Monthly water situation report - Kent and South London Area - Gov.uk
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Monthly water situation report
Kent and South London Area
Summary – June 2021
After a dry start, June turned out to be a second consecutive wet month with 183% of the Long
Term Average rainfall across the Kent and South London area as a whole, and totals ranging
from above normal to notably high. Soil moisture deficits increased in dry weather in the first
two weeks before decreasing back to below average by the end of the month. Monthly mean
flows ranged from above normal to notably high, and although groundwater levels continued
to recede, the heavy rain slowed or arrested the rate of recession later in the month at many
sites, with levels ending mostly above normal, but normal in the west of the area.
Rainfall
After a dry start, June turned out to be a second consecutive wet month with 183% of the Long Term
Average rainfall (LTA) across the Kent and South London area (KSL) as a whole. Totals ranged from
above normal to notably high, and were more than twice the LTA in the Sheppey and North West
Grain rainfall areas. The first half of the month was dry but for a front that brought widespread rain on
the 4th, the highest total then being 22mm at Faversham. The second half began with six consecutive
wet days, 16th-21st, with the heaviest rain on the 16th, when Parsonage Farm in the Upper Stour
catchment recorded 45mm. Some totals also exceeded 25mm on the 17th and 21st. After a drier
interlude, further widespread and often heavy rain fell on 27 -28th, the highest total then being 36mm at
Crossness by the Thames in south east London.
Soil Moisture Deficit/Recharge
Soil moisture deficits increased in the dry weather at the start of June, before d ecreasing to end the
month lower than the LTA everywhere. The rain in the second half of the month was heavy enough to
generate localised recharge, slowing or arresting the rate of groundwater level recession.
River Flows
Monthly mean river flows ranged from above normal to notably high. Except at groundwater-
dominated Crabble Mill on the River Dour, this reflects an average of relatively low flows in early June
and higher flows after the rain, as the daily mean flow charts show. Following the heaviest rain mid -
month, 10 fluvial flood alerts were issued, with a further one near the end of the month.
Groundwater Levels
Groundwater levels continued to recede as is usual in June, but at many sites the recession was
slowed later in the month following the heavy rain, and the most sensitive observation boreholes (OBH)
showed a small rise. Levels in the area's main aquifers ended the month still mostly above normal
after the wet winter, locally higher than this in north Kent and Thanet, but normal in the west of the
area, represented by Chipstead OBH.
Reservoir Storage
Reservoir levels dropped during the month as is usual, except for Weir Wood which stayed full. Bewl
levels fell only marginally, ending the month still in the normal range at 86% of capacity while Darwell
dropped to 68%, which is below normal. Both Bough Beech and Powdermill were normal at 83% and
82% respectively.
Author: Groundw ater & Hydrology Team Contact details: 03708 506 506
Al l da ta are provisional a nd may be subject to rev ision. The v iews expressed i n this document a re not necessarily those of the
Env i ronment Agency. Its officers, servants or a gents a ccept no l iability f or a ny l oss or da mage a rising from the i nterpretati on or
use of the i nformation, or reliance upon views contained herein.
© Environment A gency 2021
Rainfall Map 1
Total rainfall for hydrological areas across Kent and South London for the current month, classed relative to an
analysis of respective historic totals.
HadUK data based on the Met Office 1km gridded rainfall dataset derived from rain gauges (Source: Met Office ©
Crow n Copyright 2021). 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 w ith the permission of the controller of Her Majesty’s
Stationery Office © Crow n copyright. All rights reserved. Environment Agency, 100026380, 2021.
www.gov.uk/environment-agency © Environment A gency 2021
Rainfall Map 2
Total rainfall for hydrological areas across Kent and South London 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.
HadUK data based on the Met Office 1km gridded rainfall dataset derived from rain gauges (Source: Met Office ©
Crow n Copyright 2021). 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 w ith the permission of the controller of Her Majesty’s
Stationery Office © Crow n copyright. All rights reserved. Env ironment Agency, 100026380, 2021.
www.gov.uk/environment-agency © Environment A gency 2021River Flow, Groundwater and Reservoir Status Map
Groundw ater site status based on end of month level. River flow site status based on mean monthly flow .
Reservoir status based on end of month level, show ing percent full.
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 w ith the permission of the controller of Her
Majesty’s Stationery Office © Crow n copyright. All rights reserved. Environment Agency, 100026380, 2021.
Geological map reproduced w ith kind permission from UK Groundw ater Forum, BGS © NERC
www.gov.uk/environment-agency © Environment A gency 2021Tideway and South London (Rainfall and River Flows)
Monthly total rainfall (mm) Long term average rainfall (mm)
South London - Rainfall Upper Mole - Rainfall
180 200
160 180
160
140
140
120
120
Rainfall (mm)
Rainfall (mm)
100
100
80
80
60
60
40
40
20 20
0 0
Jul-20
Aug-20
Sep-20
Oct-20
Nov-20
Dec-20
Jan-21
Feb-21
Mar-21
Apr-21
May-21
Jun-21
Jul-20
Aug-20
Sep-20
Oct-20
Nov-20
Dec-20
Jan-21
Feb-21
Mar-21
Apr-21
May-21
Jun-21
South London - Effective Rainfall Upper Mole - Effective Rainfall
120 140
120
100
Effective Rainfall (mm)
Effective Rainfall (mm) 100
80
80
60
60
40
40
20
20
0 0
Jul-20
Aug-20
Sep-20
Oct-20
Nov-20
Dec-20
Jan-21
Feb-21
Mar-21
Apr-21
May-21
Jun-21
Jul-20
Aug-20
Sep-20
Oct-20
Nov-20
Dec-20
Jan-21
Feb-21
Mar-21
Apr-21
May-21
Jun-21
RIVER MOLE AT DORKING GS RIVER WANDLE AT CONNOLLY'S MILL GS
Ranking used data from 01/11/1971 to 31/12/2017 Ranking derived from data for the period 01/01/1980 to 31/12/2017
35 8
30 7
Daily Mean Flow (cumecs)
Daily Mean Flow (cumecs)
6
25
5
20
4
15
3
10
2
5 1
0 0
30-Aug-20 30-Oct-20 30-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 30-Aug-20 30-Oct-20 30-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21
RIVER RAVENSBOURNE AT CATFORD GS RIVER DARENT AT HAWLEY
Ranking used data from 01/12/1977 to 31/12/2017 Ranking derived from data for the period 01/12/1963 to 31/12/2017
3.5 4.5
4.0
3.0
3.5
Daily Mean Flow (cumecs)
Daily Mean Flow (cumecs)
2.5
3.0
2.0 2.5
1.5 2.0
1.5
1.0
1.0
0.5
0.5
0.0 0.0
30-Aug-20 30-Oct-20 30-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 30-Aug-20 30-Oct-20 30-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21
Exceptionally high Notably high Above normal Normal
Below normal Notably low Exceptionally low ─── Latest data
www.gov.uk/environment-agency © Environment A gency 2021Tideway and South London (Groundwater Levels)
NORTH DOWNS - CHIPSTEAD - CHALK NORTH DOWNS - SWEEPS LANE - CHALK
Ranking derived from data for the period Oct-1942 to Dec-2017 Ranking derived from data for the period Jan-1984 to Dec-2017
104 46
102
100
98
Level (mAOD)
Level (mAOD)
45
96
94
92
44
90
88
86
84 43
Sep-19 Dec-19 Mar-20 Jun-20 Sep-20 Dec-20 Mar-21 Jun-21 Sep-19 Dec-19 Mar-20 Jun-20 Sep-20 Dec-20 Mar-21 Jun-21
RIVERHEAD - LOWER GREENSAND
Ranking derived from data for the period Jan-1965 to Dec-2017
80
79
Level (mAOD)
78
77
76
75
74
Sep-19 Dec-19 Mar-20 Jun-20 Sep-20 Dec-20 Mar-21 Jun-21
Exceptionally high Notably high Above normal Normal
Below normal Notably low Exceptionally low ─── Latest data
www.gov.uk/environment-agency © Environment A gency 2021East Kent (Rainfall and River flows)
Monthly total rainfall (mm) Long term rainfall (mm)
Stour - Rainfall Dover Chalk - Rainfall
180 250
160
200
140
120
150
Rainfall (mm)
Rainfall (mm)
100
80
100
60
40
50
20
0 0
Jul-20
Aug-20
Sep-20
Oct-20
Nov-20
Dec-20
Jan-21
Feb-21
Mar-21
Apr-21
May-21
Jun-21
Jul-20
Aug-20
Sep-20
Oct-20
Nov-20
Dec-20
Jan-21
Feb-21
Mar-21
Apr-21
May-21
Jun-21
Stour - Effective Rainfall Dover Chalk - Effective Rainfall
160 180
140 160
140
120
Effective Rainfall (mm)
Effective Rainfall (mm)
120
100
100
80
80
60
60
40
40
20 20
0 0
Jul-20
Aug-20
Sep-20
Oct-20
Nov-20
Dec-20
Jan-21
Feb-21
Mar-21
Apr-21
May-21
Jun-21
Jul-20
Aug-20
Sep-20
Oct-20
Nov-20
Dec-20
Jan-21
Feb-21
Mar-21
Apr-21
May-21
Jun-21
GREAT STOUR AT HORTON EAST STOUR AT SOUTH WILLESBOROUGH GS
Ranking derived from data for the period 01/10/1964 to 31/12/2017 Ranking derived from data for the period 01/01/1976 to 31/12/2017
18 10
16 9
8
14
Daily Mean Flow (cumecs)
Daily Mean Flow (cumecs)
7
12
6
10
5
8
4
6
3
4
2
2 1
0 0
30-Aug-20 30-Oct-20 30-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 30-Aug-20 30-Oct-20 30-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21
RIVER DOUR AT CRABBLE MILL
Ranking derived from data for the period 06/01/1976 to 31/12/2017
1.6
1.4
Daily Mean Flow (cumecs)
1.2
1.0
0.8
0.6
0.4
0.2
0.0
30-Aug-20 30-Oct-20 30-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21
Exceptionally high Notably high Above normal Normal
Below normal Notably low Exceptionally low ─── Latest data
www.gov.uk/environment-agency © Environment A gency 2021East Kent (Groundwater Levels)
NORTH DOWNS - WOLVERTON - CHALK NORTH DOWNS - LITTLE BUCKET - CHALK
Ranking derived from data for the period Oct-1970 to Dec-2017 Ranking derived from data for the period Jan-1971 to Dec-2017
46 90
44
85
42
80
Level (mAOD)
Level (mAOD)
40
38 75
36 70
34
65
32
60
30
28 55
Sep-19 Dec-19 Mar-20 Jun-20 Sep-20 Dec-20 Mar-21 Jun-21 Sep-19 Dec-19 Mar-20 Jun-20 Sep-20 Dec-20 Mar-21 Jun-21
THANET CHALK - ALLAND GRANGE - CHALK NORTH DOWNS - RIDDLES LANE - CHALK
Ranking derived from data for the period Nov-1969 to Dec-2017 Ranking derived from data for the period Apr-1982 to Dec-2017
8 28
26
7
24
Level (mAOD)
Level (mAOD)
6 22
20
5
18
4 16
14
3
12
2 10
Sep-19 Dec-19 Mar-20 Jun-20 Sep-20 Dec-20 Mar-21 Jun-21 Sep-19 Dec-19 Mar-20 Jun-20 Sep-20 Dec-20 Mar-21 Jun-21
Exceptionally high Notably high Above normal Normal
Below normal Notably low Exceptionally low ─── Latest data
www.gov.uk/environment-agency © Environment A gency 2021Medway and Rother (Rainfall and River Flow)
Monthly total rainfall (mm) Long term average rainfall (mm)
River Medway - Rainfall Eastern Rother - Rainfall
200 200
180 180
160 160
140 140
120 120
Rainfall (mm)
Rainfall (mm)
100 100
80 80
60 60
40 40
20 20
0 0
Jul-20
Aug-20
Sep-20
Oct-20
Nov-20
Dec-20
Jan-21
Feb-21
Mar-21
Apr-21
May-21
Jun-21
Jul-20
Aug-20
Sep-20
Oct-20
Nov-20
Dec-20
Jan-21
Feb-21
Mar-21
Apr-21
May-21
Jun-21
River Medway - Effective Rainfall Eastern Rother - Effective Rainfall
140 160
120 140
120
Effective Rainfall (mm)
100 Effective Rainfall (mm)
100
80
80
60
60
40
40
20 20
0 0
Jul-20
Aug-20
Sep-20
Oct-20
Nov-20
Dec-20
Jan-21
Feb-21
Mar-21
Apr-21
May-21
Jun-21
Jul-20
Aug-20
Sep-20
Oct-20
Nov-20
Dec-20
Jan-21
Feb-21
Mar-21
Apr-21
May-21
Jun-21
RIVER MEDWAY AT TESTON & EAST FARLEIGH COMBINED RIVER TEISE AT STONEBRIDGE
Ranking derived from data for the period 01/10/1956 to 31/12/2017 Ranking derived from data for the period 01/10/1961 to 31/12/2017
100 12
90
10
80
Daily Mean Flow (cumecs)
Daily Mean Flow (cumecs)
70
8
60
50 6
40
4
30
20
2
10
0 0
30-Aug-20 30-Oct-20 30-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 30-Aug-20 30-Oct-20 30-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21
RIVER EDEN AT VEXOUR / PENSHURST GS RIVER ROTHER AT UDIAM GS
Ranking derived from data for the period 01/11/2003 to 31/12/2017 Ranking derived from data for the period 01/10/1962 to 31/12/2017
18 25
16
20
14
Daily Mean Flow (cumecs)
Daily Mean Flow (cumecs)
12
15
10
8
10
6
4
5
2
0 0
30-Aug-20 30-Oct-20 30-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21 30-Aug-20 30-Oct-20 30-Dec-20 28-Feb-21 30-Apr-21 30-Jun-21
Exceptionally high Notably high Above normal Normal
Below normal Notably low Exceptionally low ─── Latest data
www.gov.uk/environment-agency © Environment A gency 2021Medway and Rother (Reservoir Storage)
LTA MIN 2020 2021 LTA MIN 2020 2021
SES Water - Bough Beech Reservoir - Medway
Southern Water - Bewl Reservoir - Teise (Medway)
100 100
90
Percentage of live capacity
Percentage of live capacity
80 80
70
60 60
50
40 40
30
20 20
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
LTA MIN 2020 2021 LTA MIN 2020 2021
Southern Water - Darwell Reservoir - Rother (Eastern) Southern Water - Powdermill Reservoir - Brede
100
100
Percentage of live capacity
Percentage of live capacity
80 80
60 60
40 40
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
LTA MIN 2020 2021
Southern Water - Weir Wood Reservoir - Medway
100
Percentage of live capacity
80
60
40
20
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
www.gov.uk/environment-agency © Environment A gency 2021Summary of June-2021 Rainfall, Effective Rainfall and Soil Moisture Deficit calculated up to
the 30th of the month
Summer period:
Effective Rainfall 01/04/2021 to
Rainfall (mm) (mm) SMD (mm) 30/06/2021
30 30 End Effective Rainfall
day June day June June Rainfall (mm) (mm)
Day %
Number Name Total LTA % LTA total LTA % LTA 30 LTA Total LTA % LTA Total LTA LTA
North Downs - South
6230TH 90 57 157% 9 6 147% 65 74 180 174 103% 16 33 48%
London (W)
6505TH Upper Mole 83 55 149% 0 3 0% 59 70 183 169 108% 0 28 0%
6508TH South London 84 51 165% 0 1 0% 71 80 157 150 105% 0 14 0%
6706So Darent 100 52 191% 10 4 242% 79 83 174 156 111% 14 21 68%
6707So North Kent Chalk 101 54 189% 10 7 140% 63 67 178 157 114% 15 31 48%
6708So Stour 91 52 175% 9 5 172% 63 68 185 150 124% 16 25 62%
6709So Dover Chalk 91 55 164% 8 5 163% 67 69 190 161 118% 16 32 50%
6710So Thanet Chalk 95 49 193% 10 4 246% 71 92 174 131 133% 14 14 101%
6809So Medway 100 53 189% 0 3 0% 51 70 189 159 119% 0 22 0%
6810So Eastern Rother 102 53 193% 0 3 0% 41 61 202 155 130% 0 25 0%
6811So Romney Marsh 94 49 194% 0 1 0% 50 65 183 142 129% 0 18 0%
6812So North West Grain 101 46 220% 0 0 0% 72 89 161 133 121% 0 6 0%
6813So Sheppey 102 46 223% 0 0 0% 64 83 175 131 133% 0 9 0%
Kent & South London Average 95 52 183% 4 3 130% 63 75 179 151 118% 7 21 33%
Estimate of areal rainfall, effective rainfall (i.e. percolation/runoff) and soil moisture deficit. Provisional data based on Environment Agency 1km gridded rainfall dataset derived
from Environment Agency intensity rain gauges. There may be significant variation w ithin each area w hich must be considered w hen interpreting these data. When additional
meteorological data is available estimates are revised, this w ill affect period totals.
© Environment A gency 2021Glossary
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 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
LIT 9036
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