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Monthly water situation report East Anglia Summary – May 2017 In contrast to the previous 10 months May was wetter than average. Soil moisture deficits have returned to normal but groundwater continued to fall with most sites classified as below normal. Groundwater fed rivers are mainly classified as below normal but in runoff dominated catchments flows have returned to normal. Reservoirs are near their normal operating curves.

Rainfall After a dry start to the month a series of bands of rain during the middle of the month meant that May was wetter than the long term average in East Anglia. The area received an average of 55mm of rainfall, 114% of the long term average for May. The wettest part of the area was South Essex with 68mm, 159% of the long term average and the driest was North Norfolk with 50mm, 101% of the long term average.

Soil Moisture Deficit/Recharge In response to the wet May the soil moisture deficit has returned to normal for the time of year with an average value of 64mm in the area.

River Flows Despite the wet weather flows continued to fall at most sites with only the more runoff dominated sites showing an increase. Of the 17 sites reported on 5 are classified as normal, mainly in the clay catchments, 11 are classified as below normal, these are in the groundwater dominated catchments and the River Cam at Dernford is classified as exceptionally low.

Groundwater Levels Groundwater levels have continued to fall at all sites but in response to recent rainfall some sites are showing a shallower decline. Of the 16 sites used in this month’s report 5 are classified as normal, 9 below normal and the remaining 2 are classified as notably low.

Reservoir Storage/Water Resource Zone Stocks Reservoir stocks are near their normal operating curves.

Forward Look Probabilistic ensemble projections for river flows at key sites September 2017: There is an increased probability of flows being below the normal range in most of the chalk catchments this September. December 2017: There is an increased probability of flows being below the normal range at most sites in December. Probabilistic ensemble projections for groundwater levels in key aquifers September 2017: In the south of the area there is a greatly increased probability of Therfield Rectory and Redlands being notably low. In the rest of the area the model is forecasting levels on the boundary between normal and below normal for most rainfall scenarios. March 2018: The long range nature of these projections mean the models are currently showing a spread of results, however there is a tendency for the sights to the south to show an increased probability of levels below the normal range.

Author:

Hydrology & Operations

Contact details: 03708506506

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 2016

Rainfall

May 2017

© Environment Agency 2017

200%

200%

150%

150%

100%

100%

50%

50%

0%

0%

May-17

May-17

May-17

May-17

0%

Jun-16

Jul-16

Aug-16

Sep-16

Oct-16

Nov-16

Dec-16

Jan-17

Feb-17

Mar-17

Apr-17

May-17

Jun-16

Jul-16

Aug-16

Sep-16

Oct-16

Nov-16

Dec-16

Jan-17

Feb-17

Mar-17

0%

Feb-17

50%

Jan-17

50%

Dec-16

100%

Nov-16

100%

Oct-16

150%

Sep-16

150%

Aug-16

200%

Jul-16

Jun-16

May-17

Apr-17

Mar-17

Feb-17

Jan-17

Dec-16

Nov-16

Oct-16

Sep-16

Aug-16

Jul-16

Jun-16

200%

Mar-17

Apr-17

0%

Mar-17

0%

Feb-17

50%

Jan-17

50%

Dec-16

100%

Nov-16

100%

Oct-16

150%

Sep-16

150%

Aug-16

200%

Jul-16

Jun-16

May-17

Apr-17

Mar-17

Feb-17

Jan-17

Dec-16

Nov-16

Oct-16

Sep-16

Aug-16

Jul-16

Jun-16

200%

Mar-17

0%

Feb-17

0%

Jan-17

50%

Dec-16

50%

Nov-16

100%

Oct-16

100%

Sep-16

150%

Aug-16

150%

Jul-16

Jun-16

May-17

Apr-17

Mar-17

Feb-17

Jan-17

Dec-16

Nov-16

200%

Apr-17

1-Month Period for North Norfolk 250% 1-Month Period for Little Ouse and Lark 250%

Oct-16

Sep-16

Aug-16

Jul-16

Jun-16

200%

Apr-17

1-Month Period for NW Norfolk and Wissey 250% 1-Month Period for Cam 250%

Below average rainfall Above average rainfall

Apr-17

1-Month Period for Central Area Fenland 250% 1-Month Period for Lower Bedford Ouse 250%

1-Month Period for Upper Bedford Ouse 250%

1-Month Period for East Anglia 250%

© Environment Agency 2017

Above average rainfall

Below average rainfall

1-Month Period for Broadland Rivers

250%

200%

200%

150%

150%

100%

100%

50%

50%

0%

0%

May-17

Jan-17

Dec-16

Nov-16

Oct-16

Sep-16

Aug-16

Jul-16

Jun-16

May-17

Apr-17

Mar-17

Feb-17

Jan-17

Dec-16

Nov-16

Oct-16

Sep-16

Aug-16

Jul-16

Jun-16

May-17

0% Apr-17

0%

Apr-17

50%

Mar-17

50%

Mar-17

100%

Feb-17

100%

Feb-17

150%

Jan-17

150%

Dec-16

200%

Nov-16

1-Month Period for South Essex

250%

200%

Oct-16

Sep-16

Aug-16

Jul-16

Jun-16

May-17

Apr-17

Mar-17

Feb-17

Jan-17

Dec-16

Nov-16

Oct-16

Sep-16

Aug-16

Jul-16

Jun-16

1-Month Period for North Essex

250%

1-Month Period for East Suffolk

250%

Soil Moisture Deficit

© Environment Agency 2017

Data based on MORECS dataset (Met Office © Crown Copyright)

───2015-16 Exceptionally high Below normal

─ ─ ─2014-15 Notably high Notably low

Above normal Exceptionally low

Normal ─── Latest data

East Anglia Ranking derived from data for the period Jan-1961 to Dec-2012 0 20

SMD (mm)

40 60 80

100 120 140 Aug Sep Oct Nov Dec Jan Feb Mar

River Flow

Apr May Jun

Jul

May 2017

© Environment Agency 2017

Exceptionally high Below normal

Notably high Notably low

Above normal Exceptionally low

Normal ─── Latest data

Cappenham, TOVE Ranking derived from data for the period Feb-1962 to Dec-2012 6.0

Flow (cumecs)

5.0 4.0

3.0 2.0 1.0 0.0 Aug-16

Oct-16

Dec-16

Feb-17

Apr-17

Jun-17

Willen, OUZEL

Roxton, OUSE (AN)

Ranking derived from data for the period Jan-1962 to Dec-2012

Ranking derived from data for the period Oct-1972 to Dec-2012

16

50

12

Flow (cumecs)

Flow (cumecs)

14

10 8 6

40 30 20

4 10 2 Oct-16

Dec-16

Feb-17

Apr-17

0 Aug-16

Jun-17

Oct-16

Dec-16

Feb-17

Apr-17

Jun-17

Blunham, IVEL

Offord(Gross Flows), OUSE (AN)

Ranking derived from data for the period Aug-1959 to Dec-2012

Ranking derived from data for the period Jan-1970 to Dec-2012

12

120

10

100

Flow (cumecs)

Flow (cumecs)

0 Aug-16

8

6 4 2 0 Aug-16

80

60 40 20

Oct-16

Dec-16

Feb-17

Apr-17

Jun-17

0 Aug-16

Oct-16

Dec-16

Feb-17

Apr-17

Jun-17

© Environment Agency 2017

Notably high Notably low

Above normal Exceptionally low

Normal ─── Latest data

Dernford, CAM (AN)

Temple, LARK

Ranking derived from data for the period Feb-1949 to Dec-2012

Ranking derived from data for the period Nov-1960 to Dec-2012

5.0

5.0

4.5

4.5

4.0

4.0

3.5

3.5

Flow (cumecs)

Flow (cumecs)

Exceptionally high Below normal

3.0 2.5 2.0 1.5

3.0 2.5 2.0 1.5

1.0

1.0

0.5

0.5

0.0 Aug-16

Oct-16

Dec-16

Feb-17

Apr-17

0.0 Aug-16

Jun-17

Oct-16

Dec-16

Feb-17

Apr-17

Jun-17

Abbey Heath, LITTLE OUSE

Northwold Total, WISSEY

Ranking derived from data for the period Jun-1968 to Dec-2012

Ranking derived from data for the period Jul-1983 to Dec-2012 8

16 7

12

Flow (cumecs)

Flow (cumecs)

14

10 8 6

6

5 4 3

4

2

2

1

0 Aug-16

Oct-16

Dec-16

Feb-17

Apr-17

0 Aug-16

Jun-17

Oct-16

Dec-16

Feb-17

Apr-17

Jun-17

Denver Ely Ouse, OUSE (AN)

Marham, NAR

Ranking derived from data for the period Nov-1971 to Dec-2012

Ranking derived from data for the period Apr-1982 to Dec-2012 3.0 2.5

40

Flow (cumecs)

Flow (cumecs)

50

30 20 10 0 Aug-16

2.0

1.5 1.0 0.5

Oct-16

Dec-16

Feb-17

Apr-17

0.0 Aug-16

Jun-17

Oct-16

Dec-16

Feb-17

Apr-17

Jun-17

Heacham, HEACHAM

Ingworth, BURE

Ranking derived from data for the period Nov-1965 to Dec-2012

Ranking derived from data for the period Jun-1959 to Dec-2012

1.0

3.0

0.9 2.5

0.7

Flow (cumecs)

Flow (cumecs)

0.8

0.6 0.5 0.4 0.3 0.2

2.0

1.5 1.0 0.5

0.1 0.0 Aug-16

Oct-16

Dec-16

Feb-17

Apr-17

Jun-17

0.0 Aug-16

Oct-16

Dec-16

Feb-17

Apr-17

Jun-17

© Environment Agency 2017

Exceptionally high Below normal

Notably high Notably low

Above normal Exceptionally low

Normal ─── Latest data

Swanton Morley Total Flow, WENSUM

Needham Weir Total, WAVENEY LOWER

Ranking derived from data for the period Oct-1969 to Dec-2012

Ranking derived from data for the period Dec-1963 to Dec-2012

10

12

9

10

7

Flow (cumecs)

Flow (cumecs)

8

6 5 4 3 2

Oct-16

Dec-16

Feb-17

Apr-17

4

0 Aug-16

Jun-17

Oct-16

Dec-16

Feb-17

Apr-17

Jun-17

Lexden, COLNE (AN)

Springfield, CHELMER

Ranking derived from data for the period Oct-1959 to Dec-2012

Ranking derived from data for the period Nov-1965 to Dec-2012

7

6

6

5

5

Flow (cumecs)

Flow (cumecs)

6

2

1 0 Aug-16

8

4

3 2

3 2 1

1 0 Aug-16

4

Oct-16

Dec-16

Feb-17

Apr-17

Jun-17

0 Aug-16

Oct-16

Dec-16

Feb-17

Apr-17

Jun-17

© Environment Agency 2017

Groundwater Levels

Notably high Notably low

Above normal Exceptionally low

Normal ─── Latest data

FRINGFORD - GREAT OOLITE

BIGGLESWADE

Ranking derived from data for the period Sep-1980 to Dec-2012

Ranking derived from data for the period Mar-1968 to Dec-2012

99

28.0

98

27.5

97 96 95

Level (mAOD)

Level (mAOD)

Exceptionally high Below normal

May 2017

27.0 26.5 26.0

94

25.5

93 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

25.0 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

© Environment Agency 2017

Exceptionally high Below normal

Notably high Notably low

Above normal Exceptionally low

Normal ─── Latest data

THERFIELD RECTORY

REDLANDS HALL

Ranking derived from data for the period Jan-1883 to Dec-2012

Ranking derived from data for the period Aug-1963 to Dec-2012

96 52

Level (mAOD)

86 81

47

42

76

37

71 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

32 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

LINTON

GOG MAGOG

Ranking derived from data for the period Jan-1980 to Dec-2012

Ranking derived from data for the period Jan-1980 to Dec-2012

31

18

30

17

29

Level (mAOD)

Level (mAOD)

Level (mAOD)

91

28 27

26

16 15 14

25

13

24 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

12 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

BURY ST EDMUNDS

NEWMARKET

Ranking derived from data for the period May-1983 to Dec-2012

Ranking derived from data for the period Feb-1983 to Dec-2012

33

17 16

31

Level (mAOD)

Level (mAOD)

32

30 29 28 27

15 14 13

26

25 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

12 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

KENNINGHALL

BRECKLAND

Ranking derived from data for the period Aug-1973 to Dec-2012

Ranking derived from data for the period Jan-1971 to Dec-2012

33

29

32

28

30 29 28 27 26

Level (mAOD)

Level (mAOD)

31 27 26 25

24

25 24

23 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

23

22 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

© Environment Agency 2017

Exceptionally high Below normal

Notably high Notably low

Above normal Exceptionally low

Normal ─── Latest data

WASHPIT FARM ROUGHAM

BIRCHAM TOFTS

Ranking derived from data for the period May-1950 to Dec-2012

Ranking derived from data for the period Sep-1971 to Dec-2012

50 50

49

48

47

Level (mAOD)

Level (mAOD)

48 46 45 44 43 42

46 44 42 40

41

40 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

38 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

SMEETHAM HALL COTT.

CASTLE FARM

Ranking derived from data for the period Jan-1964 to Dec-2012

Ranking derived from data for the period Mar-1967 to Dec-2012

30.0

24

29.5 22

29.0

Level (mAOD)

Level (mAOD)

28.5 28.0 27.5 27.0 26.5 26.0

20 18 16 14

25.5

25.0 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

12 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

OLD PRIMARY SCHOOL, South Creake

PUG COTTAGE

Ranking derived from data for the period Sep-1952 to Dec-2012

Ranking derived from data for the period Feb-1991 to Dec-2012

24

2.0 1.8

23

Level (mAOD)

Level (mAOD)

1.6 22 21 20

19

1.4 1.2 1.0 0.8 0.6 0.4

18

0.2

17 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

0.0 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

THE SPINNEY Ranking derived from data for the period Nov-1952 to Dec-2012

12.0 11.5

Level (mAOD)

11.0

10.5 10.0 9.5 9.0 8.5

8.0 Aug-14 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17

© Environment Agency 2017

Reservoir Stocks

───2015-2016

May 2017

───Normal Operating Curve

───Drought Alert Curve

Alton

100

100

90

90

Percentage of live capacity

Percentage of live capacity

Grafham

── ─1995-1996

80 70 60 50 40 30 20 10

80 70 60 50 40 30 20 10

0

0 Jan Mar May

Jul

Sep Nov Jan Mar May

Jul

Sep Nov

Jan Mar May

Jul

Sep Nov Jan Mar May

Jul

Sep Nov

© Environment Agency 2017

───2015-2016

───Normal Operating Curve

───Drought Alert Curve

Ardleigh

Abberton

100

100

90

Percentage of live capacity

Percentage of live capacity

── ─1995-1996

80 70 60 50 40 30 20

80

60

40

20 Control curve 1 Control curve 2

10

n.b. from 20/01/2014 Abberton %full is based on increased “19m.Volume” n.b. from 29/09/2014 Abberton %full is based on increased “20m.Volume”

0

0 Jan Mar May

Jul

Sep Nov Jan Mar May

Jul

Sep Nov

Jul

Sep Nov

Jan Mar May

Jul

Sep Nov Jan Mar May

Jul

Sep Nov

Hanningfield

Percentage of live capacity

100 90 80 70 60 50 40 30 20

Control curve

10 0 Jan Mar May

Jul

Sep Nov Jan Mar May

© Environment Agency 2017

Forward Look – River Flows

Exceptionally high or low levels are those which would typically occur 5% of the time within the historic record. Notably high or low levels are those which would typically occur 8% of the time. Above normal or below normal levels are those which would typically occur 15% of the time. Normal levels are those which would typically occur 44% of the time within the historic record.

Probabilistic ensemble projections of river flows at key indicator sites in September 2017. Pie charts indicate probability, based on climatology, of the surface water flow at each site being e.g. exceptionally low for the time of year. (Source: Centre for Ecology and Hydrology, Environment Agency) Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC. Crown copyright. All rights reserved. Environment Agency, 100026380, 2017. ^ “Naturalised” flows are projected for these sites’

© Environment Agency 2017

Exceptionally high or low levels are those which would typically occur 5% of the time within the historic record. Notably high or low levels are those which would typically occur 8% of the time. Above normal or below normal levels are those which would typically occur 15% of the time. Normal levels are those which would typically occur 44% of the time within the historic record.

Probabilistic ensemble projections of river flows at key indicator sites in December 2017. Pie charts indicate probability, based on climatology, of the surface water flow at each site being e.g. exceptionally low for the time of year. (Source: Centre for Ecology and Hydrology, Environment Agency) Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC. Crown copyright. All rights reserved. Environment Agency, 100026380, 2017. ^ “Naturalised” flows are projected for these sites’

© Environment Agency 2017

Forward Look - Groundwater

Exceptionally high or low levels are those which would typically occur 5% of the time within the historic record. Notably high or low levels are those which would typically occur 8% of the time. Above normal or below normal levels are those which would typically occur 15% of the time. Normal levels are those which would typically occur 44% of the time within the historic record.

Probabilistic ensemble projections of groundwater levels at key indicator sites for end of September 2017. Pie charts indicate probability, based on climatology, of the groundwater level at each site being e.g. exceptionally low for the time of year. (Source: Environment Agency) Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC. Crown copyright. All rights reserved. Environment Agency, 100026380, 2017.

© Environment Agency 2017

Exceptionally high or low levels are those which would typically occur 5% of the time within the historic record. Notably high or low levels are those which would typically occur 8% of the time. Above normal or below normal levels are those which would typically occur 15% of the time. Normal levels are those which would typically occur 44% of the time within the historic record.

Probabilistic ensemble projections of groundwater levels at key indicator sites for end of March 2017. Pie charts indicate probability, based on climatology, of the groundwater level at each site being e.g. exceptionally low for the time of year. (Source: Environment Agency) Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC. Crown copyright. All rights reserved. Environment Agency, 100026380, 2016.

© Environment Agency 2017

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 (m 3s-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 Notably high Above normal Normal Below normal Notably low Exceptionally low

Value likely to fall within this band 5% of the time Value likely to fall within this band 8% of the time Value likely to fall within this band 15% of the time Value likely to fall within this band 44% of the time Value likely to fall within this band 15% of the time Value likely to fall within this band 8% of the time Value likely to fall within this band 5% of the time

© Environment Agency 2017