Water Situation Report
Monthly water situation report England Summary – September 2017 September rainfall was well above the monthly long term average at 133%. Monthly rainfall totals were normal or higher for the time of year across all hydrological areas. Soil moisture deficit decreased during September across much of England and at the end of the month, soils were wetter than average across most areas. Monthly mean river flows increased compared to August at just over half of indicator sites and were classed as normal or higher for the time of year at all but 5 sites. Groundwater levels continued to recede at all but 6 indicator sites during September but end of month levels were normal or higher for the time of year at just over half of the indicator sites. Reservoir stocks decreased at nearly two-thirds of reported reservoirs or reservoir groups, but stocks remain normal or higher for the time of year at just over three-quarters of sites. Overall reservoir storage for England remained unchanged at the end of September at 79% of total capacity.
Rainfall September monthly rainfall totals were highest across parts of north-west and south-west England at 150 to 230mm and lowest across parts of Kent, Essex, Suffolk and south London at 40 to 50mm. Rainfall totals were above the September long term average (LTA) across more than four-fifths of hydrological areas, with parts of Devon, Cornwall and North Yorkshire receiving approximately 175 to 200% of the LTA. Hydrological areas receiving below the LTA were concentrated in south-east England with the Isle of Thanet in Kent receiving 70% of the LTA (Figure 1.1). Rainfall totals for September were classed as normal to notably high for the time of year across all of the hydrological areas. Cumulative rainfall totals for the past 3 and 6 months show a similar picture across England. However, the rainfall deficit is still evident in the 12 month cumulative rainfall totals, with much of south-west, southeast and central England being below normal or notably low for the time of year (Figure 1.2). At a regional scale, September rainfall totals were above average across all regions, ranging from 110% of the LTA in south-east England to 147% in both north-east and north-west England. September rainfall was classed as normal for the time of year across east and south-east England, notably high in north-west England and above normal elsewhere. The monthly rainfall total for England was 133% of the 1961-90 LTA for September (136% of the 1981-2010 LTA) (Figure 1.3).
Soil moisture deficit In response to the above average September rainfall, soil moisture deficits (SMDs) generally decreased across England during September. With the exception of parts of Essex and Suffolk, soils were wetter at the end of September than at the end of August across the whole of England, with SMDs ranging from approximately 1mm in parts of north-west and south-west England to just over 140mm across parts of Norfolk and Cambridgeshire. At the end of the month, soils were wetter than the September LTA across much of England, particularly along the south coast and across parts of south-west, central and north-east England. Soils were drier than average across much of east England and the area around the lower River Severn and Severn Estuary (Figure 2.1). At a regional scale, soils were wetter at the end of September compared to the end of August across all regions, with end of month SMDs ranging from 11mm in north-west England to 87mm in east England. SMDs were approximately average for the time of year in east and central England but smaller than average (wetter soils) elsewhere (Figure 2.2).
River flows September monthly mean river flows increased compared to August at just over half of the indicator sites across England. Flows were classed as normal or higher for the time of year at all but 4 indicator sites; flows in the rivers Kennet, Great Stour and Eastern Rother in south-east England and the River Avon in south-west England were
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.
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© Environment Agency 2017
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below normal for the time of year. Flows at all indicator sites in north-west England were above normal or notably high the time of year (Figure 3.1). At the regional index sites, monthly mean river flows were below normal for the time of year on the Great Stour in south-east England but normal or above normal elsewhere (Figure 3.2).
Groundwater levels Groundwater levels continued to recede during September at the majority of sites; increases were recorded at 4 sites in sandstone aquifers in central and north-west England and 2 chalk aquifer sites, Wetwang in the Hull and East Riding chalk and Woodyates in the Upper Dorset Stour chalk. End of month groundwater levels were below normal or lower for the time of year at just under half of the indicator sites, with Ashley Green (Chilterns East chalk aquifer) remaining exceptionally low for the fourth consecutive month. End of month groundwater levels at the major aquifer index sites ranged from notably low for the time of year at Little Bucket (East Kent Stour chalk aquifer), Stonor Park (South West Chilterns chalk aquifer) and Redlands (Cam and Ely Ouse chalk aquifer) to above normal for the time of year at Dalton Holme (Hull and East Riding chalk aquifer) (Figures 4.1 and 4.2).
Reservoir storage Reservoir stocks decreased at nearly two-thirds of the reported reservoirs or reservoir groups during September. The largest decreases (9%) occurred in the Lower Lee and Lower Thames reservoir groups. In contrast, stocks increased in the Elan Valley and Teesdale reservoir groups by 10 and 13% respectively. End of month stocks were classed as normal or higher for the time of year at just over three-quarters of all reported reservoirs and reservoir groups. The remaining sites were classed as below normal for the time of year, whilst Bewl Reservoir remained classed as notably low for the sixth consecutive month (Figure 5.1). Compared with the end of August, regional reservoir stocks increased by between 1 and 4% in north-east, northwest and central England, decreased by 8% in south-east England and decreased only slightly elsewhere. End of September stocks ranged from 67% of total capacity in south-west England to 86% in east England. Overall storage for England remained unchanged at 79% of total capacity (Figure 5.2).
Forward look October is likely to see a mix of settled conditions and wet and windy weather, with the heaviest rainfall in the north and west of the country. For the 3-month period October to December above-average rainfall is more considered probable than below-average rainfall1. Projections for river flows at key sites2 Just over half of the modelled sites have a greater than expected chance of cumulative river flows being normal or higher the end of March 2018. By the end of September 2018, two-fifths of the modelled sites have a greater than expected chance of being normal or higher for the time of year. For scenario based projections of cumulative river flows at key sites by March 2018 see Figure 6.1 For scenario based projections of cumulative river flows at key sites by September 2018 see Figure 6.2 For probabilistic ensemble projections of cumulative river flows at key sites by March 2018 see Figure 6.3 For probabilistic ensemble projections of cumulative river flows at key sites by September 2018 see Figure 6.4 Projections for groundwater levels in key aquifers2 Just over half of the modelled sites have a greater than expected chance of groundwater levels being normal or higher for the time of year at the end of March 2018. By September 2018, nearly three-fifths of the modelled sites have a greater than expected chance of groundwater levels being normal or higher for the time of year. For scenario based projections of groundwater levels in key aquifers in March 2018 see Figure 6.5 For scenario based projections of groundwater levels in key aquifers in September 2018 see Figure 6.6 For probabilistic ensemble projections of groundwater levels in key aquifers in March 2018 see Figure 6.7 For probabilistic ensemble projections of groundwater levels in key aquifers in September 2018 see Figure 6.8 Authors:
1 2
National Water Resources Hydrology Team
Source: Met Office Information produced by the Water Situation Forward Look group led by Environment Agency in partnership with the Centre for Ecology and Hydrology, British Geological Survey, Met Office (www.hydoutuk.net).
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© Environment Agency 2017
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Rainfall
October 2016
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May 2017
June 2017
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September 2017
Figure 1.1: Monthly rainfall across England and Wales for the past 12 months. UKPP radar data (Source: Met Office © Crown Copyright, 2017). Note: Radar beam blockages in some regions may give anomalous totals in some areas. Crown copyright. All rights reserved. Environment Agency, 100026380, 2017.
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© Environment Agency 2017
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Figure 1.2: Total rainfall for hydrological areas across England for the current month (up to 30 September), 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, 2017). 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, 2017.
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© Environment Agency 2017
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Rainfall charts
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© Environment Agency 2017
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Jan-17 Dec-16 Nov-16 Oct-16 Sep-16
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Figure 1.3: Monthly rainfall totals for the past 24 months as a percentage of the 1961 – 1990 long term average for each region and for England. NCIC (National Climate Information Centre) data. (Source: Met Office © Crown Copyright, 2017).
Soil moisture deficit End of August 20171
End of September 20172
Figure 2.1: Soil moisture deficits for weeks ending 29 August 2017 1 (left panel) and 3 October 2017 2 (right panel). Top row shows actual soil moisture deficits (mm) and bottom row shows the difference (mm) of the actual from the 1961-90 long term average soil moisture deficits. MORECS data for real land use (Source: Met Office © Crown Copyright, 2017). Crown copyright. All rights reserved. Environment Agency, 100026380, 2017
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© Environment Agency 2017
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Soil moisture deficit charts Central England 0
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Figure 2.2: Latest soil moisture deficits for all geographic regions compared to maximum, minimum and 1961-90 long term average. Weekly MORECS data for real land use. (Source: Met Office © Crown Copyright, 2017).
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River flows
^
“Naturalised” flows are provided for the River Thames at Kingston and the River Lee at Feildes Weir
*
Data for the River Coln at Bibury is currently under investigation Underlined sites are regional index sites and are shown on the hydrographs in Figure 3.2
Figure 3.1: Monthly mean river flow for indicator sites for August 2017 and September 2017, expressed as a percentage of the respective long term average and classed relative to an analysis of historic August and September monthly means (Source: Environment Agency). Crown copyright. All rights reserved. Environment Agency, 100026380, 2017.
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© Environment Agency 2017
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River flow charts Exceptionally high Below normal ─ ─ ─ Monthly maximum
Notably high Notably low ─── Latest data
Above normal Exceptionally low ─ ─ ─ Monthly minimum
Offord, BEDFORD OUSE Ranking derived from data for the period Jan-1970 to Dec-2012
Normal
Marston-on-Dove, DOVE Ranking derived from data for the period Jul-1965 to Dec-2012
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Caton, LUNE Ranking derived from data for the period Jan-1959 to Dec-2012 140 120
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Figure 3.2: Index river flow sites for each geographic region. Monthly mean flow compared to an analysis of historic monthly mean flows, long term maximum and minimum flows. (Source: Environment Agency).
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© Environment Agency 2017
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Groundwater levels
^ The level at Priors Heyes remains high compared to historic levels because the aquifer is recovering from the effects of historic abstraction ^^ Sites are manually dipped at different times during the month. They may not be fully representative of levels at the month end Underlined sites are major aquifer index sites and are shown in the groundwater level charts in Figure 4.2
Figure 4.1: Groundwater levels for indicator sites at the end of August 2017 and September 2017, classed relative to an analysis of respective historic August and September levels (Source: Environment Agency). Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC. Crown copyright. All rights reserved. Environment Agency, 100026380, 2017.
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© Environment Agency 2017
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Groundwater level charts Exceptionally high Below normal ─ ─ ─ Monthly maximum
Notably high Notably low ─── Latest data
Above normal Exceptionally low ─ ─ ─ Monthly minimum
Normal
Redlands Hall (Chalk)
Heathlanes (Sandstone)
Ranking derived from data for the period Aug-1963 to Dec-2012
Ranking derived from data for the period Jul-1971 to Dec-2012
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Level (mAOD)
Level (mAOD)
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Dalton Holme (Chalk)
Skirwith (Sandstone)
Ranking derived from data for the period Jan-1889 to Dec-2012
Ranking derived from data for the period Oct-1978 to Dec-2012
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Little Bucket (Chalk) Ranking derived from data for the period Jan-1971 to Dec-2012
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Ranking derived from data for the period Feb-1836 to Dec-2012 77
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Jackaments Bottom (Jurassic Limestone)
Stonor Park (Chalk)
Ranking derived from data for the period Jan-1974 to Dec-2012
Ranking derived from data for the period May-1961 to Dec-2012
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Figure 4.2: Index groundwater level sites for major aquifers. End of month groundwater levels months compared to an analysis of historic end of month levels and long term maximum and minimum levels. (Source: Environment Agency, 2017).
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Reservoir storage
1. Engineering work at Abberton Reservoir in east England to increase capacity has been completed 2. Vyrnwy, Clywedog and Elan Valley reservoirs are located in Wales but provide a water resource to central and north-west England 3. Current levels at Kielder will be deliberately lower than historical levels during a trial of a new flood alleviation control curve
Figure 5.1: Reservoir stocks at key individual and groups of reservoirs at the end of August and September 2017 as a percentage of total capacity and classed relative to an analysis of historic August and September values respectively (Source: Water Companies). Note: Classes shown may not necessarily relate to control curves or triggers for drought actions. As well as for public water supply, some reservoirs are drawn down to provide flood storage, river compensation flows or for reservoir safety inspections. In some cases current reservoir operating rules may differ from historic ones. Crown copyright. All rights reserved. Environment Agency, 100026380, 2017.
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© Environment Agency 2017
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East England
Central England
Based on storage in Abberton, Grafham, Hanningfield, Rutland reservoirs
Based on storage in Clywedog, Carsington and Ogston, Derwent Valley, Dove (Foremark & Staunton), Draycote, Elan Valley Group reservoirs
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Based on storage in Ardingly, Bewl, Bough Beech, Farmoor, Lower Lee Group, Lower Thames Group reservoirs
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────
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Figure 5.2: Regional reservoir stocks. End of month reservoir stocks compared to long term maximum, minimum and average stocks (Source: Water Companies). Note: Historic records of individual reservoirs/reservoir groups making up the regional values vary in length.
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Forward look – river flow Rainfall greater than 120% LTA during Oct to Mar has occurred in 16% to 27% of years¹ in the historic record (since 1910)
(a)
Rainfall greater than 100% LTA during Oct to Mar has occurred in 53% to 58% of years¹ in the historic record (since 1910)
(b)
Rainfall less than 60% LTA during Oct to Mar has occurred in less than 2% of years¹ in the historic record (since 1910)
Rainfall less than 80% LTA during Oct to Mar has occurred in 9% to 15% of years¹ in the historic record (since 1910)
(c)
(d)
Figure 6.1: Projected river flows at key indicator sites up until the end of March 2018. Projections based on four scenarios: 120% (a), 100% (b), 80% (c) and 60% (d) of long term average rainfall between October 2017 and March 2018 (Source: Centre for Ecology and Hydrology, Environment Agency). 1
This range of probabilities is a regional analysis Projections for these sites are produced by CEH 3 Projections for these sites are produced by the Environment Agency ^ “Naturalised” flows are projected for these sites 2
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© Environment Agency 2017
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Rainfall greater than 120% LTA during Oct to Sep has occurred in 9% to 18% of years¹ in the historic record (since 1910)
Rainfall greater than 100% LTA during Oct to Sep has occurred in 58% to 64% of years¹ in the historic record (since 1910)
(b)
(a)
Rainfall less than 80% LTA during Oct to Sep has occurred in 2% to 8% of years¹ in the historic record (since 1910)
(c)
Rainfall less than 60% LTA during Oct to Sep has occurred in less than 1% of years¹ in the historic record (since 1910)
(d)
Figure 6.2: Projected river flows at key indicator sites up until the end of September 2018. Projections based on four scenarios: 120% (a), 100% (b), 80% (c) and 60% (d) of long term average rainfall between October 2017 and September 2018 (Source: Centre for Ecology and Hydrology, Environment Agency). 1
This range of probabilities is a regional analysis Projections for these sites are produced by CEH Projections for these sites are produced by the Environment Agency ^ “Naturalised” flows are projected for these sites 2 3
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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.
Figure 6.3: Probabilistic ensemble projections of river flows at key indicator sites up until the end of March 2018. 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). 1
Projections for these sites are produced by the Environment Agency Projections for these sites are produced by CEH ^“Naturalised” flows are projected for these sites 2
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© Environment Agency 2017
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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.
Figure 6.4: Probabilistic ensemble projections of river flows at key indicator sites up until the end of September 2018. 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). 1
Projections for these sites are produced by the Environment Agency Projections for these sites are produced by CEH ^“Naturalised” flows are projected for these sites 2
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© Environment Agency 2017
17
Forward look - groundwater Rainfall greater than 120% LTA during Oct to Mar has occurred in 16% to 27% of years¹ in the historic record (since 1910) )
Rainfall greater than 100% LTA during Oct to Mar has occurred in 53% to 58% of years¹ in the historic record (since 1910)
(b)
(a)
Rainfall less than 80% LTA during Oct to Mar has occurred in 9% to 15% of years¹ in the historic record (since 1910)
(c)
Rainfall less than 60% LTA during Oct to Mar has occurred in less than 2% of years¹ in the historic record (since 1910)
(d)
Figure 6.5: Projected groundwater levels at key indicator sites at the end of March 2018. Projections based on four scenarios: 120% (a), 100% (b), 80% (c) and 60% (d) of long term average rainfall between October 2017 and March 2018 (Source: Environment Agency). Geological map reproduced with kind permission from UK Groundwater Forum BGS © NERC. Crown copyright all rights reserved. Environment Agency 100026380, 2017. * Projections for these sites are produced by BGS 1 This range of probabilities is a regional analysis
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© Environment Agency 2017
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Rainfall greater than 120% LTA during Oct to Sep has occurred in 9% to 18% of years¹ in the historic record (since 1910)
Rainfall greater than 100% LTA during Oct to Sep has occurred in 58% to 64% of years¹ in the historic record (since 1910)
(b)
(a)
Rainfall less than 80% LTA during Oct to Sep has occurred in 2% to 8% of years¹ in the historic record (since 1910)
(c)
Rainfall less than 60% LTA during Oct to Sep has occurred in less than 1% of years¹ in the historic record (since 1910)
(d)
Figure 6.6: Projected groundwater levels at key indicator sites at the end of September 2018. Projections based on four scenarios: 120% (a), 100% (b), 80% (c) and 60% (d) of long term average rainfall between October 2017 and September 2018 (Source: Environment Agency). Geological map reproduced with kind permission from UK Groundwater Forum BGS © NERC Crown copyright. All rights reserved. Environment Agency 100026380 2017. * Projections for these sites are produced by BGS 1 This range of probabilities is a regional analysis www.gov.uk/environment-agency
© Environment Agency 2017
19
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.
Figure 6.7: Probabilistic ensemble projections of groundwater levels at key indicator sites at the end of March 2018. 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. * Projections for these sites are produced by BGS
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© Environment Agency 2017
20
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.
Figure 6.8: Probabilistic ensemble projections of groundwater levels at key indicator sites at the end of September 2018. 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. * Projections for these sites are produced by BGS www.gov.uk/environment-agency
© Environment Agency 2017
21
Figure 7.1: Geographic regions Crown copyright. All rights reserved. Environment Agency, 100026380, 2017.
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© Environment Agency 2017
22
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. For rainfall and soil moisture deficit, the period refers to 1961-1990, unless otherwise stated. For other parameters, the period may vary according to data availability
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
www.gov.uk/environment-agency
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
Rainfall September monthly rainfall totals were highest across parts of north-west and south-west England at 150 to 230mm and lowest across parts of Kent, Essex, Suffolk and south London at 40 to 50mm. Rainfall totals were above the September long term average (LTA) across more than four-fifths of hydrological areas, with parts of Devon, Cornwall and North Yorkshire receiving approximately 175 to 200% of the LTA. Hydrological areas receiving below the LTA were concentrated in south-east England with the Isle of Thanet in Kent receiving 70% of the LTA (Figure 1.1). Rainfall totals for September were classed as normal to notably high for the time of year across all of the hydrological areas. Cumulative rainfall totals for the past 3 and 6 months show a similar picture across England. However, the rainfall deficit is still evident in the 12 month cumulative rainfall totals, with much of south-west, southeast and central England being below normal or notably low for the time of year (Figure 1.2). At a regional scale, September rainfall totals were above average across all regions, ranging from 110% of the LTA in south-east England to 147% in both north-east and north-west England. September rainfall was classed as normal for the time of year across east and south-east England, notably high in north-west England and above normal elsewhere. The monthly rainfall total for England was 133% of the 1961-90 LTA for September (136% of the 1981-2010 LTA) (Figure 1.3).
Soil moisture deficit In response to the above average September rainfall, soil moisture deficits (SMDs) generally decreased across England during September. With the exception of parts of Essex and Suffolk, soils were wetter at the end of September than at the end of August across the whole of England, with SMDs ranging from approximately 1mm in parts of north-west and south-west England to just over 140mm across parts of Norfolk and Cambridgeshire. At the end of the month, soils were wetter than the September LTA across much of England, particularly along the south coast and across parts of south-west, central and north-east England. Soils were drier than average across much of east England and the area around the lower River Severn and Severn Estuary (Figure 2.1). At a regional scale, soils were wetter at the end of September compared to the end of August across all regions, with end of month SMDs ranging from 11mm in north-west England to 87mm in east England. SMDs were approximately average for the time of year in east and central England but smaller than average (wetter soils) elsewhere (Figure 2.2).
River flows September monthly mean river flows increased compared to August at just over half of the indicator sites across England. Flows were classed as normal or higher for the time of year at all but 4 indicator sites; flows in the rivers Kennet, Great Stour and Eastern Rother in south-east England and the River Avon in south-west England were
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.
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© Environment Agency 2017
1
below normal for the time of year. Flows at all indicator sites in north-west England were above normal or notably high the time of year (Figure 3.1). At the regional index sites, monthly mean river flows were below normal for the time of year on the Great Stour in south-east England but normal or above normal elsewhere (Figure 3.2).
Groundwater levels Groundwater levels continued to recede during September at the majority of sites; increases were recorded at 4 sites in sandstone aquifers in central and north-west England and 2 chalk aquifer sites, Wetwang in the Hull and East Riding chalk and Woodyates in the Upper Dorset Stour chalk. End of month groundwater levels were below normal or lower for the time of year at just under half of the indicator sites, with Ashley Green (Chilterns East chalk aquifer) remaining exceptionally low for the fourth consecutive month. End of month groundwater levels at the major aquifer index sites ranged from notably low for the time of year at Little Bucket (East Kent Stour chalk aquifer), Stonor Park (South West Chilterns chalk aquifer) and Redlands (Cam and Ely Ouse chalk aquifer) to above normal for the time of year at Dalton Holme (Hull and East Riding chalk aquifer) (Figures 4.1 and 4.2).
Reservoir storage Reservoir stocks decreased at nearly two-thirds of the reported reservoirs or reservoir groups during September. The largest decreases (9%) occurred in the Lower Lee and Lower Thames reservoir groups. In contrast, stocks increased in the Elan Valley and Teesdale reservoir groups by 10 and 13% respectively. End of month stocks were classed as normal or higher for the time of year at just over three-quarters of all reported reservoirs and reservoir groups. The remaining sites were classed as below normal for the time of year, whilst Bewl Reservoir remained classed as notably low for the sixth consecutive month (Figure 5.1). Compared with the end of August, regional reservoir stocks increased by between 1 and 4% in north-east, northwest and central England, decreased by 8% in south-east England and decreased only slightly elsewhere. End of September stocks ranged from 67% of total capacity in south-west England to 86% in east England. Overall storage for England remained unchanged at 79% of total capacity (Figure 5.2).
Forward look October is likely to see a mix of settled conditions and wet and windy weather, with the heaviest rainfall in the north and west of the country. For the 3-month period October to December above-average rainfall is more considered probable than below-average rainfall1. Projections for river flows at key sites2 Just over half of the modelled sites have a greater than expected chance of cumulative river flows being normal or higher the end of March 2018. By the end of September 2018, two-fifths of the modelled sites have a greater than expected chance of being normal or higher for the time of year. For scenario based projections of cumulative river flows at key sites by March 2018 see Figure 6.1 For scenario based projections of cumulative river flows at key sites by September 2018 see Figure 6.2 For probabilistic ensemble projections of cumulative river flows at key sites by March 2018 see Figure 6.3 For probabilistic ensemble projections of cumulative river flows at key sites by September 2018 see Figure 6.4 Projections for groundwater levels in key aquifers2 Just over half of the modelled sites have a greater than expected chance of groundwater levels being normal or higher for the time of year at the end of March 2018. By September 2018, nearly three-fifths of the modelled sites have a greater than expected chance of groundwater levels being normal or higher for the time of year. For scenario based projections of groundwater levels in key aquifers in March 2018 see Figure 6.5 For scenario based projections of groundwater levels in key aquifers in September 2018 see Figure 6.6 For probabilistic ensemble projections of groundwater levels in key aquifers in March 2018 see Figure 6.7 For probabilistic ensemble projections of groundwater levels in key aquifers in September 2018 see Figure 6.8 Authors:
1 2
National Water Resources Hydrology Team
Source: Met Office Information produced by the Water Situation Forward Look group led by Environment Agency in partnership with the Centre for Ecology and Hydrology, British Geological Survey, Met Office (www.hydoutuk.net).
www.gov.uk/environment-agency
© Environment Agency 2017
2
Rainfall
October 2016
November 2016
December 2016
January 2017
February 2017
March 2017
April 2017
May 2017
June 2017
July 2017
August 2017
September 2017
Figure 1.1: Monthly rainfall across England and Wales for the past 12 months. UKPP radar data (Source: Met Office © Crown Copyright, 2017). Note: Radar beam blockages in some regions may give anomalous totals in some areas. Crown copyright. All rights reserved. Environment Agency, 100026380, 2017.
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© Environment Agency 2017
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Figure 1.2: Total rainfall for hydrological areas across England for the current month (up to 30 September), 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, 2017). 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, 2017.
www.gov.uk/environment-agency
© Environment Agency 2017
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Rainfall charts
Below average rainfall Above average rainfall
300%
Central England East England
300%
250%
250%
200%
200%
150%
150%
100%
100%
50%
50%
0%
0%
Mar-17
Apr-17
May-17
Jun-17
Jul-17
Aug-17
Sep-17
Mar-17
Apr-17
May-17
Jun-17
Jul-17
Aug-17
Sep-17
Jan-17
Feb-17
Mar-17
Apr-17
May-17
Jun-17
Jul-17
Aug-17
Sep-17
Oct-15
Nov-15
Dec-15
Jan-16
Feb-16
Mar-16
Apr-16
May-16
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-17
Jul-17
Aug-17
Sep-17
Oct-15
Nov-15
Dec-15
Jan-16
Feb-16
Mar-16
Apr-16
May-16
Jun-16
Jul-16
Aug-16
Sep-16
Oct-16
Nov-16
Dec-16
Feb-17
Dec-16
Feb-17
Dec-16
0%
Nov-16
0%
Oct-16
50%
Sep-16
50%
Aug-16
100%
Jul-16
100%
Jan-17
South-west England South-east England
Jun-16
150%
May-16
150%
Apr-16
200%
Mar-16
200%
Feb-16
250%
Jan-16
250%
Dec-15
300%
Nov-15 Oct-15
Sep-17 Aug-17 Jul-17 Jun-17 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-16
Apr-16 Mar-16 Feb-16 Jan-16 Dec-15
Nov-15 Oct-15 300%
Nov-16
0%
Oct-16
0%
Sep-16
50%
Aug-16
50%
Jul-16
100%
Jun-16
100%
May-16
150%
Apr-16
150%
Mar-16
200%
Feb-16
200%
Jan-16
250%
Dec-15
250%
Nov-15 Oct-15
Sep-17 Aug-17 Jul-17 Jun-17 May-17 Apr-17 Mar-17 Feb-17
300%
Jan-17
North-west England North-east England
Sep-17
Aug-17
Jul-17
Jun-17
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-16
Apr-16
Mar-16
Feb-16
Jan-16
Dec-15
Nov-15
Oct-15
5
© Environment Agency 2017
www.gov.uk/environment-agency
Jan-17 Dec-16 Nov-16 Oct-16 Sep-16
Aug-16 Jul-16 Jun-16 May-16
Apr-16 Mar-16 Feb-16 Jan-16 Dec-15
Nov-15 Oct-15 300%
300%
England
250%
200%
150%
100%
50%
0%
Figure 1.3: Monthly rainfall totals for the past 24 months as a percentage of the 1961 – 1990 long term average for each region and for England. NCIC (National Climate Information Centre) data. (Source: Met Office © Crown Copyright, 2017).
Soil moisture deficit End of August 20171
End of September 20172
Figure 2.1: Soil moisture deficits for weeks ending 29 August 2017 1 (left panel) and 3 October 2017 2 (right panel). Top row shows actual soil moisture deficits (mm) and bottom row shows the difference (mm) of the actual from the 1961-90 long term average soil moisture deficits. MORECS data for real land use (Source: Met Office © Crown Copyright, 2017). Crown copyright. All rights reserved. Environment Agency, 100026380, 2017
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© Environment Agency 2017
6
Soil moisture deficit charts Central England 0
10
10
20
20
Soil moisture deficit (mm)
Soil moisture deficit (mm)
East England 0
30 40 50 60 70 80 90
30 40 50 60 70 80 90
100
100
110
110
120
120
130
140 May
130
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb Mar
Apr
May
Jun
Jul
Aug
Sep
140 May
Oct
Jun
Jul
Aug
Sep
Oct
Nov
0
10
10
20
20
30
40 50 60 70 80
May
Jun
Jul
Aug
Sep
Oct
Jun
Jul
Aug
Sep
Oct
Jun
Jul
Aug
Sep
Oct
30 40 50 60 70
110
100
120
110
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb Mar
Apr
May
Jun
Jul
Aug
Sep
120 May
Oct
Jun
Jul
Aug
Sep
Oct
Nov
South-east England
Dec
Jan
Feb Mar
Apr
May
South-west England
0
0
10
10
20
20
30
Soil moisture deficit (mm)
Soil moisture deficit (mm)
Apr
90
100
40
50 60 70 80 90 100 110
30 40 50 60 70 80 90 100
120
110
130
120
140
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150
160 May
Feb Mar
80
90
130 May
Jan
North-west England
0
Soil moisture deficit (mm)
Soil moisture deficit (mm)
North-east England
Dec
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb Mar
Apr
Below minimum monthly level
May
Jun
Jul
Aug
Sep
Oct
Above maximum monthly level
140 May
Jun
Jul
────
Aug
Sep
Oct
Nov
Average
Dec
Jan
Feb Mar
Apr
────
May
Latest data
Figure 2.2: Latest soil moisture deficits for all geographic regions compared to maximum, minimum and 1961-90 long term average. Weekly MORECS data for real land use. (Source: Met Office © Crown Copyright, 2017).
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© Environment Agency 2017
7
River flows
^
“Naturalised” flows are provided for the River Thames at Kingston and the River Lee at Feildes Weir
*
Data for the River Coln at Bibury is currently under investigation Underlined sites are regional index sites and are shown on the hydrographs in Figure 3.2
Figure 3.1: Monthly mean river flow for indicator sites for August 2017 and September 2017, expressed as a percentage of the respective long term average and classed relative to an analysis of historic August and September monthly means (Source: Environment Agency). Crown copyright. All rights reserved. Environment Agency, 100026380, 2017.
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© Environment Agency 2017
8
River flow charts Exceptionally high Below normal ─ ─ ─ Monthly maximum
Notably high Notably low ─── Latest data
Above normal Exceptionally low ─ ─ ─ Monthly minimum
Offord, BEDFORD OUSE Ranking derived from data for the period Jan-1970 to Dec-2012
Normal
Marston-on-Dove, DOVE Ranking derived from data for the period Jul-1965 to Dec-2012
120
50
Flow (cumecs)
Flow (cumecs)
100 80
60 40 20 0 Dec-16
40 30 20 10
Feb-17
Apr-17
Jun-17
Aug-17
0 Dec-16
Oct-17
Haydon Bridge, SOUTH TYNE Ranking derived from data for the period Oct-1974 to Dec-2012
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
Caton, LUNE Ranking derived from data for the period Jan-1959 to Dec-2012 140 120
50
Flow (cumecs)
Flow (cumecs)
60
40 30 20 10 0 Dec-16
Feb-17
Apr-17
Jun-17
Aug-17
60 40
0 Dec-16
Oct-17
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
Kingston, THAMES Ranking derived from data for the period Jan-1883 to Dec-2012
16
350
14
300
12
Flow (cumecs)
Flow (cumecs)
80
20
Horton, GREAT STOUR Ranking derived from data for the period Oct-1964 to Dec-2012
10 8 6 4
250 200 150 100 50
2 0 Dec-16
100
Feb-17
Apr-17
Jun-17
Aug-17
0 Dec-16
Oct-17
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
Thorverton, EXE Ranking derived from data for the period Apr-1956 to Dec-2012 70
Flow (cumecs)
60 50 40
30 20 10 0 Dec-16
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
Figure 3.2: Index river flow sites for each geographic region. Monthly mean flow compared to an analysis of historic monthly mean flows, long term maximum and minimum flows. (Source: Environment Agency).
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© Environment Agency 2017
9
Groundwater levels
^ The level at Priors Heyes remains high compared to historic levels because the aquifer is recovering from the effects of historic abstraction ^^ Sites are manually dipped at different times during the month. They may not be fully representative of levels at the month end Underlined sites are major aquifer index sites and are shown in the groundwater level charts in Figure 4.2
Figure 4.1: Groundwater levels for indicator sites at the end of August 2017 and September 2017, classed relative to an analysis of respective historic August and September levels (Source: Environment Agency). Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC. Crown copyright. All rights reserved. Environment Agency, 100026380, 2017.
www.gov.uk/environment-agency
© Environment Agency 2017
10
Groundwater level charts Exceptionally high Below normal ─ ─ ─ Monthly maximum
Notably high Notably low ─── Latest data
Above normal Exceptionally low ─ ─ ─ Monthly minimum
Normal
Redlands Hall (Chalk)
Heathlanes (Sandstone)
Ranking derived from data for the period Aug-1963 to Dec-2012
Ranking derived from data for the period Jul-1971 to Dec-2012
66
56
65
Level (mAOD)
Level (mAOD)
51 46 41 36
64 63 62
61 60
31 Dec-15 Mar-16 Jun-16
Sep-16 Dec-16 Mar-17 Jun-17
59 Dec-15 Mar-16 Jun-16
Sep-17
Sep-16 Dec-16 Mar-17 Jun-17
Sep-17
Dalton Holme (Chalk)
Skirwith (Sandstone)
Ranking derived from data for the period Jan-1889 to Dec-2012
Ranking derived from data for the period Oct-1978 to Dec-2012
25
133 132
21
Level (mAOD)
Level (mAOD)
23
19 17 15 13
131 130 129
11
9 Dec-15 Mar-16 Jun-16
Sep-16 Dec-16 Mar-17 Jun-17
128 Dec-15 Mar-16 Jun-16
Sep-17
Chilgrove (Chalk)
Little Bucket (Chalk) Ranking derived from data for the period Jan-1971 to Dec-2012
85
72
80
67
Level (mAOD)
Level (mAOD)
Sep-17
Ranking derived from data for the period Feb-1836 to Dec-2012 77
62 57 52 47 42
75 70 65 60
37 32 Dec-15 Mar-16 Jun-16
Sep-16 Dec-16 Mar-17 Jun-17
55 Dec-15 Mar-16 Jun-16
Sep-17
Sep-16 Dec-16 Mar-17 Jun-17
Sep-17
Jackaments Bottom (Jurassic Limestone)
Stonor Park (Chalk)
Ranking derived from data for the period Jan-1974 to Dec-2012
Ranking derived from data for the period May-1961 to Dec-2012
107
90
105 103
Level (mAOD)
Level (mAOD)
Sep-16 Dec-16 Mar-17 Jun-17
101 99 97 95
80 75
70 65
93 91 Dec-15 Mar-16 Jun-16
85
Sep-16 Dec-16 Mar-17 Jun-17
Sep-17
60 Dec-15 Mar-16 Jun-16
Sep-16 Dec-16 Mar-17 Jun-17
Sep-17
Figure 4.2: Index groundwater level sites for major aquifers. End of month groundwater levels months compared to an analysis of historic end of month levels and long term maximum and minimum levels. (Source: Environment Agency, 2017).
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© Environment Agency 2017
11
Reservoir storage
1. Engineering work at Abberton Reservoir in east England to increase capacity has been completed 2. Vyrnwy, Clywedog and Elan Valley reservoirs are located in Wales but provide a water resource to central and north-west England 3. Current levels at Kielder will be deliberately lower than historical levels during a trial of a new flood alleviation control curve
Figure 5.1: Reservoir stocks at key individual and groups of reservoirs at the end of August and September 2017 as a percentage of total capacity and classed relative to an analysis of historic August and September values respectively (Source: Water Companies). Note: Classes shown may not necessarily relate to control curves or triggers for drought actions. As well as for public water supply, some reservoirs are drawn down to provide flood storage, river compensation flows or for reservoir safety inspections. In some cases current reservoir operating rules may differ from historic ones. Crown copyright. All rights reserved. Environment Agency, 100026380, 2017.
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© Environment Agency 2017
12
East England
Central England
Based on storage in Abberton, Grafham, Hanningfield, Rutland reservoirs
Based on storage in Clywedog, Carsington and Ogston, Derwent Valley, Dove (Foremark & Staunton), Draycote, Elan Valley Group reservoirs
100
100
90
90
Percentage of total capacity
Percentage of total capacity
Reservoir storage charts
80 70 60 50 40
60 50 40 30
20
20
10
10
Jul
Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Jul
0 Feb Mar Apr May Jun
Aug Sep Oct
Jul
Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Jul
North-east England
North-west England
Based on storage in Kielder, Teesdale Group, Yorkshire Supply Group reservoirs
Based on storage in NCZ Regional Group, Pennines Group, Vyrnwy reservoirs
100
100
90
90
Percentage of total capacity
Percentage of total capacity
70
30
0 Feb Mar Apr May Jun
80 70 60 50 40
70 60 50 40 30
20
20
10
10
Jul
Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Jul
0 Feb Mar Apr May Jun
Aug Sep Oct
Aug Sep Oct
80
30
0 Feb Mar Apr May Jun
Jul
Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Jul
Aug Sep Oct
South-east England
South-west England
Based on storage in Ardingly, Bewl, Bough Beech, Farmoor, Lower Lee Group, Lower Thames Group reservoirs
Based on storage in Blagdon, Chew Valley, Clatworthy, Colliford, Roadford, Stithians, Wimbleball reservoirs
100
100
90
90
Percentage of total capacity
Percentage of total capacity
80
80 70 60 50 40
80 70 60 50 40
30
30
20
20
10
10
0 Feb Mar Apr May Jun
Jul
Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Jul
Aug Sep Oct
0 Feb Mar Apr May Jun
Jul
Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Jul
Aug Sep Oct
Jul
Aug Sep Oct
England Based on combined regional storage 100
Percentage of total capacity
90 80 70 60 50 40 30 20 10 0 Feb Mar Apr May Jun
Below minimum monthly level
Jul
Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Above maximum monthly level
────
Average
────
Latest data
Figure 5.2: Regional reservoir stocks. End of month reservoir stocks compared to long term maximum, minimum and average stocks (Source: Water Companies). Note: Historic records of individual reservoirs/reservoir groups making up the regional values vary in length.
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© Environment Agency 2017
13
Forward look – river flow Rainfall greater than 120% LTA during Oct to Mar has occurred in 16% to 27% of years¹ in the historic record (since 1910)
(a)
Rainfall greater than 100% LTA during Oct to Mar has occurred in 53% to 58% of years¹ in the historic record (since 1910)
(b)
Rainfall less than 60% LTA during Oct to Mar has occurred in less than 2% of years¹ in the historic record (since 1910)
Rainfall less than 80% LTA during Oct to Mar has occurred in 9% to 15% of years¹ in the historic record (since 1910)
(c)
(d)
Figure 6.1: Projected river flows at key indicator sites up until the end of March 2018. Projections based on four scenarios: 120% (a), 100% (b), 80% (c) and 60% (d) of long term average rainfall between October 2017 and March 2018 (Source: Centre for Ecology and Hydrology, Environment Agency). 1
This range of probabilities is a regional analysis Projections for these sites are produced by CEH 3 Projections for these sites are produced by the Environment Agency ^ “Naturalised” flows are projected for these sites 2
www.gov.uk/environment-agency
© Environment Agency 2017
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Rainfall greater than 120% LTA during Oct to Sep has occurred in 9% to 18% of years¹ in the historic record (since 1910)
Rainfall greater than 100% LTA during Oct to Sep has occurred in 58% to 64% of years¹ in the historic record (since 1910)
(b)
(a)
Rainfall less than 80% LTA during Oct to Sep has occurred in 2% to 8% of years¹ in the historic record (since 1910)
(c)
Rainfall less than 60% LTA during Oct to Sep has occurred in less than 1% of years¹ in the historic record (since 1910)
(d)
Figure 6.2: Projected river flows at key indicator sites up until the end of September 2018. Projections based on four scenarios: 120% (a), 100% (b), 80% (c) and 60% (d) of long term average rainfall between October 2017 and September 2018 (Source: Centre for Ecology and Hydrology, Environment Agency). 1
This range of probabilities is a regional analysis Projections for these sites are produced by CEH Projections for these sites are produced by the Environment Agency ^ “Naturalised” flows are projected for these sites 2 3
www.gov.uk/environment-agency
© Environment Agency 2017
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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.
Figure 6.3: Probabilistic ensemble projections of river flows at key indicator sites up until the end of March 2018. 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). 1
Projections for these sites are produced by the Environment Agency Projections for these sites are produced by CEH ^“Naturalised” flows are projected for these sites 2
www.gov.uk/environment-agency
© Environment Agency 2017
16
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.
Figure 6.4: Probabilistic ensemble projections of river flows at key indicator sites up until the end of September 2018. 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). 1
Projections for these sites are produced by the Environment Agency Projections for these sites are produced by CEH ^“Naturalised” flows are projected for these sites 2
www.gov.uk/environment-agency
© Environment Agency 2017
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Forward look - groundwater Rainfall greater than 120% LTA during Oct to Mar has occurred in 16% to 27% of years¹ in the historic record (since 1910) )
Rainfall greater than 100% LTA during Oct to Mar has occurred in 53% to 58% of years¹ in the historic record (since 1910)
(b)
(a)
Rainfall less than 80% LTA during Oct to Mar has occurred in 9% to 15% of years¹ in the historic record (since 1910)
(c)
Rainfall less than 60% LTA during Oct to Mar has occurred in less than 2% of years¹ in the historic record (since 1910)
(d)
Figure 6.5: Projected groundwater levels at key indicator sites at the end of March 2018. Projections based on four scenarios: 120% (a), 100% (b), 80% (c) and 60% (d) of long term average rainfall between October 2017 and March 2018 (Source: Environment Agency). Geological map reproduced with kind permission from UK Groundwater Forum BGS © NERC. Crown copyright all rights reserved. Environment Agency 100026380, 2017. * Projections for these sites are produced by BGS 1 This range of probabilities is a regional analysis
www.gov.uk/environment-agency
© Environment Agency 2017
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Rainfall greater than 120% LTA during Oct to Sep has occurred in 9% to 18% of years¹ in the historic record (since 1910)
Rainfall greater than 100% LTA during Oct to Sep has occurred in 58% to 64% of years¹ in the historic record (since 1910)
(b)
(a)
Rainfall less than 80% LTA during Oct to Sep has occurred in 2% to 8% of years¹ in the historic record (since 1910)
(c)
Rainfall less than 60% LTA during Oct to Sep has occurred in less than 1% of years¹ in the historic record (since 1910)
(d)
Figure 6.6: Projected groundwater levels at key indicator sites at the end of September 2018. Projections based on four scenarios: 120% (a), 100% (b), 80% (c) and 60% (d) of long term average rainfall between October 2017 and September 2018 (Source: Environment Agency). Geological map reproduced with kind permission from UK Groundwater Forum BGS © NERC Crown copyright. All rights reserved. Environment Agency 100026380 2017. * Projections for these sites are produced by BGS 1 This range of probabilities is a regional analysis www.gov.uk/environment-agency
© Environment Agency 2017
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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.
Figure 6.7: Probabilistic ensemble projections of groundwater levels at key indicator sites at the end of March 2018. 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. * Projections for these sites are produced by BGS
www.gov.uk/environment-agency
© Environment Agency 2017
20
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.
Figure 6.8: Probabilistic ensemble projections of groundwater levels at key indicator sites at the end of September 2018. 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. * Projections for these sites are produced by BGS www.gov.uk/environment-agency
© Environment Agency 2017
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Figure 7.1: Geographic regions Crown copyright. All rights reserved. Environment Agency, 100026380, 2017.
www.gov.uk/environment-agency
© Environment Agency 2017
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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. For rainfall and soil moisture deficit, the period refers to 1961-1990, unless otherwise stated. For other parameters, the period may vary according to data availability
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
www.gov.uk/environment-agency
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
