Water Situation Report Devon and Cornwall Area

Monthly water situation report Devon and Cornwall Area

Summary – November 2018 An average of 200 mm of rainfall fell across Devon and Cornwall in November, which is 160% of the long term average (LTA). There were several heavy rainfall events across the month. Monthly mean river flows ranged from ‘normal’ to ‘above normal’ across Devon and Cornwall. Groundwater levels continued to recede with the exception of Bussels No7A, and SMD dropped to 3 mm. Overall, reservoir storage increased from to 50% to 58%.

Rainfall An average of 200 mm of rainfall fell across Devon and Cornwall in November, which is 160% of the LTA for the month and is ‘above normal’ for the time of year. There were several rainfall events, the heaviest being around 6 – 9 November, and the end of the month. Rainfall ranged between 215% LTA (Otter, Sid, Axe and Lim), and 105% LTA (Taw and North Devon Streams). Rainfall maps and graph

Soil Moisture Deficit The soil moisture deficit had an overall drop over the month. At month end it was at 3 mm which is now equal to the LTA for the time of year. SMD graph and map

River Flows Monthly mean river flows ranged from ‘normal’ to ‘above normal’ across Devon and Cornwall. Five rivers had ‘above normal’ flows and 9 had ‘normal’ flows.’ Rivers showed marked changes with the rainfall this month, with many reaching ‘exceptionally high’ flows around 9 November, and nearly all rivers then reaching ‘below normal’ levels in the third week of November. The end of November saw a rise again to high levels including ‘exceptionally high’ levels. This is due to the rivers in Devon and Cornwall being ‘flashy’ and quickly reactive to rainfall. River flow map and graphs

Groundwater Levels Groundwater levels continued to recede in November with the exception of Bussels No7A which is starting to show recovery. All stations are at ‘normal’ levels for the time of year, apart from Woodleys No1 which is ‘below normal’. Groundwater map and graphs

Reservoir Storage Overall, total reservoir storage rose from 50% in October to 58% across Devon and Cornwall. Wimbleball storage rose to 45%, Colliford rose to 58% and Roadford rose to 50% total storage. Reservoir graphs

Author: Devon, Cornwall and the Isle 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 2018

Rainfall

Figure 1.1: Total rainfall for hydrological areas across Devon and Cornwall for the current month (up to November), the last three months, the last six months and the last 12 months, classed relative to an analysis of respective historic totals. Final NCIC (National Climate Information Centre) data based on the Met Office 5km gridded rainfall dataset derived from rain gauges (Source: Met Office © Crown Copyright, 2018). 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, 2018.

www.gov.uk/environment-agency © Environment Agency 2018

Above 100% LTA rainfall Below 100% LTA rainfall

1-Month Period for South West - Devon & Cornwall NCIC

250%

200%

150%

100% Percentage LTAof Percentage

50%

0% Dec-16 Jan-17 Feb-17 Mar-17 Apr-17 May-17 Jun-17 Jul-17 Aug-17 Sep-17 Oct-17 Nov-17 Dec-17 Jan-18 Feb-18 Mar-18 Apr-18 May-18 Jun-18 Jul-18 Aug-18 Sep-18 Oct-18 Nov-18

Figure 1.2: Monthly rainfall totals as a percentage of the 1961 – 1990 long term average. Final NCIC (National Climate Information Centre) data based on the Met Office 5km gridded rainfall dataset derived from rain gauges (Source: Met Office © Crown Copyright, 2018). 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, 2018.

Soil Moisture Deficit

Less than historic minimum Greater than historic maximum ..... 1961-1990 long term average ── Latest data ── 2017

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, 2018).

www.gov.uk/environment-agency © Environment Agency 2018

Month-end Soil Moisture Deficit (mm)

Figure 2.2: Soil moisture deficits for week ending 27 November 2018. MORECS data for real land use (Source: Met Office © Crown Copyright, 2018). Crown copyright. All rights reserved. Environment Agency, 100026380, 2018.

www.gov.uk/environment-agency © Environment Agency 2018

River Flow

Figure 3.1: Monthly mean river flows at indicator sites for November 2018, expressed as a percentage of the respective long term average and classed relative to an analysis of historic November monthly means (Source: Environment Agency). Crown copyright. All rights reserved. Environment Agency, 100026380, 2018.

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Hayle at St Erth Kenwyn at Truro Ranking derived from data for the period 03/01/1968 to 31/12/2012 Ranking derived from data for the period 31/10/1968 to 31/12/2012

5.0 2.0 November mean flow November mean flow 4.5 0.702 cumecs 1.8 0.484 cumecs 66% LTA 95% LTA 4.0 1.6

3.5 1.4

3.0 1.2

2.5 1.0

2.0 0.8

1.5 0.6

1.0 0.4 Daily Mean Flow (cumecs) Daily Mean Flow (cumecs) 0.5 0.2

0.0 0.0 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18

www.gov.uk/environment-agency © Environment Agency 2018

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Gannel at Gwills Camel at Denby Ranking derived from data for the period 01/12/1969 to 31/12/2012 Ranking derived from data for the period 31/08/1964 to 31/12/2012

4.0 35 November mean November mean flow flow 9.94 cumecs 3.5 0.895 cumecs 30 114% LTA

3.0 25

2.5 20 2.0 15 1.5

10 1.0 Daily Mean Flow (cumecs) Daily Mean Flow (cumecs) 0.5 5

0.0 0 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18

Fowey at Restormel Tamar at Gunnislake Ranking derived from data for the period 31/03/1961 to 31/12/2012 Ranking derived from data for the period 25/06/1956 to 31/12/2012

35 160 November mean flow November mean flow 7.82 cumecs 42.8 cumecs 140 30 114% LTA 115% LTA

120 25

100 20 80 15 60

10 40 Daily Mean Flow (cumecs) Daily Mean Flow (cumecs) 5 20

0 0 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18

Torridge at Torrington Taw at Umberleigh Ranking derived from data for the period 31/07/1960 to 31/12/2012 Ranking derived from data for the period 30/09/1958 to 31/12/2012

140 140 November mean flow November mean 22.9 cumecs flow 120 84% LTA 120 19.4 cumecs 64% LTA

100 100

80 80

60 60

40 40

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

0 0 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18

East Dart at Bellever Dart at Austins Bridge Ranking derived from data for the period 31/03/1964 to 31/12/2012 Ranking derived from data for the period 30/09/1958 to 31/12/2012

10 November mean flow November mean flow 60 9 2.56 cumecs 24.3 cumecs 143% LTA 63% LTA 8 50 7

6 40

5 30 4

3 20

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

0 0 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18

www.gov.uk/environment-agency © Environment Agency 2018

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Teign at Chudleigh Bridge Exe at Thorverton Ranking derived from data for the period 01/01/1958 to 31/12/2012 Ranking derived from data for the period 30/04/1956 to 31/12/2012

50.0 100 November mean flow November mean 45.0 11.2 cumecs 90 flow 135% LTA 15.5 cumecs 40.0 80 152% LTA

35.0 70

30.0 60

25.0 50

20.0 40

15.0 30

10.0 20 Daily Mean Flow (cumecs) Daily Mean Flow (cumecs) 5.0 10

0.0 0 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18

Otter at Dotton Axe at Whitford Ranking derived from data for the period 30/09/1962 to 31/12/2012 Ranking derived from data for the period 05/11/1964 to 31/12/2012

25 40 November mean flow November mean flow 5.86 cumecs 10.4 cumecs 35 139% LTA 140% LTA 20 30

25 15

10 15

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

0 0 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18 30-Jan-18 30-Mar-18 30-May-18 30-Jul-18 30-Sep-18 30-Nov-18

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 2018

Groundwater Levels

Figure 4.1: Groundwater levels for indicator sites at the end of November 2018, classed relative to an analysis of respective historic November 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, 2018.

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data WHITLANDS BUSSELS NO7A Ranking derived from data for the period Sep-1984 to Dec-2012 Ranking derived from data for the period Nov-1971 to Dec-2012

89 26

88 25

87 24 Level (mAOD) Level (mAOD) Level

87 24

86 23 Feb-16 Jun-16 Oct-16 Feb-17 Jun-17 Oct-17 Feb-18 Jun-18 Oct-18 Feb-16 Jun-16 Oct-16 Feb-17 Jun-17 Oct-17 Feb-18 Jun-18 Oct-18

www.gov.uk/environment-agency © Environment Agency 2018

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data WOODLEYS NO1 BRANSCOMBE LANE Ranking derived from data for the period Jan-1966 to Dec-2012 Ranking derived from data for the period May-1987 to Dec-2012

34 21

34 20 33 19 33 18 32 17 32 Level (mAOD) Level Level (mAOD) Level 16 31

31 15

30 14 Feb-16 Jun-16 Oct-16 Feb-17 Jun-17 Oct-17 Feb-18 Jun-18 Oct-18 Feb-16 Jun-16 Oct-16 Feb-17 Jun-17 Oct-17 Feb-18 Jun-18 Oct-18

WOODBURY COMMON NO2 Ranking derived from data for the period Nov-1967 to Dec-2012

103 103 102 102 101 101 100

Level (mAOD) Level 100 99 99 98 Feb-16 Jun-16 Oct-16 Feb-17 Jun-17 Oct-17 Feb-18 Jun-18 Oct-18

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, 2018).

Reservoir Stocks

── 2018 ── 2017 ── 1995 ..... 100% live capacity South West Water - Colliford South West Water - Roadford

100 100

80 80

60 60

40 40 Percentage of live capacity Percentage of live capacity 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

Reservoir Stocks

── 2018 ── 2017 ── 1995 ..... 100% live capacity South West Water - Wimbleball South West Water - Total Reservoir Storage

100 100

80 80

60 60

40 40 Percentage of live capacity Percentage of live capacity 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