Water Situation Report Simple Storage Service
Monthly Water Situation Report North West England Summary – September 2017 Table 1. North West England summary of the current water situation.
Parameter
Current status
Rainfall
North West England rainfall was 145% of September’s Long Term Average (LTA). Classed as ‘Above Normal’ this month. SMD levels generally fell across North West England with the only exceptions being noted in the north-westerly areas where relatively small increases were observed. Classed between ‘Above Normal’ and ‘Notably High’. Classed between ‘Normal’ and ‘Exceptionally High’. Total North West England reservoir storage increased from 83% (end of August) to 86% (end of September).
Soil Moisture Deficit (SMD) River Flows Groundwater Levels Reservoir Storage Rainfall
Rainfall for North West England was classed as ‘Above Normal’ (145% of the LTA) for September, with seven out of ten hydrological areas experiencing a fourth or fifth successive month of above average rainfall (Figure 2). Rainfall was classed as either ‘Above Normal’ or ‘Notably High’ in all but two hydrological areas; the exceptions being the Derwent (121% of the LTA, classed as ‘Normal’) and the Esk (Dumfries) (100% of the LTA, classed as ‘Normal’). When compared to the LTA, the highest rainfall was observed in the Cheshire Rivers Group area (163% of the LTA) and the lowest in the Esk (Dumfries) (100% of the LTA) (Figure 3). Many areas of North West England experienced heavy rainfall in the lead up to and during Storm Aileen (12 September). The ‘Notably High’ rainfall observed in the Greater Manchester, Merseyside and Cheshire area in September has particularly affected the classification of the 3 month cumulative rainfall totals in this area when compared to last month. These are now classed as ‘Above Normal’ compared to ‘Normal’ at the end of August. The twelve month cumulative rainfall total for the Esk (Dumfries) has now been classed as either ‘Below Normal’, ‘Notably Low’ or ‘Exceptionally Low’ every month since December 2016.
Soil Moisture Deficit/Recharge SMD levels generally fell across North West England with the only exceptions being noted in the north-westerly areas where relatively small increases were observed (Figure 4). The majority of areas had SMD levels below 10mm and all areas ended the month with SMD levels lower than the long term average values for September. The highest SMD levels were again observed in the Wirral, Weaver and Gowy catchments.
River Flows River flows generally increased across North West England when compared to last month (Figure 5) and were all classed as either ‘Above Normal’ or ‘Notably High’. The only exception to this was noted in the Derwent catchment which experienced relatively lower rainfall than most other catchments. A few rivers observed notable peaks in flow around the time of Storm Aileen (12 September) e.g. the River Lune at Caton gauging station recorded a peak equivalent to above Q1 flow (i.e. this flow has been exceeded less than 1% of the time at this gauging station) on 13 September. River flows were highest (when compared to the LTA for September) in the Wyre catchment (224% of LTA) and lowest in the Weaver (111% of LTA) (Figure 6). The flows in the Weaver appear lower than might have been expected given the relatively high rainfall in the area. This could be due to the higher antecedent SMD levels in this catchment.
Groundwater Levels Groundwater levels for September remained classed as between ‘Normal’ and ‘Exceptionally High’ (Figure 7), with one change in classification since the end of August observed at Brown Bank Lay-By (now classed as ‘Exceptionally High’ compared to ‘Notably High’ last month). Crow Lady Farm and Skirwith were both classed as ‘Normal’, while (Summary continued on next page.)
Go to the Glossary
AllAll data are provisional and may bebe subject toto revision. views expressed in in this document are not necessarily those ofof the data are provisional and may subject revision.The The views expressed this document are not necessarily those the Environment Agency. ItsIts officers, servants oror agents accept nono liability forfor any loss oror damage arising from the interpretation oror Environment Agency. officers, servants agents accept liability any loss damage arising from the interpretation use ofof the information, oror reliance upon views contained herein. use the information, reliance upon views contained herein. © Environment Agency 2014
© Environment Agency 2017
Groundwater Levels (continued) Bruntwood Hall, Priors Heyes and Yew Tree Farm were all classed as ‘Exceptionally High’ (Figure 8). The levels at Priors Heyes and Yew Tree Farm remain high compared to historic levels because the aquifer is recovering from the effects of historically high abstractions.
Reservoir Storage/Water Resource Zone Stocks Reservoir stocks for North West England increased from 83% at the end of August to 86% at the end of September (Figure 10). At the end of September, reservoir stocks were highest at Vyrnwy (97%), lowest at Thirlmere (74%), with the reservoir stock at Haweswater at 75% (Figure 1). Reservoir stocks were generally higher than average for the time of year. Chelburn Upper, Clowbridge, Earnsdale, Heaton Park Open, Kitcliffe, Rhodeswood, Swinden No 1 and Warland were kept low for maintenance works.
Figure 1: Storage in Haweswater reservoir including the drought triggers for the reservoir and storage for representative years; 1995, 2003, 2010 and 2016.
Picture 1: The River Irk at Collyhurst Weir gauging station on 11 September 2017 at 10:51. Photo taken by Barrie Scholes (Greater Manchester, Merseyside and Cheshire Hydrometry and Telemetry Team). The flow being measured using the equipment shown was 26.7m3/s which is above Q1 and is the highest spot flow measurement taken at this gauging station (open since 1995). N.B. This is not the highest flow on record at the station. Author: Rachel Kewley Contact details: North West Hydrology
2
Rainfall
Crown Copyright. All rights reserved. Environment Agency, 1000026380, 2017
Figure 2. Total rainfall (as a percentage) for hydrological areas across North West England for the current month, the last three months, the last six months, and the last 12 months, classed relative to an analysis of respective historic totals. 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.
3
Rainfall Above average rainfall
Below average rainfall 1-Month Period for Cumbria and Lancashire (Cumbria)
1-Month Period for North West England
50%
0%
0% Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
1-Month Period for Greater Manchester, Merseyside and Cheshire
1-Month Period for Cumbria and Lancashire (Lancashire)
400%
Sep-17
50%
Aug-17
100%
Jul-17
100%
Jun-17
150%
May-17
200%
150%
Apr-17
250%
200%
Mar-17
250%
Feb-17
300%
Jan-17
350%
300%
Dec-16
350%
Nov-16
400%
Oct-16
400%
400%
350%
350%
300%
300% 250% 250% 200%
200%
150%
150%
100%
100%
50%
50%
0%
Aug-17
Sep-17
Aug-17
Sep-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
1-Month Period for Esk (Cumbria)
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
0%
1-Month Period for Derwent (NW)
400%
400%
350%
350%
300%
300%
250%
250%
200%
200%
150%
150%
100%
100%
50%
50%
0%
Jul-17
Jun-17
May-17
Apr-17
Mar-17
1-Month Period for Eden
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
0%
1-Month Period for Esk (Dumfries)
Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
Feb-17
Jan-17
Dec-16
Nov-16
4
Oct-16
Sep-17
Aug-17
0%
Jul-17
50%
0% Jun-17
100%
50%
May-17
150%
100%
Apr-17
200%
150%
Mar-17
250%
200%
Feb-17
300%
250%
Jan-17
350%
300%
Dec-16
350%
Nov-16
400%
Oct-16
400%
Rainfall Above average rainfall
Below average rainfall
1-Month Period for Cheshire Rivers Group
1-Month Period for Kent
400%
400%
350%
350%
300%
300%
250%
250%
200%
200%
150%
150%
100%
100%
50%
50%
0%
Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
1-Month Period for Mersey and Irwell
400%
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
0%
1-Month Period for Douglas 400%
350%
350%
300%
300%
250%
250%
200%
200%
150%
150%
100%
100%
50%
50% 0% Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
1-Month Period for Ribble
Feb-17
Jan-17
Dec-16
Nov-16
Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
Oct-16
0%
1-Month Period for Wyre and Lune
400%
400%
350%
350%
300%
300%
Figure 3: Monthly rainfall totals for the past 12 months expressed as a percentage of the long term average (1961-90), for North West England and its hydrological areas using 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.
5
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-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
0%
Mar-17
50%
0% Feb-17
100%
50%
Jan-17
150%
100%
Dec-16
200%
150%
Nov-16
250%
200%
Oct-16
250%
Soil Moisture Deficit
Crown Copyright. All rights reserved. Environment Agency, 1000026380, 2017
Figure 4: Soil moisture deficits for weeks ending 30 August 20171 (left panel) and 27 September 20172 (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). 6
River Flow
Crown Copyright. All rights reserved. Environment Agency, 1000026380, 2017
Figure 5: Monthly mean river flow for this month, expressed as a percentage of the month’s long term average and classed relative to analysis of historic monthly means (Source: Environment Agency). 7
River Flow Exceptionally high Below normal
Notably high Notably low
Above normal Exceptionally low
Ashbrook, WEAVER (NW)
Ashton Weir, MERSEY
Ranking derived from data for the period Oct-1937 to Dec-2012
Ranking derived from data for the period Jun-1976 to Dec-2012
21
40
18
35 30
Flow (m3/s)
15
Flow (m3/s)
Normal ─── Latest data
12
9 6
20 15 10
3 0 Dec-16
25
5 Feb-17
Apr-17
Jun-17
Aug-17
0 Dec-16
Oct-17
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
Caton, LUNE
Newby Bridge Fms, LEVEN (NW)
Ranking derived from data for the period Jan-1959 to Dec-2012
Ranking derived from data for the period Jan-1939 to Dec-2012
125
40 35 30
Flow (m3/s)
Flow (m3/s)
100
75 50
25 20 15 10
25
5 Feb-17
Apr-17
Jun-17
Aug-17
0 Dec-16
Oct-17
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
Ouse Bridge, DERWENT (NW)
Pooley Bridge Upstream, EAMONT
Ranking derived from data for the period Mar-1968 to Dec-2012
Ranking derived from data for the period Jul-1970 to Dec-2012
60
30
50
25
40
20
Flow (m3/s)
Flow (m3/s)
0 Dec-16
30 20 10 0 Dec-16
15 10 5
Feb-17
Apr-17
Jun-17
Aug-17
0 Dec-16
Oct-17
8
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
River Flow Exceptionally high Below normal
Notably high Notably low
Above normal Exceptionally low
Normal ─── Latest data
Samlesbury Pgs, RIBBLE (NW)
Sheepmount, EDEN (NW)
Ranking derived from data for the period May-1960 to Dec-2012
Ranking derived from data for the period Oct-1967 to Dec-2012
120
200
100
Flow (m3/s)
Flow (m3/s)
150 80
60 40
100
50 20 0 Dec-16
Feb-17
Apr-17
Jun-17
Aug-17
0 Dec-16
Oct-17
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
St Michaels Fms, WYRE Ranking derived from data for the period Oct-1963 to Dec-2012 25
Flow (m3/s)
20
15 10 5 0 Dec-16
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
Figure 6: Monthly mean river flows for the past 10 months for sites across North West England (Source: Environment Agency). There is no flow record from Camerton following damage caused by the floods in November 2009. The Gauging Station at Ouse Bridge replaces this for the Derwent catchment. Flow for Sheepmount has been estimated due to uncertainty in the current rating following the December 2015 floods and so should be treated with some caution.
9
Groundwater Levels
Crown Copyright. All rights reserved. Environment Agency, 1000026380, 2017
Figure 7: Groundwater levels at the end of the month classed relative to an analysis of historic groundwater levels for the same month (Source: Environment Agency). Geological map reproduced with kind permission from the UK Groundwater Forum, British Geological Survey (BGS) © Natural Environment Research Council (NERC). Groundwater levels for Bruntwood Hall have been estimated (the site is temporarily out of commission) and so should be treated with some caution. 10
Groundwater Levels Exceptionally high Below normal
Notably high Notably low
Above normal Exceptionally low
BROWN BANK LAY-BY
BRUNTWOOD HALL OBH
Ranking derived from data for the period Jul-1974 to Dec-2012
Ranking derived from data for the period Dec-1972 to Dec-2012
26.0
49.5 49.0
Level (mAOD)
Level (mAOD)
25.5 25.0 24.5 24.0
23.0 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17 Aug-17
48.0
47.0 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17 Aug-17
Crow Lady Farm T74
PRIORS HEYES
Ranking derived from data for the period Apr-1973 to Dec-2012
Ranking derived from data for the period Sep-1972 to Dec-2012
33.0
11.0
32.5
Level (mAOD)
11.5
10.5 10.0 9.5
9.0
32.0 31.5 31.0
8.5
30.5
8.0 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17 Aug-17
30.0 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17 Aug-17
SKIRWITH
YEW TREE FARM
Ranking derived from data for the period Oct-1978 to Dec-2012
Ranking derived from data for the period Jun-1971 to Dec-2012
132.0
15.5
131.5
15.0
Level (mAOD)
Level (mAOD)
48.5
47.5
23.5
Level (mAOD)
Normal ─── Latest data
131.0 130.5 130.0
14.5 14.0 13.5
13.0
129.5
12.5
129.0 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17 Aug-17
12.0 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17 Aug-17
Figure 8: End of month groundwater levels for the past 34 months for North West England groundwater sites (Source: Environment Agency).
11
Reservoir Stocks
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Figure 9: The location of reservoirs that comprise the supply districts across North West England and selected individual reservoirs. 12
Reservoir Stocks
Total North West England Reservoir Stocks
90
90
80
80
70 60 50 40 30 20
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
50 40
30 20
Jan
Dec
North area supply district: Lakes
100
Feb
Mar
90
90
80
80
70 60 50
40 30 20 10
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Oct
Nov
Dec
Oct
Nov
Dec
Oct
Nov
Dec
Pennine supply district (East)
100
Percentage of live capacity
Percentage of live capacity
60
0
0
70 60 50 40 30 20 10
0
0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Pennine supply district (West)
100
Feb
Mar
90
90
80
80
70 60 50 40
30 20 10
Apr
May
Jun
Jul
Aug
Sep
Pennine NCZ (East and West)
100
Percentage of live capacity
Percentage of live capacity
70
10
10
70 60 50 40 30 20 10
0
0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Peak supply district: Longdendale
100
Feb
Mar
90
90
80
80
70 60 50 40 30 20
Apr
May
Jun
Jul
Aug
Sep
Peak supply district: Stockport
100
Percentage of live capacity
Percentage of live capacity
North area supply district: Ribble
100
Percentage of live capacity
Percentage of live capacity
100
70 60 50 40 30 20 10
10
0
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Jan
Dec
13
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Reservoir Stocks
Rivington Group
Vyrnwy Reservoir
100
90
90
80
80
Percentage of live capacity
Percentage of live capacity
100
70 60 50 40 30 20
70 60 50 40 30 20 10
10
0
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Jan
Dec
Feb
Mar
Apr
May
Thirlmere Reservoir
100
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Ennerdale Water Trigger 1
Trigger 2
Trigger 3
Trigger 4
-1.0
90
-0.5 70
Level (mBTWL)
Percentage of live capacity
80
60 50
40 30
0.0
0.5
1.0
20 1.5 10
0
2.0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
Crummock Water Trigger 2
Trigger 3
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Haweswater Reservoir Trigger 1
Trigger 4
100
100
90
90
80
80
Percentage of live capacity
Percentage of live capacity
Trigger 1
May
70 60 50 40 30 20 10
Trigger 2
Trigger 3
Drought Permit Application Indicator
Trigger 4
70 60 50 40 30 20
10 0
0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Jan
Dec
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Figure 10: End of month reservoir stocks for supply districts across North West England and selected individual reservoirs for current and representative years; 1995, 2003, 2010 and 2016 (Source: United Utilities).
14
Glossary Term
Definition
Aquifer Areal average rainfall
A geological formation able to store and transmit water. The estimated average depth of rainfall over a defined area. Expressed in depth of water (mm). 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. Borehole where the level of groundwater is above the top of the borehole and groundwater flows out of the borehole when unsealed. The rainfall available to percolate into the soil or produce river flow. Expressed in depth of water (mm). 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. The water found in an aquifer 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). Met Office Rainfall and Evaporation Calculation System. This is a generic name for Met. Office services involving the routine calculation of soil moisture and evaporation for Great Britain and uses a grid of 40 x 40 km squares. River flow with the impacts of artificial influences removed. Artificial influences may include abstractions, discharges, transfers, augmentation and impoundments. National Climate Information Centre. NCIC area monthly rainfall totals are derived using the Met Office 5 km gridded dataset, which uses rain gauge observations. The process of increasing the water stored in the saturated zone of an aquifer. Expressed in depth of water (mm). The total capacity of a reservoir. The reservoir capacity normally usable for storage to meet established reservoir operating requirements. The difference between the amount of water actually in the soil and the amount of water that the soil can hold. Expressed in depth of water (mm).
Artesian Artesian Borehole Effective rainfall Flood Alert/Flood warning
Groundwater Long Term Average (LTA)
MORECS
Naturalised Flow NCIC Recharge Reservoir gross capacity Reservoir live capacity Soil moisture deficit (SMD)
Categories for rainfall, river flows, groundwater levels Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low
Value likely to fall within this band 5% of the time Value likely to fall within this band 8% of the time Value likely to fall within this band 15% of the time Value likely to fall within this band 44% of the time Value likely to fall within this band 15% of the time Value likely to fall within this band 8% of the time Value likely to fall within this band 5% of the time
Units mAOD mBTWL
Metres Above Ordnance Datum (mean sea level at Newlyn Cornwall). meters Below Top Water Level
Return to Summary
15
Parameter
Current status
Rainfall
North West England rainfall was 145% of September’s Long Term Average (LTA). Classed as ‘Above Normal’ this month. SMD levels generally fell across North West England with the only exceptions being noted in the north-westerly areas where relatively small increases were observed. Classed between ‘Above Normal’ and ‘Notably High’. Classed between ‘Normal’ and ‘Exceptionally High’. Total North West England reservoir storage increased from 83% (end of August) to 86% (end of September).
Soil Moisture Deficit (SMD) River Flows Groundwater Levels Reservoir Storage Rainfall
Rainfall for North West England was classed as ‘Above Normal’ (145% of the LTA) for September, with seven out of ten hydrological areas experiencing a fourth or fifth successive month of above average rainfall (Figure 2). Rainfall was classed as either ‘Above Normal’ or ‘Notably High’ in all but two hydrological areas; the exceptions being the Derwent (121% of the LTA, classed as ‘Normal’) and the Esk (Dumfries) (100% of the LTA, classed as ‘Normal’). When compared to the LTA, the highest rainfall was observed in the Cheshire Rivers Group area (163% of the LTA) and the lowest in the Esk (Dumfries) (100% of the LTA) (Figure 3). Many areas of North West England experienced heavy rainfall in the lead up to and during Storm Aileen (12 September). The ‘Notably High’ rainfall observed in the Greater Manchester, Merseyside and Cheshire area in September has particularly affected the classification of the 3 month cumulative rainfall totals in this area when compared to last month. These are now classed as ‘Above Normal’ compared to ‘Normal’ at the end of August. The twelve month cumulative rainfall total for the Esk (Dumfries) has now been classed as either ‘Below Normal’, ‘Notably Low’ or ‘Exceptionally Low’ every month since December 2016.
Soil Moisture Deficit/Recharge SMD levels generally fell across North West England with the only exceptions being noted in the north-westerly areas where relatively small increases were observed (Figure 4). The majority of areas had SMD levels below 10mm and all areas ended the month with SMD levels lower than the long term average values for September. The highest SMD levels were again observed in the Wirral, Weaver and Gowy catchments.
River Flows River flows generally increased across North West England when compared to last month (Figure 5) and were all classed as either ‘Above Normal’ or ‘Notably High’. The only exception to this was noted in the Derwent catchment which experienced relatively lower rainfall than most other catchments. A few rivers observed notable peaks in flow around the time of Storm Aileen (12 September) e.g. the River Lune at Caton gauging station recorded a peak equivalent to above Q1 flow (i.e. this flow has been exceeded less than 1% of the time at this gauging station) on 13 September. River flows were highest (when compared to the LTA for September) in the Wyre catchment (224% of LTA) and lowest in the Weaver (111% of LTA) (Figure 6). The flows in the Weaver appear lower than might have been expected given the relatively high rainfall in the area. This could be due to the higher antecedent SMD levels in this catchment.
Groundwater Levels Groundwater levels for September remained classed as between ‘Normal’ and ‘Exceptionally High’ (Figure 7), with one change in classification since the end of August observed at Brown Bank Lay-By (now classed as ‘Exceptionally High’ compared to ‘Notably High’ last month). Crow Lady Farm and Skirwith were both classed as ‘Normal’, while (Summary continued on next page.)
Go to the Glossary
AllAll data are provisional and may bebe subject toto revision. views expressed in in this document are not necessarily those ofof the data are provisional and may subject revision.The The views expressed this document are not necessarily those the Environment Agency. ItsIts officers, servants oror agents accept nono liability forfor any loss oror damage arising from the interpretation oror Environment Agency. officers, servants agents accept liability any loss damage arising from the interpretation use ofof the information, oror reliance upon views contained herein. use the information, reliance upon views contained herein. © Environment Agency 2014
© Environment Agency 2017
Groundwater Levels (continued) Bruntwood Hall, Priors Heyes and Yew Tree Farm were all classed as ‘Exceptionally High’ (Figure 8). The levels at Priors Heyes and Yew Tree Farm remain high compared to historic levels because the aquifer is recovering from the effects of historically high abstractions.
Reservoir Storage/Water Resource Zone Stocks Reservoir stocks for North West England increased from 83% at the end of August to 86% at the end of September (Figure 10). At the end of September, reservoir stocks were highest at Vyrnwy (97%), lowest at Thirlmere (74%), with the reservoir stock at Haweswater at 75% (Figure 1). Reservoir stocks were generally higher than average for the time of year. Chelburn Upper, Clowbridge, Earnsdale, Heaton Park Open, Kitcliffe, Rhodeswood, Swinden No 1 and Warland were kept low for maintenance works.
Figure 1: Storage in Haweswater reservoir including the drought triggers for the reservoir and storage for representative years; 1995, 2003, 2010 and 2016.
Picture 1: The River Irk at Collyhurst Weir gauging station on 11 September 2017 at 10:51. Photo taken by Barrie Scholes (Greater Manchester, Merseyside and Cheshire Hydrometry and Telemetry Team). The flow being measured using the equipment shown was 26.7m3/s which is above Q1 and is the highest spot flow measurement taken at this gauging station (open since 1995). N.B. This is not the highest flow on record at the station. Author: Rachel Kewley Contact details: North West Hydrology
2
Rainfall
Crown Copyright. All rights reserved. Environment Agency, 1000026380, 2017
Figure 2. Total rainfall (as a percentage) for hydrological areas across North West England for the current month, the last three months, the last six months, and the last 12 months, classed relative to an analysis of respective historic totals. 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.
3
Rainfall Above average rainfall
Below average rainfall 1-Month Period for Cumbria and Lancashire (Cumbria)
1-Month Period for North West England
50%
0%
0% Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
1-Month Period for Greater Manchester, Merseyside and Cheshire
1-Month Period for Cumbria and Lancashire (Lancashire)
400%
Sep-17
50%
Aug-17
100%
Jul-17
100%
Jun-17
150%
May-17
200%
150%
Apr-17
250%
200%
Mar-17
250%
Feb-17
300%
Jan-17
350%
300%
Dec-16
350%
Nov-16
400%
Oct-16
400%
400%
350%
350%
300%
300% 250% 250% 200%
200%
150%
150%
100%
100%
50%
50%
0%
Aug-17
Sep-17
Aug-17
Sep-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
1-Month Period for Esk (Cumbria)
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
0%
1-Month Period for Derwent (NW)
400%
400%
350%
350%
300%
300%
250%
250%
200%
200%
150%
150%
100%
100%
50%
50%
0%
Jul-17
Jun-17
May-17
Apr-17
Mar-17
1-Month Period for Eden
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
0%
1-Month Period for Esk (Dumfries)
Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
Feb-17
Jan-17
Dec-16
Nov-16
4
Oct-16
Sep-17
Aug-17
0%
Jul-17
50%
0% Jun-17
100%
50%
May-17
150%
100%
Apr-17
200%
150%
Mar-17
250%
200%
Feb-17
300%
250%
Jan-17
350%
300%
Dec-16
350%
Nov-16
400%
Oct-16
400%
Rainfall Above average rainfall
Below average rainfall
1-Month Period for Cheshire Rivers Group
1-Month Period for Kent
400%
400%
350%
350%
300%
300%
250%
250%
200%
200%
150%
150%
100%
100%
50%
50%
0%
Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
1-Month Period for Mersey and Irwell
400%
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
0%
1-Month Period for Douglas 400%
350%
350%
300%
300%
250%
250%
200%
200%
150%
150%
100%
100%
50%
50% 0% Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
1-Month Period for Ribble
Feb-17
Jan-17
Dec-16
Nov-16
Sep-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
Mar-17
Feb-17
Jan-17
Dec-16
Nov-16
Oct-16
Oct-16
0%
1-Month Period for Wyre and Lune
400%
400%
350%
350%
300%
300%
Figure 3: Monthly rainfall totals for the past 12 months expressed as a percentage of the long term average (1961-90), for North West England and its hydrological areas using 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.
5
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-17
Aug-17
Jul-17
Jun-17
May-17
Apr-17
0%
Mar-17
50%
0% Feb-17
100%
50%
Jan-17
150%
100%
Dec-16
200%
150%
Nov-16
250%
200%
Oct-16
250%
Soil Moisture Deficit
Crown Copyright. All rights reserved. Environment Agency, 1000026380, 2017
Figure 4: Soil moisture deficits for weeks ending 30 August 20171 (left panel) and 27 September 20172 (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). 6
River Flow
Crown Copyright. All rights reserved. Environment Agency, 1000026380, 2017
Figure 5: Monthly mean river flow for this month, expressed as a percentage of the month’s long term average and classed relative to analysis of historic monthly means (Source: Environment Agency). 7
River Flow Exceptionally high Below normal
Notably high Notably low
Above normal Exceptionally low
Ashbrook, WEAVER (NW)
Ashton Weir, MERSEY
Ranking derived from data for the period Oct-1937 to Dec-2012
Ranking derived from data for the period Jun-1976 to Dec-2012
21
40
18
35 30
Flow (m3/s)
15
Flow (m3/s)
Normal ─── Latest data
12
9 6
20 15 10
3 0 Dec-16
25
5 Feb-17
Apr-17
Jun-17
Aug-17
0 Dec-16
Oct-17
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
Caton, LUNE
Newby Bridge Fms, LEVEN (NW)
Ranking derived from data for the period Jan-1959 to Dec-2012
Ranking derived from data for the period Jan-1939 to Dec-2012
125
40 35 30
Flow (m3/s)
Flow (m3/s)
100
75 50
25 20 15 10
25
5 Feb-17
Apr-17
Jun-17
Aug-17
0 Dec-16
Oct-17
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
Ouse Bridge, DERWENT (NW)
Pooley Bridge Upstream, EAMONT
Ranking derived from data for the period Mar-1968 to Dec-2012
Ranking derived from data for the period Jul-1970 to Dec-2012
60
30
50
25
40
20
Flow (m3/s)
Flow (m3/s)
0 Dec-16
30 20 10 0 Dec-16
15 10 5
Feb-17
Apr-17
Jun-17
Aug-17
0 Dec-16
Oct-17
8
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
River Flow Exceptionally high Below normal
Notably high Notably low
Above normal Exceptionally low
Normal ─── Latest data
Samlesbury Pgs, RIBBLE (NW)
Sheepmount, EDEN (NW)
Ranking derived from data for the period May-1960 to Dec-2012
Ranking derived from data for the period Oct-1967 to Dec-2012
120
200
100
Flow (m3/s)
Flow (m3/s)
150 80
60 40
100
50 20 0 Dec-16
Feb-17
Apr-17
Jun-17
Aug-17
0 Dec-16
Oct-17
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
St Michaels Fms, WYRE Ranking derived from data for the period Oct-1963 to Dec-2012 25
Flow (m3/s)
20
15 10 5 0 Dec-16
Feb-17
Apr-17
Jun-17
Aug-17
Oct-17
Figure 6: Monthly mean river flows for the past 10 months for sites across North West England (Source: Environment Agency). There is no flow record from Camerton following damage caused by the floods in November 2009. The Gauging Station at Ouse Bridge replaces this for the Derwent catchment. Flow for Sheepmount has been estimated due to uncertainty in the current rating following the December 2015 floods and so should be treated with some caution.
9
Groundwater Levels
Crown Copyright. All rights reserved. Environment Agency, 1000026380, 2017
Figure 7: Groundwater levels at the end of the month classed relative to an analysis of historic groundwater levels for the same month (Source: Environment Agency). Geological map reproduced with kind permission from the UK Groundwater Forum, British Geological Survey (BGS) © Natural Environment Research Council (NERC). Groundwater levels for Bruntwood Hall have been estimated (the site is temporarily out of commission) and so should be treated with some caution. 10
Groundwater Levels Exceptionally high Below normal
Notably high Notably low
Above normal Exceptionally low
BROWN BANK LAY-BY
BRUNTWOOD HALL OBH
Ranking derived from data for the period Jul-1974 to Dec-2012
Ranking derived from data for the period Dec-1972 to Dec-2012
26.0
49.5 49.0
Level (mAOD)
Level (mAOD)
25.5 25.0 24.5 24.0
23.0 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17 Aug-17
48.0
47.0 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17 Aug-17
Crow Lady Farm T74
PRIORS HEYES
Ranking derived from data for the period Apr-1973 to Dec-2012
Ranking derived from data for the period Sep-1972 to Dec-2012
33.0
11.0
32.5
Level (mAOD)
11.5
10.5 10.0 9.5
9.0
32.0 31.5 31.0
8.5
30.5
8.0 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17 Aug-17
30.0 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17 Aug-17
SKIRWITH
YEW TREE FARM
Ranking derived from data for the period Oct-1978 to Dec-2012
Ranking derived from data for the period Jun-1971 to Dec-2012
132.0
15.5
131.5
15.0
Level (mAOD)
Level (mAOD)
48.5
47.5
23.5
Level (mAOD)
Normal ─── Latest data
131.0 130.5 130.0
14.5 14.0 13.5
13.0
129.5
12.5
129.0 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17 Aug-17
12.0 Dec-14 Apr-15 Aug-15 Dec-15 Apr-16 Aug-16 Dec-16 Apr-17 Aug-17
Figure 8: End of month groundwater levels for the past 34 months for North West England groundwater sites (Source: Environment Agency).
11
Reservoir Stocks
Crown Copyright. All rights reserved. Environment Agency, 1000026380, 2017
Figure 9: The location of reservoirs that comprise the supply districts across North West England and selected individual reservoirs. 12
Reservoir Stocks
Total North West England Reservoir Stocks
90
90
80
80
70 60 50 40 30 20
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
50 40
30 20
Jan
Dec
North area supply district: Lakes
100
Feb
Mar
90
90
80
80
70 60 50
40 30 20 10
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Oct
Nov
Dec
Oct
Nov
Dec
Oct
Nov
Dec
Pennine supply district (East)
100
Percentage of live capacity
Percentage of live capacity
60
0
0
70 60 50 40 30 20 10
0
0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Pennine supply district (West)
100
Feb
Mar
90
90
80
80
70 60 50 40
30 20 10
Apr
May
Jun
Jul
Aug
Sep
Pennine NCZ (East and West)
100
Percentage of live capacity
Percentage of live capacity
70
10
10
70 60 50 40 30 20 10
0
0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Peak supply district: Longdendale
100
Feb
Mar
90
90
80
80
70 60 50 40 30 20
Apr
May
Jun
Jul
Aug
Sep
Peak supply district: Stockport
100
Percentage of live capacity
Percentage of live capacity
North area supply district: Ribble
100
Percentage of live capacity
Percentage of live capacity
100
70 60 50 40 30 20 10
10
0
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Jan
Dec
13
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Reservoir Stocks
Rivington Group
Vyrnwy Reservoir
100
90
90
80
80
Percentage of live capacity
Percentage of live capacity
100
70 60 50 40 30 20
70 60 50 40 30 20 10
10
0
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Jan
Dec
Feb
Mar
Apr
May
Thirlmere Reservoir
100
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Ennerdale Water Trigger 1
Trigger 2
Trigger 3
Trigger 4
-1.0
90
-0.5 70
Level (mBTWL)
Percentage of live capacity
80
60 50
40 30
0.0
0.5
1.0
20 1.5 10
0
2.0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
Crummock Water Trigger 2
Trigger 3
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Haweswater Reservoir Trigger 1
Trigger 4
100
100
90
90
80
80
Percentage of live capacity
Percentage of live capacity
Trigger 1
May
70 60 50 40 30 20 10
Trigger 2
Trigger 3
Drought Permit Application Indicator
Trigger 4
70 60 50 40 30 20
10 0
0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Jan
Dec
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Figure 10: End of month reservoir stocks for supply districts across North West England and selected individual reservoirs for current and representative years; 1995, 2003, 2010 and 2016 (Source: United Utilities).
14
Glossary Term
Definition
Aquifer Areal average rainfall
A geological formation able to store and transmit water. The estimated average depth of rainfall over a defined area. Expressed in depth of water (mm). 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. Borehole where the level of groundwater is above the top of the borehole and groundwater flows out of the borehole when unsealed. The rainfall available to percolate into the soil or produce river flow. Expressed in depth of water (mm). 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. The water found in an aquifer 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). Met Office Rainfall and Evaporation Calculation System. This is a generic name for Met. Office services involving the routine calculation of soil moisture and evaporation for Great Britain and uses a grid of 40 x 40 km squares. River flow with the impacts of artificial influences removed. Artificial influences may include abstractions, discharges, transfers, augmentation and impoundments. National Climate Information Centre. NCIC area monthly rainfall totals are derived using the Met Office 5 km gridded dataset, which uses rain gauge observations. The process of increasing the water stored in the saturated zone of an aquifer. Expressed in depth of water (mm). The total capacity of a reservoir. The reservoir capacity normally usable for storage to meet established reservoir operating requirements. The difference between the amount of water actually in the soil and the amount of water that the soil can hold. Expressed in depth of water (mm).
Artesian Artesian Borehole Effective rainfall Flood Alert/Flood warning
Groundwater Long Term Average (LTA)
MORECS
Naturalised Flow NCIC Recharge Reservoir gross capacity Reservoir live capacity Soil moisture deficit (SMD)
Categories for rainfall, river flows, groundwater levels Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low
Value likely to fall within this band 5% of the time Value likely to fall within this band 8% of the time Value likely to fall within this band 15% of the time Value likely to fall within this band 44% of the time Value likely to fall within this band 15% of the time Value likely to fall within this band 8% of the time Value likely to fall within this band 5% of the time
Units mAOD mBTWL
Metres Above Ordnance Datum (mean sea level at Newlyn Cornwall). meters Below Top Water Level
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15
