Monthly Water Situation Report South East England

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Monthly water situation report South East England

Summary – August 2021 August was the first month since April when the rainfall recorded was below the long term average across the South-east of England. Only 88% of the LTA rainfall was recorded during the month, with the distribution of the rainfall skewed towards the first half of the month. The soil moisture deficits ended the month slightly below the average, and no significant recharge occurred. The rivers draining impermeable catchments responded to the heavy rainfall, with nearly half of the key indicator sites in the exceptionally high category. There were 16 fluvial flood alerts and 3 fluvial flood warnings. Levels fell at most of the groundwater sites during the month and remained at normal or higher levels.

Rainfall August was the first month since April when the rainfall recorded was below the long term average (LTA) across the South-east of England. Only 88% of the LTA rainfall was recorded during the month, with the distribution of the rainfall skewed towards the first half of the month, with the days with the highest totals the 1st, 6th, 8th, 9th and 21st. The highest daily total of 53.4mm was recorded at Westergate, Sussex Coast, Solent and South Downs (SSD) on the 8th August. Just under a half of this was recorded in 75 minutes. The heavy rainfall on the 8th formed a band from the Isle of Wight to Kent. By contrast, the distribution of the rain on the 21st was from the Cotswolds (Thames, THM) to the Chilterns (Hertfordshire and North London,HNL). On average, there were 19 ‘dry’ days (<0.2mm rainfall) across the South-east of England, half of which were at the end of the month.

Soil Moisture Deficit/Recharge Unsurprisingly the soil moisture deficits (SMDs) reflected the pattern of rainfall during the month, falling significantly in the south between the 6th and 8th and on the 21st across the Chilterns in the north. The SMDs increased during the dry weather after the 21st. Generally, the SMDs ended the month slightly below the LTA across the South east, although there were local variations. No significant recharge occurred during August.

River Flows The rivers draining impermeable catchments responded quickly to the heavy rainfall at the beginning of the month and declined very quickly. These daily peaks were high enough to affect the monthly average flows, resulting in nearly half of the indicator sites recording flows in the exceptionally high category. These included the Medway at Teston and East Farleigh (Kent and South London,KSL) and the Arun at Alfoldean (SSD). The Rother at Udiam (KSL) recorded the highest August flows on record. The groundwater-fed rivers were generally in the above normal category or higher and recorded the highest flows since 2014. The exceptions included the Wey at Tilford (THM) and the Ver at Colney Street (HNL) both with the highest flows since August 2001. There were 16 fluvial flood alerts and 3 fluvial flood warnings during August. HNL THM SSD KSL Total Fluvial Flood Alerts 0 3 9 4 16 Fluvial Flood Warnings 0 0 3 0 3 Groundwater Levels Groundwater levels across the South-east of England remained mainly at normal or above during the month. The exception was Jackaments (Oolites, THM) which was below normal. Levels for most of the Chilterns, Berkshire Downs and Hampshire Chalk remained in the normal range, including Stonor (THM) and Lopcombe (SSD). Levels for 14 of the 16 indicator boreholes fell during the month. However, the more responsive sites at Carisbrooke Castle (IOW) and Chilgrove (South Downs), both SSD, responded to the rainfall during the month and levels fell slightly to the record the highest August levels since 2012. West Meon (Hampshire Chalk, SSD) recorded the 3rd highest August level on record, the highest since 2007. About half of the key indicator sites had their highest levels since August 2014.

Reservoir Storage/Water Resource Zone Stocks Reservoir storage was above the LTA for all reservoirs with the exceptions of Darwell (KSL) and Farmoor (THM). Author: [email protected]

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.

www.gov.uk/environment-agency © Environment Agency 2021

Rainfall Map

Total rainfall for hydrological areas across South East England for the current month, the last 3 months, the last 6 months and the last 12 months classed relative to an analysis of respective historic totals. Data source:HadUK data based on the Met Office 1Km gridded rainfall dataset derived from raingauges. (Source:Met Office © Crown Copyright, 2021). Provisional data based on Environment Agency 1Km gridded rainfall dataset derived from Environment Agency intensity raingauges. Some features of this map are based on digital spatial data licensed from the Centre for Ecology and Hydrology, © CEH. Includes material based on Ordnance Survey 1:50 000 maps with the permission of the controller of Her Majesty’s Stationery Office © Crown copyright. All rights reserved. Environment Agency, 100026380, 2021.

www.gov.uk/environment-agency © Environment Agency 2021

River Flow and Groundwater Status Map

Groundwater site status based on end of month level. Surface water site status based on mean monthly flow.

Some features of this map are based on digital spatial data licensed from the Centre for Ecology and Hydrology, © CEH. Includes material based on Ordnance Survey 1:50 000 maps with the permission of the controller of Her Majesty’s Stationery Office © Crown copyright. All rights reserved. Environment Agency, 100026380, 2021

Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC

www.gov.uk/environment-agency © Environment Agency 2021

Thames – Page 1

Monthly total rainfall (mm) Long term average rainfall (mm) Cotswolds West - Rainfall Berkshire Downs - Rainfall 180 200

160 180

160 140 140 120 120 100 100 80 80 60

Rainfall (mm) Rainfall Rainfall (mm) Rainfall 40 40

20 20

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

Cotswolds West - Effective Rainfall Berkshire Downs - Effective Rainfall 160 120

140 100 120 80 100

80 60

60 40

40 Effective (mm) Effective Rainfall Effective (mm) Effective Rainfall 20 20

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

RIVER COLN AT BIBURY RIVER KENNET AT MARLBOROUGH Ranking used data from 01/10/1963 to 31/12/2017 Ranking used data from 01/02/1972 to 31/12/2017 7 5

4 6 4 5 3

4 3

3 2

2 2

1 Daily FlowMean (cumecs) Daily 1 FlowMean (cumecs) Daily 1

0 0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

RIVER THAMES AT FARMOOR (NATURALISED) Ranking used data from 01/10/1992 to 31/12/2017 80

20 Daily FlowMean (cumecs) Daily 10

0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

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Thames – Page 2

Monthly total rainfall (mm) Long term average rainfall (mm) North Downs Hampshire - Rainfall Wey Greensand - Rainfall 250 250

200 200

150 150

100 100

Rainfall (mm) Rainfall Rainfall (mm) Rainfall 50 50

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

North Downs Hampshire - Effective Rainfall Wey Greensand - Effective Rainfall 140 140

120 120

100 100

80 80

60 60

40 40 Effective (mm) Effective Rainfall 20 (mm) Effective Rainfall 20

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

RIVER WEY AT TILFORD RIVER LODDON AT SHEEPBRIDGE Ranking used data from 01/01/1973 to 31/12/2017 Ranking used data from 01/10/1965 to 31/12/2017 30 14

12 25

10 20

8 15 6

4 Daily FlowMean (cumecs) Daily 5 FlowMean (cumecs) Daily 2

0 0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

RIVER THAMES AT KINGSTON (NATURALISED) Ranking used data from 01/01/1951 to 31/12/2017 450

400

350

300

250

200

150

100 Daily FlowMean (cumecs) Daily 50

0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

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Hertfordshire and North London

Monthly total rainfall (mm) Long term average rainfall (mm) Chilterns East Colne - Rainfall Lee Chalk - Rainfall 200 180

180 160

160 140 140 120 120 100 100 80 80 60

Rainfall (mm) Rainfall Rainfall (mm) Rainfall 40 40

20 20

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

Chilterns East Colne - Effective Rainfall Lee Chalk - Effective Rainfall 120 100

90 100 80

70 80 60

60 50

40 40 30

20 Effective (mm) Effective Rainfall 20 (mm) Effective Rainfall 10

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

RIVER VER AT COLNEY STREET (HANSTEADS) RIVER MIMRAM AT PANSHANGER Ranking used data from 01/10/1956 to 31/12/2017 Ranking used data from 01/12/1952 to 31/12/2017 2.5 2.0

1.8

2.0 1.6

1.4

1.5 1.2

1.0

1.0 0.8

0.6

0.5 Installation 0.4 Daily FlowMean (cumecs) Daily of fish pass FlowMean (cumecs) Daily 0.2

0.0 0.0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

RIVER LEE AT FEILDES WEIR (NATURALISED) Ranking used data from 01/10/1883 to 31/12/2017 70

Daily FlowMean (cumecs) Daily 10

0 30-Oct-19 30-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

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Solent & South Downs – Page 1

Monthly total rainfall (mm) Long term average rainfall (mm) Test Chalk - Rainfall Lymington - Rainfall 250 250

200 200

150 150

100 100

Rainfall (mm) Rainfall Rainfall (mm) Rainfall 50 50

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

Test Chalk - Effective Rainfall Lymington - Effective Rainfall 120 160

140 100 120 80 100

60 80

60 40

40 Effective (mm) Effective Rainfall 20 (mm) Effective Rainfall 20

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

LYMINGTON RIVER AT BROCKENHURST RIVER TEST AT BROADLANDS Ranking used data from 01/01/1997 to 31/12/2017 Ranking used data from 01/10/1957 to 31/12/2017 14 35

12 30

10 25

8 20

6 15

4 10 Daily FlowMean (cumecs) Daily 2 FlowMean (cumecs) Daily 5

0 0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

RIVER ITCHEN AT ALLBROOK AND HIGHBRIDGE Ranking used data from 01/10/1958 to 31/12/2017 14

Daily FlowMean (cumecs) Daily 2

0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

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Solent & South Downs – Page 2

Monthly total rainfall (mm) Long term average rainfall (mm) Arun - Rainfall Ouse - Rainfall 200 250

180

160 200

140

120 150

100

80 100

Rainfall (mm) Rainfall Rainfall (mm) Rainfall 40 50

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

Arun - Effective Rainfall Ouse - Effective Rainfall 140 160

120 140

120 100

100 80 80 60 60

Effective (mm) Effective Rainfall Effective (mm) Effective Rainfall 20 20

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

RIVER ROTHER AT IPING MILL RIVER ARUN AT ALFOLDEAN Ranking used data from 01/11/1966 to 31/12/2017 Ranking used data from 01/05/1970 to 31/12/2017 25 35

30 20

15 20

15 10

5 Daily FlowMean (cumecs) Daily Daily FlowMean (cumecs) Daily 5

0 0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

RIVER OUSE AT GOLDBRIDGE Ranking used data from 01/03/1960 to 31/12/2017 35

Daily FlowMean (cumecs) Daily 5

0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

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Kent & South London – Page 1

Monthly total rainfall (mm) Long term average rainfall (mm) Medway - Rainfall Eastern Rother - Rainfall 200 200

180 180

160 160

140 140

120 120

100 100

80 80

60 60

Rainfall (mm) Rainfall Rainfall (mm) Rainfall 40 40

20 20

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

Medway - Effective Rainfall Eastern Rother - Effective Rainfall 140 160

120 140

120 100

100 80 80 60 60

Effective (mm) Effective Rainfall Effective (mm) Effective Rainfall 20 20

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

RIVER MEDWAY AT TESTON & EAST FARLEIGH COMBINED RIVER TEISE AT STONEBRIDGE Ranking used data from 01/10/1956 to 31/12/2017 Ranking used data from 01/10/1961 to 31/12/2017 160 30

140 25

120

20 100

80 15

60 10

40 Daily FlowMean (cumecs) Daily Daily FlowMean (cumecs) Daily 5 20

0 0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

RIVER ROTHER AT UDIAM Ranking used data from 01/10/1962 to 31/12/2017 60

Daily FlowMean (cumecs) Daily 10

0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

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Kent & South London – Page 2

Monthly total rainfall (mm) Long term average rainfall (mm) Darent - Rainfall Stour - Rainfall 180 180

160 160

140 140

120 120

100 100

80 80

60 60

Rainfall (mm) Rainfall Rainfall (mm) Rainfall 40 40

20 20

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

Darent - Effective Rainfall Stour - Effective Rainfall 160 160

140 140

120 120

100 100

80 80

60 60

40 40

Effective (mm) Effective Rainfall Effective (mm) Effective Rainfall 20 20

0 0

Sep-20 Sep-20

Oct-20 Oct-20

Nov-20 Nov-20

Dec-20 Dec-20

Jan-21 Jan-21

Feb-21 Feb-21

Mar-21 Mar-21

Apr-21 Apr-21

May-21 May-21

Jun-21 Jun-21

Jul-21 Jul-21 Aug-21 Aug-21

RIVER DARENT AT HAWLEY RIVER STOUR AT HORTON Ranking used data from 01/12/1963 to 31/12/2017 Ranking used data from 01/10/1964 to 31/12/2017 5 18

4 16

4 14

3 12

3 10

2 8

2 6

1 4

Daily FlowMean (cumecs) Daily Daily FlowMean (cumecs) Daily 1 2

0 0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

RIVER DOUR AT CRABBLE MILL Ranking used data from 06/01/1976 to 31/12/2017 1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4 Daily FlowMean (cumecs) Daily 0.2

0.0 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-20 31-Aug-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

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Groundwater Levels Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data JACKAMENTS BOTTOM STONOR PARK Ranking derived from data for the period Jan-1974 to Dec-2017 Ranking derived from data for the period May-1961 to Dec-2017

87 106

82 104

102 77

100 72

Level (mAOD) Level Level (mAOD) Level 67 96

94 62 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21

ROCKLEY OBH TILE BARN FARM Ranking derived from data for the period Mar-1933 to Dec-2017 Ranking derived from data for the period Oct-1971 to Dec-2017

146 95 144 94 142 93 92 140 91 138 90 136 89

134 Level (mAOD) Level Level (mAOD) Level 88 132 87 130 86 128 85 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21

ASHLEY GREEN STW OBH LILLEY BOTTOM OBH Ranking derived from data for the period Sep-1987 to Dec-2017 Ranking derived from data for the period Jul-1979 to Dec-2017

99 129 98

124 97

96 119

95 Level (mAOD) Level Level (mAOD) Level 94 114 93

109 92 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21

CLANVILLE GATE GWL LOPCOMBE CORNER GWL Ranking derived from data for the period Mar-1963 to Dec-2017 Ranking derived from data for the period Apr-1963 to Dec-2017

90 97 88 86 92 84 82 87

Level (mAOD) Level Level (mAOD) Level 78 82 76 74 77 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21

Groundwater Levels Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data CARISBROOKE CASTLE WEST MEON HUT GWL Ranking derived from data for the period Aug-1977 to Dec-2017 Ranking derived from data for the period Sep-1986 to Dec-2017

96 34 94 92 32 90 88 30 86 84

28 Level (mAOD) Level Level (mAOD) Level 82 26 80 78 24 76 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21

HOUNDEAN BOTTOM GWL CHIPSTEAD GWL Ranking derived from data for the period Jan-1977 to Dec-2017 Ranking derived from data for the period Oct-1942 to Dec-2017

105 29 103 24 101 99 19 97 14 95 93

9 Level (mAOD) Level Level (mAOD) Level 91 89 4 87 -1 85 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21

SWEEPS LANE LITTLE BUCKET FM Ranking derived from data for the period Jan-1984 to Dec-2017 Ranking derived from data for the period Jan-1971 to Dec-2017

46 87

46 82

45 77

45 72

44 67

Level (mAOD) Level Level (mAOD) Level

44 62

43 57 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21

RIDDLES LANE CHILGROVE HOUSE GWL Ranking derived from data for the period Apr-1982 to Dec-2017 Ranking derived from data for the period Feb-1836 to Dec-2017

75 27 70 25 65 23 60 21 19 55

17 50

Level (mAOD) Level Level (mAOD) Level 15 45 13 40 11 35 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21 Nov-19 Mar-20 Jul-20 Nov-20 Mar-21 Jul-21

Reservoir Stocks

2003 LTA MIN 2017 2018 2020 2021 2003 LTA MIN 2017 2018 2020 2021 Thames Water - Lower Thames Reservoirs - Lower Thames Thames Water - Lee Valley Reservoirs - Lower Lee 100 100

80 80

60 60

40 40

20 20

Percentage of live capacity oflive Percentage Percentage of live capacityof live Percentage

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

2003 LTA MIN 2017 2018 2020 2021 LTA MIN 2017 2018 2020 2021 Thames Water - Farmoor Reservoir - Upper Thames SES Water - Bough Beech Reservoir - Medway

100 100

80 80

60 60

40 40

20 20

Percentage of live capacityof live Percentage Percentage of live capacity oflive Percentage

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

LTA MIN 2017 2018 2020 2021 LTA MIN 2017 2018 2020 2021

South East Water - Ardingly Reservoir - Ouse South East Water - Arlington Reservoir - Cuckmere 100 100

80 80

60 60

40 40

20 20

Percentage of live capacityof live Percentage Percentage of live capacityof live Percentage

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

LTA MIN 2017 2018 2020 2021 LTA MIN 2017 2018 2020 2021 Southern Water - Bewl Reservoir - Teise (Medway) Southern Water - Darwell Reservoir - Rother (Eastern) 100 100 90 90 80 80 70 70 60 60 50 50 40 40 30 30

20 20 Percentage of live capacity oflive Percentage Percentage of live capacity oflive Percentage 10 10 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

LTA MIN 2017 2018 2020 2021 LTA MIN 2017 2018 2020 2021

Southern Water - Powdermill Reservoir - Brede Southern Water - Weir Wood Reservoir - Medway 100 100

80 80

60 60

40 40

20 20

Percentage of live capacityof live Percentage Percentage of live capacityof live Percentage

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

Cumulative Rainfall Plots

CUMULATIVE RAINFALL FOR THAMES AREA COMPARED WITH CUMULATIVE RAINFALL FOR HERTS AND NORTH LONDON AREA LONG TERM AVERAGE COMPARED WITH LONG TERM AVERAGE

2500 2500

2000 2000

1500 Average 1500 Average

1000 1000

Rainfall (mm) Rainfall Rainfall (mm) Rainfall

500 500

0 0

Jul-19 Jul-19

Jul-20 Jul-20

Jul-21 Jul-21

Oct-18 Oct-18

Apr-19 Apr-19

Oct-19 Oct-19

Apr-20 Apr-20

Oct-20 Oct-20

Apr-21 Apr-21

Jan-19 Jan-19

Jun-19 Jun-19

Jan-20 Jan-20

Jun-20 Jun-20

Jan-21 Jan-21

Jun-21 Jun-21

Mar-19 Mar-19

Mar-20 Mar-20

Mar-21 Mar-21

Feb-19 Feb-19

Feb-20 Feb-20

Feb-21 Feb-21

Dec-18 Dec-18

Nov-19 Nov-19

Dec-19 Dec-19

Nov-20 Nov-20

Dec-20 Dec-20

Aug-19 Aug-19

Sep-19 Sep-19

Aug-20 Aug-20

Sep-20 Sep-20

Aug-21 Aug-21

May-19 May-19

May-20 May-20 May-21 May-21 CUMULATIVE RAINFALL FOR SOLENT AND SOUTH DOWNS AREA CUMULATIVE RAINFALL FOR KENT AND SOUTH LONDON AREA COMPARED WITH LONG TERM AVERAGE COMPARED WITH LONG TERM AVERAGE

2500 2500

2000 2000

1500 Average 1500 Average

1000 1000

Rainfall (mm) Rainfall Rainfall (mm) Rainfall

500 500

0 0

Jul-19 Jul-19

Jul-20 Jul-20

Jul-21 Jul-21

Oct-18 Oct-18

Apr-19 Apr-19

Oct-19 Oct-19

Apr-20 Apr-20

Oct-20 Oct-20

Apr-21 Apr-21

Jan-19 Jan-19

Jun-19 Jun-19

Jan-20 Jan-20

Jun-20 Jun-20

Jan-21 Jan-21

Jun-21 Jun-21

Mar-19 Mar-19

Mar-20 Mar-20

Mar-21 Mar-21

Feb-19 Feb-19

Feb-20 Feb-20

Feb-21 Feb-21

Dec-18 Dec-18

Nov-19 Nov-19

Dec-19 Dec-19

Nov-20 Nov-20

Dec-20 Dec-20

Aug-19 Aug-19

Sep-19 Sep-19

Aug-20 Aug-20

Sep-20 Sep-20

Aug-21 Aug-21

May-19 May-19

May-20 May-20 May-21 May-21

South East Areal Rainfall units for reference

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).