Water Situation Report Solent and South Downs Area

Monthly water situation report Solent and South Downs Area

Summary – December 2019 Solent and South Downs had above average rainfall for December with 166% of the long term average (LTA). The soil moisture deficits ended the month at zero. River flows ranged from above normal to exceptionally high. Groundwater levels ranged from below normal to exceptionally high. End of month reservoir stocks were above average at both Ardingly and Arlington Reservoirs.

Rainfall Solent and South Downs (SSD) had above average rainfall for December, receiving 166% (146mm) of the LTA (88mm). Rain this month was generally distributed fairly evenly across SSD, with all areal units receiving between 130-167mm. However, in relation to areal LTAs, the east (excluding the Pevensey Levels) was slightly wetter. The Lymington areal unit received the lowest rainfall total for the month (153% LTA) whilst the highest monthly total was recorded in the Adur areal unit (171% LTA). The highest daily total across the area of 34.2mm was recorded on the 19th at Ardingly (Ouse catchment). All five of the highest daily totals were recorded on the 19th in Sussex. There were no completely dry days for the whole area, but more significant rainfall events (of over 10mm) were confined to the middle of the month (10th - 21st). The September to December four month total across SSD of 504mm was the wettest since 2002 (505mm).

Soil Moisture Deficit/Recharge Soil moisture deficits across Solent and South Downs remained at zero throughout the month.

River Flows Monthly mean river flows across SSD ranged from above normal to exceptionally high. Chilbolton GS (Test), Blackwater GS (Medina), North Fareham (Wallington) and Brockenhurst (Lymington) all recorded above normal flows. Monthly mean flows were notably high at Mislingford (Meon), Allbrook & Highbridge (Itchen), Broadlands (Test) and Iping Mill (Western Rother). Cowbeech (Cuckmere), Sakeham (Adur), Alfoldean (Arun), and Goldbridge (Ouse) all recorded exceptionally high mean monthly flow.

Groundwater Levels End of month groundwater levels ranged from below normal to exceptionally high. Boreholes at Alverstone and Harting Common have just started to show a response to the wet weather, but remain below normal for December. Only Catherington recorded normal groundwater levels. Beeding Hill, Lopcombe Corner and West Meon Hut were all in the notably high range, in addition to Cornish Farm -- showing a dramatic response to above average wet weather - which recorded its fifth highest December level after being below normal in November. Groundwater levels at Chilgrove House, Houndean Bottom, and Carisbrooke Castle were all exceptionally high with both Houndean Bottom and Carisbrooke Castle recording 2nd highest levels since records began at these sites in 1977.

Reservoir Storage/Water Resource Zone Stocks End of month reservoir stocks were above average at Ardingly Reservoir (Ouse Catchment) with 100% of total capacity (LTA 87%) and at Arlington Reservoir (Cuckmere catchment) with 98% of total capacity (LTA 87%).

Environmental Impact During December 16 Flood Warnings and 35 Flood Alerts were issued (5 of the alerts for groundwater flooding). 14 of the Flood Warnings and 18 of the Flood Alerts were issued in Sussex, where it was slightly wetter and catchments are faster to respond than those in Hampshire and the Isle of Wight. At the start of December, there were three licences restricted due to insufficient flow in the River Test. At the end of the month no licences were restricted.

Author: HydrologySSD

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 2019

Rainfall Map 1

Total rainfall for hydrological areas across Solent and South Downs for the current month, classed relative to an analysis of respective historic totals. Provisional data based on Environment Agency 1km gridded rainfall dataset derived from Environment Agency intensity rain gauges. 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, 2019.

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

Rainfall Map 2

Total rainfall for hydrological areas across Solent and South Downs for the current month (up to 31 December), the last 3 months, the last 6 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, 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

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, 2019 Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC

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

West Hampshire – Page 1

Monthly total rainfall (mm) Long term average rainfall (mm) Test Chalk - Rainfall Lymington - Rainfall 160 160

140 140

120 120

100 100

80 80

60 60

Rainfall(mm) 40 Rainfall(mm) 40

20 20

0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19

Test Chalk - Effective Rainfall Lymington - Effective Rainfall 160 160

140 140

120 120

100 100

80 80

60 60

40 40 Effective Effective Rainfall(mm) Effective Rainfall(mm) 20 20 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Nov-19 Dec-19

RIVER TEST AT CHILBOLTON RIVER ITCHEN AT ALLBROOK GS AND HIGHBRIDGE Ranking used data from 09/01/1989 to 31/12/2017 Ranking used data from 01/10/1958 to 31/12/2017 16 14

14 12

12 10

10 8 8 6 6

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

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

RIVER TEST AT BROADLANDS LYMINGTON RIVER AT BROCKENHURST Ranking used data from 01/10/1957 to 31/12/2017 Ranking used data from 01/01/1997 to 31/12/2017 35 20

18 30 16

25 14

12 20 10 15 8

10 6

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

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

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

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West Hampshire – Page 2

CLANVILLE GATE GWL - CHALK PRESTON CANDOVER GWL - CHALK Ranking derived from data for the period Mar-1963 to Dec-2012 Ranking derived from data for the period Jan-1975 to Dec-2012

98 90 97 88 96 86 95 84 94 82 93 80 92 Level (mAOD) Level (mAOD) Level 78 91 76 90 74 89 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-19 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-19

WEST MEON GWL - CHALK LOPCOMBE CORNER GWL - CHALK Ranking derived from data for the period Sep-1986 to Dec-2012 Ranking derived from data for the period Apr-1963 to Dec-2012

94 95 92 93 90 91 88 89 86 87 84 85 82 83 Level (mAOD) Level (mAOD) Level 80 81 78 79 76 77 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-19 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-19

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

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East Hampshire and Isle of Wight

Monthly total rainfall (mm) Long term average rainfall (mm) East Hampshire Chalk - Rainfall Isle of Wight - Rainfall 180 160

160 140

140 120 120 100 100 80 80 60 60

Rainfall(mm) Rainfall(mm) 40 40

20 20

0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19

East Hampshire Chalk - Effective Rainfall Isle of Wight - Effective Rainfall 160 160

140 140

120 120

100 100

80 80

60 60

RIVER WALLINGTON AT NORTH FAREHAM RIVER MEON AT MISLINGFORD Ranking used data from 01/01/1992 to 31/12/2017 Ranking used data from 01/10/1958 to 31/12/2017 8 4.5

7 4.0

3.5 6

3.0 5 2.5 4 2.0 3 1.5

2 1.0 Daily Mean Flow (cumecs) Daily Mean Flow (cumecs) 1 0.5

0 0.0 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19

RIVER MEDINA AT BLACKWATER Ranking used data from 01/05/1989 to 31/12/2017 1.4

1.2

1.0

0.8

0.6

0.4

Daily Mean Flow (cumecs) 0.2

0.0 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19

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

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East Hampshire and Isle of Wight – Page 2

CATHERINGTON GWL - CHALK CARISBROOKE CASTLE GWL - CHALK Ranking derived from data for the period Jan-1969 to Dec-2012 Ranking derived from data for the period Aug-1977 to Dec-2012

32 52 31

47 30 29 42 28

37 27 Level (mAOD) Level (mAOD) Level 26 32 25

27 24 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-19 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-19

YOUNGSWOOD COPSE GWL - LGS Ranking derived from data for the period Feb-1978 to Dec-2012

19 Level (mAOD) Level 18

17 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-19

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

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West Sussex

Monthly total rainfall (mm) Long term average rainfall (mm) Arun - Rainfall West Sussex Chalk - Rainfall 160 180

140 160

140 120 120 100 100 80 80 60 60

Rainfall(mm) 40 Rainfall(mm) 40

20 20 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 0 0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19

Arun - Effective Rainfall West Sussex Chalk - Effective Rainfall 160 180

140 160

140 120 120 100 100 80 80 60 60 40 40 Effective Effective Rainfall(mm) Effective Rainfall(mm)

20 20 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Nov-19 Dec-19

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 20 45

18 40

16 35 14 30 12 25 10 20 8 15 6 10 4 Daily Mean Flow (cumecs) Daily Mean Flow (cumecs) 2 5

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

CHILGROVE HOUSE GWL - CHALK HARTING COMMON (DOWN) GWL - LGS Ranking derived from data for the period Feb-1836 to Dec-2012 Ranking derived from data for the period Jan-1984 to Dec-2012

75 100

70 100

65 99

60 99

55 98

50 98 Level (mAOD) Level (mAOD) Level 45 97

40 97

35 96 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-19 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-19

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

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East Sussex

Monthly total rainfall (mm) Long term average rainfall (mm) Pevensey Levels - Rainfall Ouse - Rainfall 180 180

160 160

140 140

120 120

100 100

80 80

60 60 Rainfall(mm) Rainfall(mm) 40 40

20 20

0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19

Pevensey Levels - Effective Rainfall Ouse - Effective Rainfall 180 160

160 140

140 120 120 100 100 80 80 60 60 40 40 Effective Effective Rainfall(mm) Effective Rainfall(mm)

20 20 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Jun-19 0 Jan-19 Feb-19 Mar-19 Apr-19 May-19 Nov-19 Dec-19

RIVER OUSE AT GOLDBRIDGE RIVER ADUR AT SAKEHAM Ranking used data from 01/03/1960 to 31/12/2017 Ranking used data from 01/05/1981 to 31/12/2017 60 40

35 50

40 25

30 20

15 20

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

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

RIVER CUCKMERE AT COWBEECH Ranking used data from 01/11/1967 to 31/12/2017 5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0 Daily Mean Flow (cumecs) 0.5

0.0 28-Feb-19 30-Apr-19 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19

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

East Sussex – Page 2

Monthly total rainfall (mm) Long term average rainfall (mm) BEEDING HILL GWL - CHALK HOUNDEAN BOTTOM GWL - CHALK Ranking derived from data for the period Sep-1979 to Dec-2012 Ranking derived from data for the period Jan-1977 to Dec-2012

75 24 73

71 19

69 14 67

65 9 Level (mAOD) Level (mAOD) Level 63 4 61

59 -1 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-19 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-19

CORNISH FARM WIGDENS GWL - CHALK LTA MIN 2015 2017 2018 2019 Ranking derived from data for the period Mar-1981 to Dec-2012 South East Water - Ardingly Reservoir - Ouse 23 100 22

21 80 20 19 60 18 17 40

Level (mAOD) Level 16 15 14 20 Percentage of live capacity live of Percentage 13 Mar-17 Jul-17 Nov-17 Mar-18 Jul-18 Nov-18 Mar-19 Jul-19 Nov-19 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

LTA MIN 2015 2017 2018 2019 South East Water - Arlington Reservoir - Cuckmere 100

20 Percentage of live capacity live of Percentage

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

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

Summary of rainfall, effective rainfall and soil moisture deficits

Rainfall and effective rainfall LTA LTA % Effective % Rainfall effective rainfall of rainfall of Area (mm) rainfall (mm) LTA (mm) LTA (mm) Test Chalk 144 88 161% 141 55 255% East Hampshire Chalk 153 93 162% 150 65 232% West Sussex Chalk 162 94 170% 159 72 222% East Sussex Chalk 148 88 167% 145 62 233% Isle of Wight 146 87 166% 142 60 237% Western Rother Greensand 167 98 168% 164 69 238% Hampshire Tertiaries 140 89 159% 137 64 214% Lymington 140 91 153% 137 67 203% Sussex Coast 130 77 165% 127 51 251% Arun 148 86 170% 145 65 223% Adur 147 85 171% 144 63 230% Ouse 146 86 167% 143 70 205% Cuckmere 135 85 159% 132 66 199% Pevensey Levels 131 81 159% 127 60 212% Solent and South Downs 146 88 166% 142 63 224%

Winter rainfall and effective rainfall Winter totals for the period 1st October to 31st December

LTA LTA % Effective % Rainfall effective rainfall of rainfall of Area (mm) rainfall (mm) LTA (mm) LTA (mm) Test Chalk 380 240 158% 292 103 283% East Hampshire Chalk 398 266 150% 323 132 244% West Sussex Chalk 457 284 161% 374 162 231% East Sussex Chalk 477 278 171% 370 145 255% Isle of Wight 418 265 158% 316 129 245% Western Rother Greensand 446 285 157% 379 148 257% Hampshire Tertiaries 376 252 149% 302 125 241% Lymington 395 263 150% 321 140 229% Sussex Coast 368 235 156% 264 104 255% Arun 400 253 158% 326 138 236% Adur 432 259 167% 341 139 246% Ouse 445 267 167% 361 155 233% Cuckmere 440 270 163% 350 146 240% Pevensey Levels 416 263 158% 313 133 235% Solent and South Downs 418 263 159% 331 136 244%

Soil Moisture Deficit

Area End of month SMD (mm) End of month SMD LTA (mm)

Test Chalk 0 6 East Hampshire Chalk 0 3 West Sussex Chalk 0 2 East Sussex Chalk 0 4 Isle of Wight 0 5 Western Rother Greensand 0 2 Hampshire Tertiaries 0 3 Lymington 0 1 Sussex Coast 0 4 Arun 0 1 Adur 0 2 Ouse 0 1 Cuckmere 0 1 Pevensey Levels 0 1 Solent and South Downs 0 3

Forward look- river flow and groundwater March 2020

a) 120% of LTA b) 100% of LTA rainfall rainfall

c) 80% of LTA d) 60% of LTA rainfall rainfall

Projected river flows at key indicator sites up until the end of March 2020. Projected groundwater levels at key indicator sites at the end of March 2020. Projections based on four scenarios: 120% (a), 100% (b), 80% (c) and 60% (d) of long term average

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).