minimum Greater than historic maximum ..... 1961-1990 long term average ── Latest data ── 2018

100

Soil moisture deficit (mm) deficit Soilmoisture 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, 2019).

www.gov.uk/environment-agency © Environment Agency 2019

Month-end Soil Moisture Deficit (mm)

Figure 2.2: Soil moisture deficits for week ending 31 August 2019. MORECS data for real land use (Source: Met Office © Crown Copyright, 2019). Crown copyright. All rights reserved. Environment Agency, 100026380, 2019.

www.gov.uk/environment-agency © Environment Agency 2019

River Flow

Figure 3.1: Monthly mean river flows at indicator sites for August 2019, 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, 2019.

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 5 3 August mean flow August mean flow 4 0.301 cumecs 0.108 cumecs 79% LTA 3 97% LTA 4

3 2

3 2 2

2 1

1 Daily Flow(cumecs) Mean Daily Daily Flow(cumecs) Mean Daily 1 1

0 0 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19

www.gov.uk/environment-agency © Environment Agency 2019

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 5 30

August mean flow August mean flow 4 0.246 cumecs 1.02 cumecs 122% LTA 25 60% LTA 4

3 20

3 15 2

2 10

1 Daily Flow(cumecs) Mean Daily Daily Flow(cumecs) Mean Daily 5 1

0 0 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19

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 25 160 August mean flow August mean flow 1.34 cumecs 140 4.84 cumecs 64% LTA 57% LTA 20 120

100 15

10 60

Daily Flow(cumecs) Mean Daily Flow(cumecs) Mean Daily 20

0 0 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19

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 160 140 August mean flow August mean flow 140 2.9 cumecs 3.68 cumecs 55% LTA 120 63% LTA

120 100

100 80 80 60 60

Daily Flow(cumecs) Mean Daily Flow(cumecs) Mean Daily 20 20

0 0 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19

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 10 90 August mean flow August mean flow 9 0.993 cumecs 80 5.93 cumecs 153% LTA 122% LTA 8 70 7 60 6 50 5 40 4 30 3 20

Daily Flow(cumecs) Mean Daily Flow(cumecs) Mean Daily 1 10

0 0 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19

www.gov.uk/environment-agency © Environment Agency 2019

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 17/02/2004 to 31/12/2017 Ranking used data from 30/04/1956 to 31/12/2017

50 100 August mean flow August mean flow 45 1.54 cumecs 90 6.37 cumecs 24% LTA 101% LTA 40 80

35 70

30 60

25 50

20 40

15 30

10 20

Daily Flow(cumecs) Mean Daily Flow(cumecs) Mean Daily 5 10

0 0 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19

DOTTON, River Otter WHITFORD, River Axe Ranking used data from 30/09/1962 to 31/12/2017 Ranking used data from 05/11/1964 to 31/12/2017 25 60 August mean flow August mean flow 1.54 cumecs 1.92 cumecs 99% LTA 50 79% LTA 20

40 15

10 20

5 Daily Flow(cumecs) Mean Daily Daily Flow(cumecs) Mean Daily 10

0 0 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19 31-Oct-18 31-Dec-18 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19

Figure 3.2: Indicator river flow sites for Devon and Cornwall. Daily mean flow compared to an analysis of historic daily mean flows. (Source: Environment Agency).

www.gov.uk/environment-agency © Environment Agency 2019

Groundwater Levels

Figure 4.1: Groundwater levels for indicator sites at the end of August 2019 classed relative to an analysis of respective historic August levels (Source: Environment Agency). Geological map reproduced with permission from UK Groundwater Forum, BGS © NERC. Note: groundwater levels are reported at different times during the month and therefore may not be fully representative of levels at the month end. Crown copyright. All rights reserved. Environment Agency, 100026380, 2019.

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data WOODLEYS NO1 WOODBURY COMMON NO2 Ranking derived from data for the period Jan-1966 to Dec-2017 Ranking derived from data for the period Nov-1967 to Dec-2017

34 103

34 103 102 33 102 33 101 32 101

32 100 Level (mAOD) Level Level (mAOD) Level 100 31 99 31 99 30 98 Nov-16 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-16 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19

www.gov.uk/environment-agency © Environment Agency 2019

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data BUSSELS NO7A WHITLANDS Ranking derived from data for the period Nov-1971 to Dec-2017 Ranking derived from data for the period Sep-1984 to Dec-2017

26 89

25 88

24 87

Level (mAOD) Level (mAOD) Level

24 87

23 86 Nov-16 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-16 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19

BRANSCOMBE LANE WINNARDS PERCH B.H. Ranking derived from data for the period May-1987 to Dec-2017 Ranking derived from data for the period Jan-2002 to Dec-2017

22 134

21 133 20 132 19

18 131

130 Level (mAOD) Level Level (mAOD) Level 16 129 15

14 128 Nov-16 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-16 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19

COLEFORD PRODUCTION Ranking derived from data for the period Jan-1998 to Dec-2017

95 Level (mAOD) Level

93 Nov-16 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19

Figure 4.2: Indicator groundwater level sites for major aquifers. End of month groundwater levels compared to analysis of historic end month levels (Source: Environment Agency, 2019).

Reservoir Stocks

── 2019 ── 2018 ── 1995 ..... 100% live capacity South West Water - Colliford South West Water - Roadford

100 100

80 80

60 60

40 Percentage of live capacity of Percentage live Percentage of live capacity of Percentage live 20 20

0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec South West Water - Wimbleball South West Water - Total Reservoir Storage

100 100

80 80

60 60

40 40

Percentage of live capacity of Percentage live capacity of Percentage live 20 20

0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Figure 5.1: Reservoir stocks in Devon and Cornwall (Source: South West Water).

Glossary

Term Definition

Aquifer A geological formation able to store and transmit water.

Areal average rainfall The estimated average depth of rainfall over a defined area. Expressed in depth of water (mm).

Artesian The condition where the groundwater level is above ground surface but is prevented from rising to this level by an overlying continuous low permeability layer, such as clay.

Artesian borehole Borehole where the level of groundwater is above the top of the borehole and groundwater flows out of the borehole when unsealed.

Cumecs Cubic metres per second (m3s-1)

Effective rainfall The rainfall available to percolate into the soil or produce river flow. Expressed in depth of water (mm).

Flood Alert/Flood Warning Three levels of warnings may be issued by the Environment Agency. Flood Alerts indicate flooding is possible. Flood Warnings indicate flooding is expected. Severe Flood Warnings indicate severe flooding.

Groundwater The water found in an aquifer.

Long term average (LTA) The arithmetic mean calculated from the historic record, usually based on the period 1961-1990. However, the period used may vary by parameter being reported on (see figure captions for details). mAOD Metres Above Ordnance Datum (mean sea level at Newlyn Cornwall).

MORECS Met Office Rainfall and Evaporation Calculation System. Met Office service providing real time calculation of evapotranspiration, soil moisture deficit and effective rainfall on a 40 x 40 km grid.

Naturalised flow River flow with the impacts of artificial influences removed. Artificial influences may include abstractions, discharges, transfers, augmentation and impoundments.

NCIC National Climate Information Centre. NCIC area monthly rainfall totals are derived using the Met Office 5 km gridded dataset, which uses rain gauge observations.

Recharge The process of increasing the water stored in the saturated zone of an aquifer. Expressed in depth of water (mm).

Reservoir gross capacity The total capacity of a reservoir.

Reservoir live capacity The capacity of the reservoir that is normally usable for storage to meet established reservoir operating requirements. This excludes any capacity not available for use (e.g. storage held back for emergency services, operating agreements or physical restrictions). May also be referred to as ‘net’ or ‘deployable’ capacity.

Soil moisture deficit (SMD) The difference between the amount of water actually in the soil and the amount of water the soil can hold. Expressed in depth of water (mm).

Categories Exceptionally high Value likely to fall within this band 5% of the time Notably high Value likely to fall within this band 8% of the time Above normal Value likely to fall within this band 15% of the time Normal Value likely to fall within this band 44% of the time Below normal Value likely to fall within this band 15% of the time Notably low Value likely to fall within this band 8% of the time

Exceptionally low Value likely to fall within this band 5% of the time

Rainfall Catchments