Water Situation Report South West Region

Monthly water situation report South West Region

Summary – December 2014 In contrast to December the previous year, the south west of England has experienced a dry December. Rainfall was 64% of the December long term average (LTA), making it the fifth month in 2014 that the two Areas have seen lower than average rainfall. Despite this, river flows have fluctuated throughout the month in response to rainfall events, though the majority of sites had ‘normal’ flows for the time of year at the end of December. Groundwater levels also remain ‘normal’ for the time of year at the majority of sites, though levels at some sites have receded. Soil moisture deficit decreased throughout December and is now close to zero in both Areas. Reservoir levels have increased over the month.

Rainfall Both Wessex and Devon and Cornwall Areas had below average rainfall for December with 59 mm (63%) and 90 mm (65%) respectively. Rainfall events were staggered throughout the month and occurred between the 9th and 11th, the 16th to the 18th and on the 26th of December. West Dorset Streams had the lowest rainfall total of 48 mm (50%) over the month, making it ‘notably low’ for the time of year. Whereas, the West Somerset Streams catchment received the highest total rainfall of 127 mm (96%), making it ‘normal’ for the time of year.

Soil Moisture Deficit Soil moisture deficit (SMD) decreased overall in December due to the occasional rainfall event. By the end of the month, SMD for both Areas was below 1 mm, which is normal for this time of year.

River Flows The majority of rivers in the south west of England had ‘normal’ monthly mean flows for the time of year. With a dry start to the month, many river flows declined but later increased in response to rainfall events. This resulted in more responsive rivers peaking at ‘notably high’ or ‘exceptionally high’ flows for the time of year, though these later subsided to ‘normal’ flows at the majority of sites by the end of the month.

Groundwater Levels Groundwater levels remain ‘normal’ for the time of year at the majority of sites, with some sites in North Wessex and East Devon ranging from ‘above normal’ to ‘exceptionally high’. The majority of groundwater sites remained in the same category throughout the month. The exceptions were Overcompton, Woodyates, and Woodleys No1 which, in response to the dry weather, returned to ‘normal’ levels for the time of year after being ‘above normal’. This decrease in levels also occurred at Bussels No7A, which is now ‘above normal’ for the time of year. The levels in rapid response boreholes such as Chantry No1 and Ashton Farm have already started to decline.

Reservoir Storage Reservoir storage has increased in December, despite the dry weather. South West Water’s total storage increased from 78% to 83%, Wessex Water’s increased from 78% to 88%, and Bristol Water’s increased from 74% to 84%.

Flood Warnings and Alerts Area Flood Warnings Flood Alerts Devon 0 14 Cornwall 2 (both were coastal) 3 Wessex North 0 15 (6 were coastal) Wessex South 0 1 (coastal)

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 2014

Sites Providing Stream Support River Site End of Month Status River Allen Wyke Down Off Chitterne Brook Codford Road On Gussage Stream Gussage All Saints Off Devil’s Brook Dewlish WDX Off River Piddle Briantspuddle Off South Winterbourne Winterbourne Abbas Off Pimperne Stream Pimperne Off Watergates Stream Watergates On River Wylye Brixton Deverill Off River Wylye Kingston Deverill Off Rodbourne Brook Lower Stanton St. Quinton Off Tetbury Avon Tetbury Off Sherston Avon Stanbridge Off Luckington Brook Luckington Off Gauze Brooke Hullavington Off Charlton Stream Charlton Off Chalfield Brook South Wraxall Off Chalfield Brook Little Chalfield Off

Abstraction Licences Subject to Cease or Restrict Catchment End of Month Status Hampshire Avon 1 cease, 1 restrict Dorset Frome 3 cease Stour -- Piddle -- Bride 1 restrict Wylye -- Bristol Avon -- Somerset --

Author: Hydrology and Water Resource Management Contact details: 07525 969024

Rainfall

Figure 1.1: Total rainfall for hydrological areas across South West England for the current month (up to December), the last three months and the last 12 months, classed relative to an analysis of respective historic totals. The values on the current month map are the percentage of the December long term average rainfall for each hydrological area. Produced using final and provisional NCIC (National Climate Information Centre) data (Source: Met Office © Crown Copyright). Crown copyright. All rights reserved. Environment Agency, 100026380, 2014.

Above 100% LTA rainfall Below 100% LTA rainfall

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

250%

200%

150%

100% Percentage of LTA

50% Apr Oct Apr Oct Jul Jul Jan 0% Jan ------13 14 - - 13 13 14 14 13 14

1-Month Period for South West - Wessex NCIC

250%

200%

150%

100% Percentage of LTA

50% Apr Oct Apr Oct Jul Jul 0% Jan Jan ------13 14 - - 13 13 14 14 13 14

Figure 1.2: Monthly rainfall totals as a percentage of the 1961 – 1990 long term average. Produced using final and provisional NCIC (National Climate Information Centre) data. (Source: Met Office © Crown Copyright, 2014).

Soil Moisture Deficit

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

Devon and Cornwall 0

100

Soil moisture deficit (mm) deficit moisture Soil 120

140

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

Wessex 0

100

Soil moisture deficit (mm) deficit moisture Soil 120

140

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

Figure 2.1: Latest soil moisture deficit compared to maximum, minimum, and 1961 – 1990 long term average. Weekly MORECS data for real land use (Source: Met Office © Crown Copyright, 2014).

River Flow

Figure 3.1: Monthly mean river flows at indicator sites for December 2014, expressed as a percentage of the respective long term average and classed relative to an analysis of historic December monthly means (Source: Environment Agency). Crown copyright. All rights reserved. Environment Agency, 100026380, 2014.

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Hayle at St Erth Camel at Denby Ranking derived from data for the period 03/01/1968 to 31/12/2012 Ranking derived from data for the period 31/08/1964 to 31/12/2012

5.0 35 December mean flow December mean flow 0.757 cumecs 7.612 cumecs 4.5 46% LTA 70% LTA 30 4.0

3.5 25

3.0 20 2.5 15 2.0

1.5 10

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

0.0 0 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data 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 December mean flow December mean flow 5.005 cumecs 33.766 cumecs 57% LTA 30 140 74% LTA

120 25

100 20 80 15 60

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

0 0 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15

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

120 140 December mean flow December mean flow 28.798 cumecs 33.114 cumecs 90% LTA 120 89% LTA 100

100 80

80 60 60

40 40

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

0 0 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15

Dart at Austins Bridge Exe at Thorverton Ranking derived from data for the period 30/09/1958 to 31/12/2012 Ranking derived from data for the period 30/04/1956 to 31/12/2012

100 December mean flow December mean flow 60 13.341 cumecs 90 30.84 cumecs 67% LTA 99% LTA 80 50 70

40 60

50 30 40

20 30

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

0 0 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15

Otter at Dotton Tone at Bishops Hull Ranking derived from data for the period 30/09/1962 to 31/12/2012 Ranking derived from data for the period 01/02/1961 to 31/12/2012

25 20 December mean flow December mean flow 3.5 cumecs 3.109 cumecs 18 61% LTA 67% LTA 20 16

15 12

10 8

5 4 Daily Mean Flow(cumecs) Daily Mean Flow(cumecs) 2

0 0 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Yeo at Pen Mill Upper Brue at Lovington Ranking derived from data for the period 31/10/1963 to 31/12/2012 Ranking derived from data for the period 01/10/1964 to 31/12/2012

25 14 December mean flow December mean flow 2.323 cumecs 2.405 cumecs 49% LTA 12 66% LTA 20

15 8

6 10

5 Daily Mean Flow(cumecs) Daily Mean Flow(cumecs) 2

0 0 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15

Bristol Avon at Bathford Somerset Frome at Tellisford Ranking derived from data for the period 27/10/1969 to 31/12/2012 Ranking derived from data for the period 01/09/1961 to 31/12/2012

140 25 December mean flow December mean flow 30.8 cumecs 4.635 cumecs 120 82% LTA 69% LTA 20

100

15 80

60 10

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

0 0 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15

Bristol Avon at Great Somerford Middle Stour at Hammoon Ranking derived from data for the period 16/12/1963 to 31/12/2012 Ranking derived from data for the period 01/03/1968 to 31/12/2012

25 60 December mean flow December mean flow 4.96 cumecs 6.849 cumecs 77% LTA 50% LTA 50 20

40 15

10 20

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

0 0 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15

Dorset Frome at East Stoke Combined Piddle at Baggs Mill Ranking derived from data for the period 01/01/1992 to 31/12/2012 Ranking derived from data for the period 01/01/1964 to 31/12/2012

25 December mean flow December mean flow 6.809 cumecs 14 2.878 cumecs 67% LTA 87% LTA 20 12

10 15 8

10 6

4 5 Daily Mean Flow(cumecs) Daily Mean Flow(cumecs) 2

0 0 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Wylye at South Newton Upper Hampshire Avon at Amesbury Ranking derived from data for the period 01/01/1967 to 31/12/2012 Ranking derived from data for the period 01/02/1965 to 31/12/2012

25 20 December mean flow December mean flow 3.491 cumecs 18 3.519 cumecs 70% LTA 81% LTA 20 16

15 12

10 8

5 4 Daily Mean Flow(cumecs) Daily Mean Flow(cumecs) 2

0 0 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15

Stour at Throop Lower Hampshire Avon at Knapp Mill Ranking derived from data for the period 01/01/1973 to 31/12/2012 Ranking derived from data for the period 01/01/1975 to 31/12/2012

80 120 December mean flow December mean flow 17.849 cumecs 21 cumecs 70 73% LTA 76% LTA 100

80 50

40 60

30 40

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

0 0 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15 28-Feb-14 30-Apr-14 30-Jun-14 31-Aug-14 31-Oct-14 31-Dec-14 28-Feb-15

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

Groundwater Levels

Figure 4.1: Groundwater levels for indicator sites at the end of December 2014, classed relative to an analysis of respective historic December 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, 2014.

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Allington No2 Ashton Farm Ranking derived from data for the period Oct-1974 to Dec-2012 Ranking derived from data for the period Feb-1974 to Dec-2012

82 72 80 71 78 70 76 69 74 68 72 67 70 66 Level (mAOD) Level (mAOD) Level 68 65 66 64 64 63 Mar-13 Jun-13 Sep-13 Dec-13 Mar-14 Jun-14 Sep-14 Dec-14 Mar-13 Jun-13 Sep-13 Dec-13 Mar-14 Jun-14 Sep-14 Dec-14

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data Chantry No1 Didmarton 1 Ranking derived from data for the period Feb-1974 to Dec-2012 Ranking derived from data for the period Nov-1975 to Dec-2012

156 98 154 93 88 152 83 150 78

148 73 Level (mAOD) Level (mAOD) Level 68 146 63 144 58 Mar-13 Jun-13 Sep-13 Dec-13 Mar-14 Jun-14 Sep-14 Dec-14 Mar-13 Jun-13 Sep-13 Dec-13 Mar-14 Jun-14 Sep-14 Dec-14 Overcompton Tilshead Ranking derived from data for the period Sep-1971 to Dec-2012 Ranking derived from data for the period Jan-1966 to Dec-2012

60 98 59 93 58

88 57 Level (mAOD) Level (mAOD) Level 56 83

55 78 Mar-13 Jun-13 Sep-13 Dec-13 Mar-14 Jun-14 Sep-14 Dec-14 Mar-13 Jun-13 Sep-13 Dec-13 Mar-14 Jun-14 Sep-14 Dec-14 Tilshead Borehole was artesian for January and February 2014 Woodyates Burrow Ranking derived from data for the period Jan-1942 to Dec-2012 Ranking derived from data for the period Jan-1969 to Dec-2012

37 102 36 97

92 35

87 34 82 33 Level (mAOD) Level Level (mAOD) Level 77 32 72

67 31 Mar-13 Jun-13 Sep-13 Dec-13 Mar-14 Jun-14 Sep-14 Dec-14 Mar-13 Jun-13 Sep-13 Dec-13 Mar-14 Jun-14 Sep-14 Dec-14 Bussels No7A Woodleys No1 Ranking derived from data for the period Nov-1971 to Dec-2012 Ranking derived from data for the period Jan-1966 to Dec-2012

26 34

33 25

24 Level (mAOD) Level (mAOD) Level 31

23 30 Mar-13 Jun-13 Sep-13 Dec-13 Mar-14 Jun-14 Sep-14 Dec-14 Mar-13 Jun-13 Sep-13 Dec-13 Mar-14 Jun-14 Sep-14 Dec-14

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, 2014).

Reservoir Stocks

── 2014 ── 2013 ── 1995 ── 1976 South West Water - Wimbleball South West Water - Colliford

100 100

80 80

60 60

40 40 Percentage oflive capacity Percentage oflive 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 South West Water - Roadford South West Water - Total Reservoir Storage

100 100

80 80

60 60

40 40 Percentage oflive capacity Percentage oflive 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 Wessex Water - Clatworthy Wessex Water - Sutton Bingham

100 100

80 80

60 60

40 40 Percentage oflive capacity Percentage oflive 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 Wessex Water - Total Reservoir Storage Bristol Water - Total Reservoir Storage

100 100

80 80

60 60

40 40 Percentage oflive capacity Percentage oflive 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 South West Region (Source: Water companies).

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).