1995 Drought Report A report on the severity of the drought of 1995 and its effect in the Severn and Trent catchments

For Internal Distribution Only

Water Resources Section Midlands Region M E kfORANDUM A g e n c y

The Environment Agency To: See Distribution List Overleaf Midlands Region Sapphire East From: Rachel Spence, Assistant Hydrologist 550 Streetsbrook Road Water Resources Solihull West Midlands Our Ref: 32/815/3550 B91 IQT Yonr Ref: Tel ; 0121 711 2324 Date: 25 July 1996 Fax : 0121 711 5824 Telex : 336748

1995 DROUGHT REPORT - Severn and Trent Catchments

This report details the effects of the 1995 drought on the Severn and Trent catchments. It concentrates . on a hydrological analysis of the drought and the principal Water Resource activities and problems. Effects of the drought on water quality and fisheries are also briefly covered.

A supplementary report will follow, when staff resources allow, detailing the post-drought conclusions and recommendations. This could include a summary of the actions that are being taken (or should be considered) to improve the management of a future drought, and a precis of the environmental effects of the Drought Orders in place during 1995/1996.

NOTE THAT THIS REPORT IS FOR INTERNAL DISTRIBUTION ONLY A cut down version for external distribution may also follow.

I hope that you will find this report a useful reference. If you have any comments or queries, please contact Gordon Davies (ext 3040 at Sapphire), or myself. I will be based in the SE Area of Welsh Region (St Mellons, Cardiff) for 6 months as of 1 st August.

RACHEL SPENCE Assistant Hydrologist Sapphire East, Midlands Region

Extension GTN 722 3220 Distribution:

Water Resources Staff

Sapphire : Andy Wood Regional Water Manager Steve Morley Regional Water Resources Manager Jim Waters Team Leader - Hydrometric Systems Dave Robinson Regional Licencing Officer Paul Crockett Senior Resources Engineer/Modeller Gordon Davies Team Leader - Policy and Planning Tim Harrison Team Leader_-.Operational -Hydrology ~ - " ------"Dickie Cross Hydrologist - Operational Hydrology Rachel Spence Asst. Hydrologist - Operational Hydrology Liz Mullis Asst. Hydrologist - Operational Hydrology Alison Williams Technical Asst. - Operational Hydrology Olton : Phil Stewart Senior Hydrogeologist Shrewsbury : Peter May Area Water Resources Manager Jean Payn Senior Water Resources Officer ' Jim Payne Hydrometric Officer Kidderminster : Mike Averill Asst. Hydrometric Officer Tewkesbury : Roger Wade Area Water Resources Manager Derek Taylor Senior Water Resources Officer Phil Davies Hydrometric Officer Warwick : Jerry Clewer Asst. Hydrometric Officer Fradley : Gwyn Williams * Area Water Resources Manager Anne Dacey Senior Water Resources Officer Tony Burrows Hydrometric Officer Trentside : Roger James Area Water Resources Manager Elfyn Parry Senior Water Resources Officer Simon Wills Hydrometric/Quality Instrumentation Officer Other Regions : Richard Streeter Bristol Headquarters Ian Barker Welsh Region Mike Eggboro North West Region John Mawdsley North East Region Wilson S Anglian Region Mike Owen - Thames Region Peter Herbertson Southern Region Terry Newman South West Region

Non-Water Resource Staff

Sapphire : Dave Grimshaw Team Leader - Hydrometric Data Phil Hickley Regional FRC&N Manager Wayne Baker Public Relations Olton Dave Foster Regional Scientist Dave Brewin Regional Water Quality Manager Shelley Howard Regional Biologist FOREWORD 1995 Drought Report

This report covers the principal activities, facts and figures relating to the 1995 drought in the Severn and Trent catchments.

A supplementary report may follow when staff resources allow, covering the following additional drought related topics :

Hydrological Features - temperature, evaporation and soil moisture - further detail on groundwater aspects Post Drought Order Assessment - summary of independent assessments o f the environmental effects of the 1995/96 Drought Orders Liaison and Planning During 1995/96 - liaison meetings between NRA/Agency and water companies - NRA/Agency and Water Company contingency plans - inter regional issues regarding water resources Lessons, Actions and Recommendations - problems encountered and lessons learnt - actions that are being taken or should be investigated to help alleviate future problems

M y 1996

1995 Drought Report Page i t Environment Agency - Midlands Region 1995 Drought Report - Phase I List of Contents Page Foreword i ' List of Contents ii List of Figures v

Chapter 1 : Introduction to the 1995 Drought Report

1.1 Aims of the Report 1 1.2 Structure of the Report. 1

Chapter'2~:-Overview-of-the-i995“Drought------

2.1 1995 Drought Summary 3 2.2 1995 Drought Diary 7

Chapter 3 : Hydrological Features

3.1 Rainfall Analysis 9 3.1.1 Introduction 9 3.1.2 Overview of 1995 Rainfall over the Severn and Trent Catchments 9 l 3.1.3 1995 Daily Rainfall Distribution 9 3.1.4 1995 Monthly Rainfall Distribution 12 3.1.5 Regional Variations. 12 3.1.6 Rainfall Return Period Analysis 18 3.1.7 Comparison With Previous Droughts 18

3.2 River Flow Analysis * 22 3.2.1 Introduction 22 3.2.2 Overview of 1995 River Flows in the Severn and Trent Catchments22 3.3.3 1995 River Flow Trends 23 3.2.4 Dry Weather Flow Analysis 26 3:2.5 Monthly Mean Flow Analysis 31

3.3 Groundwater 37 3.3.1 Overview of Groundwater Levels During 1995 37 3.3.2 Groundwater Hydrographs 37

Chapter 4 : Water Resources Management;

4.1 Introduction J 41 i i 4.2 River Severn Water Resource Management 42 4.2.1 Introduction to the River Severn Regulation System 42 4.2.2 Overview of the 1995 River Severn Regulation Season 42 4.2.3 Llyn Clywedog 43 4.2.4 Lake Vymwy 48 4.2.5 Shropshire Groundwater Scheme* 49 4.2.6 River Severn'Major Abstractions in 1995 50 4.2.7 Allocation of Regulation Releases 55

1995 Drought Report Page ii Environment Agency - Midlands Region Page 4.3 River Derwent Water Resource Management 57 4.3.1 Introduction to the River Derwent Water Resource Activities 57 4.3.2 Overview of the 1995 River Derwent Operations 58 4.3.3 Derwent Valley Reservoirs 60 4.3.4 Ogston & Carsington Reservoirs and Ambergate Abstractions and Releases 62 4.3.5 Little Eaton & Draycott Abstractions . - 66 4.3.6 Turbine and Sluice Operations 67

4.4 Tittesworth Reservoir and Leek Area Water Resources Management 70 4.4.1 Introduction to the Leek Conjunctive Use Scheme 70 4.4.2 Overview of the 1995 Tittesworth Operations 70

4.5 Other Water Resource Systems; 73 4.5.1 The River Leam System 73 4.5.2 The River Dove System 74 4.5.3 Chamwood Reservoirs 76 4.5.4 Blithfield Reservoir 76 4.5.5 Elan Valley Reservoirs 76 4.5.6 The River Blythe System 77

Chapter 5 : Other Water Resource Aspects

5.1 * Public Water Supply 79 5.1.1 Introduction 79 5.1.2 Overview of Public Water Supply Operations in 1995 79 5.1.3 Severn Trent Water Ltd. Supply Activities in 1995 81 5.1.4 South Staffordshire Water Ltd. Supply Activities in 1995 82 / 5.2 Spray Irrigation 83 5.2.1 Introduction 83 5.2.2 Overview of Spray Irrigation in 1995 83

5.3 Area Water Resource Activities, Events and Problems 86 5.3.1 Overview 86 5.3.2 Regionwide Issues 86 5.3.3 Upper, Severn Area 87 5.3.4 Lower Severn Area 88 5.3.5 Upper Trent Area 89 5.3.6 Lower Trent Area 89

1995 Drought Report Page iii Environment Agency - Midlands Region Page Chapter 6 : Other Impacts of the Drought

6.1 Introduction 91

6.2 Overview of Water Quality, Biology and Fisheries v 91

6.3 Water Quality # 94

6.4 Biological Quality 97 6.4.1 Upper Severn Area ' 97. 6.4. 2 Lower Severn Area 97 ~6A3 U pper' Tren t-Area------97 6.4.4 Lower Trent Area ~ “ ----- — ------98.

6.5 Fisheries 99 6.5.1 Impact of Low River Flows on Fisheries 99 6.5.2 Effect of the Drought 99 6.5.3 Storm Incidents , 101 6.5.4 Other Effects on Fisheries in 1995 101

6.6. River Tame Incident - July 1995 102

6.7 Other Environmental Effects of the Drought 10.4 - ' Chapter 7 : Further Information

7.1 Further Reading ^ 105 7.2 Acknowledgements 106

Appendices

Appendix 1 , Ordinary Drought Orders 1995 A1 Appendix 2 Description of the River Severn Regulation System A3 Appendix 3 River Severn Regulation 1995 - Diary of Significant Events A13 Appendix 4 Discussion of 1995 River Severn Regulation Efficiency A19 Appendix 5 River Derwent Operations 1995 - Diary of Significant Events A25 Appendix 6 River Derwent at Belper Pound A31 Appendix 7 Upper Severn Compensation Systems A35 A7.1 The Hadley Brook Compensation System ; A35 A7.2 The Strine Catchment Compensation System A35

1995 Drought Report Page iv Environment Agency - Midlands Region 1995 Drought Report - Phase I List of Figures

Page Chapter 2 : Overview of the 1995 Drought

2.1 Table : Minimum Reservoir Storages in Recent Drought Years 4

Chapter 3 : Hydrological Features

3.1 Graph : .1995 Daily Rainfall Hyetograms - Severn Basin 10 3.2 Graph : 1995 Daily Rainfall Hyetograms - Trent Basin 11 3.3 Table : 1995 Monthly Rainfall Distribution - Severn and Trent Sub-Regions 13 3.4 Graph : Monthly Rainfall and.Cumulative Deficits.- Severn Basin 14 3.5 Graph : Monthly Rainfall and Cumulative Deficits- Trent Basin 15 3.6 Map : Rainfall as % LTA - April to August 1995 and April to November 1995 16 3.7 Map : Rainfall as % LTA April 1995 to March 1996 17 (with raingauge and reservoir locations) 3.8 Table : 1995 Individual Raingauge Rainfall Return Periods and Rank 19 3.9 Table : 1995 Regionwide Rainfall Compared to Previous Drought Years 20 3.10 Graph : Cumulative Rainfall Deficit over the Severn Trent Region 21 (1995 Compared with 1989 and 1976) 3.11 Graph : 1995 Flow Hydrograph and Flow Duration Curve 24 for the River Tanat at Llanyblodwel 3.12 Graph : 1995 Flow Hydrograph and Flow Duration Curve 25 for the River Meese at Tibberton 3.13 Table : Severn Catchment Dry Weather Flows 28( 3.14 Table : Trent Catchment Dry Weather Flows 29 3.15 |Map : 1995 Dry Weather Flow Return Periods 30 3.16 Table : Analysis of Lowest Mean Flows Over Various Multi-Month Durations 33 (Severn and Trent Basins) 3.17 Map : Return Periods of Average Flows in 1995 : 1-Month and 8-Month Durations 36 3.18 Graph : Groundwater Level at Heathlanes 38 3.19 Graph : Groundwater Level at Anthony’s Cross 38 3.20 Graph : Groundwater Level at Four Crosses 39 3.21 Graph : Groundwater Level at Swinnow Wood 39

Chapter 4 : Water Resources Management

4.1 Table : Severn Regulation - A Comparison of Recent Droughts 43 4.2 Graph : River Severn Regulation Releases 1995 44 4.3 Graph : Llyn Clywedog Operations 1995 46 4.4 Graph : Lake Vymwy Operations 1995 47 4.5 Table : Shropshire Groundwater Scheme 49 (Historical Gross Abstraction Compared to Licensed Quantities) 4.6 Graph : Net Abstractions Upstream of Bewdley 52 4.7 Table : Major River Severn Abstractions 53 4.8 Graph : 1995 River Severn Gross and Net Abstractions 54 4.9 Pie Chart : Allocation of 1995 Severn Regulation Releases 56

1995 Drought Report Page v Environment Agency - Midlands Region Page

4.10 Table River Derwent Support and Abstractions by Severn Trent Water Ltd. 58 4.11 Graph : Derwent Valley Reservoirs Operations - May to December 1995 59 4.12 . Graph : Ogston Reservoir Operations - May to December 1995 63 4.13 Graph : Carsington Reservoir Operations - May to December 1995 64 4.14 Graph : Total River Abstractions and Reservoir Releases Upstream of Derby 65 4.15 Graph : Major River Abstractions Upstream of Derby • 68 4.16 Graph : Major River Abstractions Upstream of Church Wilne 69 4.17 Table Compensation Requirements of the Tittesworth and Leek System 71 4.18 Graph : Tittesworth Reservoir Operations - May to December 1995 72 4.19 Graph : The Dove Reservoirs Operations - May to December 1995 75

Chapter 5 : Other Aspects of Water Resources

5.1 Graph : Weekly Public Water Supply Demands and Temperature Variations 80 5.2 Table : Surface Water Spray Irrigation Licensed and Used Quantities 1995 83 5.3 Graph : Cumulative Restrictions on Surface Water Abstraction Licences 1995 84 5.4 Table : Licensed Abstraction Restrictions 1995 85

Chapter 6 : Other Impacts of the Drought

6.1 Table : River Severn and Major Tributaries 92 - Mean River Quality 1989 - 1995 6.2 Table : River Trent and Major Tributaries 93 - Mean River Quality 1989 - 1995 6.3 Graph : 1995 Dissolved Oxygen and Ammonia Concentrations 96 6.4 Graph : Reported Fish Mortality Incidents 1995 100 6.5 Graph : Dissolved Oxygen and Ammonia at Water Orton on the River Tame 103

Appendices

Appendix 1 : Ordinary Drought Orders 1995 A l.l Table : Summary of Ordinary Drought Orders 1995 A1

Appendix 2 : Description of the Severn Regulation System A2.1 Map : The River Severn Water Resources / Supply System A5 A2.2 Table : Hampton Loade and Trimpley - Details of Licence Conditions A8 A2.3 Table : Major Severn Public Water Supply Abstractors A10 - Summary of Licence Conditions

Appendix 4 : Discussion of 1995 River Severn Regulation Efficiency A4.1 Graph : Daily Analysis of River Severn Regulation Releases 1995 A23 A4.2 Graph : Monthly Distribution of 1995 Severn Regulation Additional Releases A24

Appendix 6 : River Derwent at Belper Pound A6.1 Graph : Effect of Belper Pound on Derby Flows A33

Appendix 7 : Upper Severn Compensation Systems A7.1 Table : Hadley Brook Compensation Requirements and 1995 Operations A35

1995 Drought Report Page vi Environment Agency - Midlands Region CHAPTER 1: INTRODUCTION TO THE 1995 DROUGHT REPORT

1.1 Aims of the Report : ' . _ \ V. This report documents the effects of the 1995 drought on the Severn and Trent catchments, concentrating on the hydrological and water resource aspects. It is a factual report on the ■ severity and the management of the 1995 drought, and includes contrasts with other recent droughts to put 1995 into context.

The report is intended to be used primarily by Water Resources staff in the Midlands Region ' of the Environment Agency, to serve as a record of the; natural hydrological event and the responsive actions taken by both the National Rivers Authority (the Environment Agency predecessors) and public water supply companies. It may then be used as a guide and reference in the next drought, as a training document for new staff, and as an information source for future water resource modelling exercises. The report js also available to other regions and the headquarters of the Environment Agency, to enable interregional contrasts in drought severity and responses. Note that this version of the report is for internal distribution only. -

Hydrometry and water resources are managed by the Environment Agency on a hydrological catchment basis, consequently, this report deals only with the Severn and Trent catchments. Similar information for other parts of the Midlands Region can be obtained from the Water Resources Departments of neighbouring regions.

1.2 Structure of the Report

The report is structured in a cascading-detail format. Chapter 2 is a complete standalone overview of the 1995 drought, including comparisons with recent droughts, and a 1995 diary of events and responses. Subsequent chapters include an overview at the start of each major . topic, followed by more detailed information.

'Chapter 3 covers the hydrological features of the drought. It documents the shortage of rainfall over the Severn and Trent catchments, with estimates of return periods. Rainfall is the only means by which the severity of a drought can be independently measured, since it is not influenced by man. The effect of the rainfall shortage on both short and long term river flows is also included, since low river flows and reservoir inflows influence the impact of a drought, particularly on public water supply and farmland irrigation abstractors. Groundwater aspects of the drought are very briefly covered.

Chapter 4 covers the effects of the drought on the water resource systems operating in the Severn and Trent catchments. Some brief background descriptions are included within the report for the benefit of readers unfamiliar with these systems, and a more detailed description of the Severn Regulation System is given in the Appendices. The River Severn resources management is given detailed attention, since the River Severn Regulation System is managed by Environment Agency Water Resources staff. The chapter also concentrates on the complex River Derwent water resource activities managed by Severn Trent Water Ltd, particularly since the new Carsington Reservoir proved so useful in its first operational drought year. Summary information on the other principal Severn and Trent catchment reservoirs and water resource systems is also included.

1995 Drought Report Page 1 Environment Agency - Midlands Region \

Chapter 5 deals with other water resource aspects. The public water supply demands of Severn Trent Water Ltd. and South Staffordshire Water Ltd. are summarised with a discussion of their activities and the difficulties faced. The spray Irrigation section includes estimates of agricultural spray irrigation demands over the region, with details of the restrictions imposed on licenced abstractions by the National Rivers Authority in 1995. The chapter also includes a summary of the water resource activities, events and problems in the four Areas.

Chapter 6 deals with non water resource aspects of the drought, and details the impact of the drought on water quality, biology and fisheries. Some attention is given to the catastrophic fish kills in the River Tame and downstream River Trent which resulted from summer thunderstorms in July 1995. Other environmental effects of the drought are briefly covered.

References to other reports related to the 1995 and previous droughts are given in Chapter 7.

1995 Drought Report Page 2 Environment Agency - Midlands Region CHAPTER 2: OVERVIEW OF THE 1995 DROUGHT

2.1 ' 1995 Drought Summary

2.1.1 Drought Classification The shortage of rainfall and accompanying high temperatures and soil moisture deficits produced a serious, long duration environmental drought. The prolonged nature of the hydrological shortages resulted in a moderate water supply drought.

2.1.2 Rain Tali following exceptionally high rainfall over the winter of 1994-95, the drier than average weather began in March. Regionwide rainfall totals were consistently below average from March to August, with rainfall in August only 1 1% average.

Five-month April to August rainfall totals were only 37% average, and were generally lower than comparable totals in the drought of 1975-76. The Soar basin, containing the Chamwood Group of reservoirs, was worst affected with rainfall at less than 30% average. Five-month rainfall return periods exceeded 100 years in much of the Trent basin where the rainfall deficits were greatest.

September rains brought some relief, but the drier than average weather returned for much of the winter period, resulting in a regionwide 12-month April 95 to March 96 rainfall total of just 67% average. The 12-month rainfall return period exceeded 100 years in the Trent headwaters, and was 60 years at Lake Vymwy. The prolonged nature of the rainfall deficits had severe impacts on impounding reservoir storages. The areas receiving the lowest percentage rainfall unfortunately coincided with the locations of the major supply reservoirs, with the Derwent Valley, Tittesworth, Vymwy and Blithfleld reservoirs all receiving below 60% of the average 12-month rainfall. Winter Drought Orders were necessary at the first three of these four locations.

2.1.3 River Flows Dry weather flows (minimum weekly flows) in 1995 were around two-thirds of average, but / generally higher than those experienced in the droughts of 1975-76 and 1989-91. Minimum monthly mean flows occurred during the exceptionally dry August, with the average monthly flow little more than the dry weather flow.

The prolonged nature of the drought produced long duration average flows that were rare compared to previous years. Eight-month flows were frequently lower than in 1975-76, and return periods exceeded 40 years at more than half the sites analyzed. These prolonged low flows .not only increased the rate of reservoir drawdown as resources were used faster than they could be replenished, they also hindered river abstractions for public, water supply, pumped refill of reservoirs and agricultural irrigation. The unusually long duration of the low flows, rather than the magnitude, caused the greatest problems for abstractors.

2.1.4 Groundwater The drought of 1995 was preceded by several wetter years, and groundwater levels were generally near average for the time of year at the start of the summer of 1995. The rainfall deficit that began in the Spring continued over the Autumn and Winter period, delaying the saturation of soils and thus severely restricting winter recharge. At the end of the 1995/1996 recharge season, groundwater levels were mostly below average.

1995 Drought Report Page J Environment Agency - Midlands Region /yyi

ruh Report Drought Will .support,enabled the storage at Clywedog to remain above the ’Seek Drought Order’ control control Order’ Drought ’Seek the above remain to Clywedog at storage the .support,enabled June to early November, at rates occasionally exceeding 200 Ml/d. In addition, raw water from water raw addition, In Ml/d. 200 exceeding occasionally rates at November, early to June l o h Ltl Etn upd btatos N or some of abstractions. place in point pumped abstraction Draycott Eaton Little downstream the the of flows of use all Low 1995. in days 4to frequent Reservoir just Carsington at refill prompted also pumped restricted Derwent the inOgston storage toconserve works treatment Ogston to transferred frequently was Carsington avoiding~the‘ thus Ml/d, 500 above rise to having releases Clywedog prevented and curve, upt rm hss ad I f h Srphr Gonwtr cee aon 8 M/ net) Ml/d 85 season, (around the Scheme throughout met be to Bewdley at Groundwater Severn River the Shropshire on the flow of II maintained and the I enabled Phases from output euain ol impose. would regulation - eevi rw dw fr aneac purposes maintenance for down drawn reservoir - m corc tt : - aifcoy C Cuig ocr , O DogtOdr n Forcc in Order Drought - DO , Conccrn Causing - C , Satisfactory - S : State Rcsourcc eevi ad vroe ae ult polm ascae wt agl los Lw lw in flows Low blooms. algal with associated problems quality water overcome and Reservoir maximum of state this that abstractions Severn River major the on limitations further tl asn ocr a ms fte eins eevisa h sato h 19 Srn season. Spring 1996 the were of start the at which reservoirs storages both region’s average the than lowerof hindered period, in most Winter at resulting and concern reservoirs, Autumn of the causing refill still over rainfall pumped low and natural Continued reservoirs. some iue . Mnmm eevi Soae i Rcn Dogt Years Drought Recent in Storages Reservoir Minimum 2.1 Figure Regulation - Reg , Supply - S Pumped - P , : Use Natural - NResource : Method Refill lw t eb adspotdwsra asrcin eemd lotcniuul rm mid from continuously almost weremade Carsington abstractions new the downstream by prescribed the maintain helped support to River and Derwent the to considerably Derby at Carsington were flow from Releases operations resources. resource Reservoir water Derwent River full The 1976. in September mid to days 121 and 1989 in October mid to days 125 with in spite o f upstream abstraction demands some 13% higher than in 1989. The groundwater groundwater The 1989. in than higher 13% some demands abstraction upstream f o spite in hn hs rahd n h 18-91 ruh, n wr lwr hn h 17-96 iia at minima 1975-1976 the than lower were and drought, lower 1989-1991 mostly were the storages in Minimum years. reached drought those previous in than and 1995 in reached storages River Severn Regulation took place for 124 days from mid June to early November, compared compared November, to early June mid from 124 days for place took Regulation Severn River minimum the tabulates 2.1 Figure drought. 1995 the of start the was at catchments state Trent and in Severn the reservoirs all satisfactory in a storage the in winter, wet the Following tr corc ytms ' - - • - • ' ’ s System Rcsourcc ater W Clywedog Tittcsworth Carsington Ogston Vyrnwy Charnwood ln Valley Elan Draycote ewn Vle 20.2 Valley Derwent Dove Blitti field R ROUP G OR RESERVOIR RESERVOIR 1995 40.5 32.5 29.7 38.6 55.5 28.2 43.1 35.2 14.5 17.8 MINIMUM STORAGE STORAGE MINIMUM s rs Capacity Gross % as 1989 1991 47m 41 38 029 30 49 23 30 22 69 52 to - - - 1984 n/a 41 n/a 40 46 45 33 ae 4 Page 52 51 1975 1976 / •78.6 • n/a / 85.2 n/a n/a 57. , DO C, 73.1 87.2 35 22 579.5 45 097.6 30 28 26 070.3 30 to 82.4 60.7 72.1 Resource State State Resource 73.0 niomn Aec - dad Region idlands M - Agency Environment RECOVERY RECOVERY at 1st April April 1st at % Full and and Full % 1996 , DO C, , DO C, . DO C. C C C S S S S Method (N (+Reg) S P(+N) N(+P) (N Reg P(+N) N(+P) Refill Reg N N N N N S N P I Resource (+Reg) S S Reg + Use S • s S S . s 2.1.6 Public Water Supply and Hosepipe Bans The long spells of hot, dry weather produced record demands for water in July 1995, with Severn Trent Water Ltd’s highest weekly demand reaching 2552 Ml/d, som e 2 I % above their annual forecast. No major supply interruptions were experienced in the Severn and Trent catchments, but some short-lived, localised problems did occur during the peak demand periods. These were generally due to treatment and distribution limitations rather than a lack of raw water supplies at this early stage in the season.

Media appeals for water conservation began at the end of June, but, following the privatisation of the water industry in .1989, the public were not as responsive to these appeals as they had been in the 1976 drought. Consequently, demands remained high until Severn Trent Water Ltd imposed a regionwide hosepipe ban on 22nd August. The hosepipe ban immediately reduced demands by around 5%. This was followed by cooler wetter weather in September, bringing demands back to normal. The ban was lifted over most of the region in January 1996, but remained in force until April 1996 in the East Midlands and Stoke supply districts. South Staffordshire Water Ltd did not impose a hosepipe ban, although the Severn Trent Water Ltd ban would also have encouraged South Staffordshire Water Ltd customers to reduce their consumption.

As the drought continued, Severn Trent Water Ltd followed a strategy o f conserving their rapidly depleting reservoir resources and maximising groundwater and river abstractions. The, improved flexibility of their treatment and distribution systems enabled supply demands to be met while direct reservoir abstraction works were rested. This strategy minimised the water supply impacts of the serious hydrological drought.

2.1.7 Drought O rders No Drought Orders were necessary during the height of the summer drought, however, as the dry weather continued, four drought orders were approved in the Severn and Trent catchments to assist reservoir refill and safeguard supplies for 1996. All of these Drought Orders ran. through the 1995-96 winter and spring period rather than the more environmentally sensitive summer and autumn seasons.

Drought Orders reducing reservoir compensation releases were granted for Tittesw'orth Reservoir (Severn Trent Water Ltd, 29/12/95-29/06/96),' the Derwent Valley Reservoirs (Severn Trent Water Ltd, 19/01/96-18/04/96) and Lake Vyrnwy (North West Water Ltd, 16/03/96-15/06/96). The Drought Order on the River Derwent at Ambergate (Severn Trent Water Ltd, 19/01/96-18/04/96) allowed a reduction in the licence flow' threshold, facilitating increased abstractions to enhance the rate of refill of Carsington and Ogston Reservoirs. There were no National Rivers Authority Drought Order applications in the Severn and Trent catchments.

2.1.8 Spray Irrigation Average regionwide spray irrigation abstractions over the early summer period were around 300 Ml/d, probably peaking at over 400 Ml/d towards the end of June. Less than 40% of annual licenced quantities were actually used, however. This was partly due to the restrictions imposed by the National Rivers Authority as river flows fell, in accordance with licence conditions. The number of restrictions imposed peaked in late August, when 80% of the Severn and 65% of the Trent licences that were subject to a flow-related restriction condition had been prevented from abstracting. Restrictions were also imposed on some licences applicable to the winter season only.

1995 Drought Report Page 5 Environment Agency - Midlands Region 2.1.9 Water Quality and Biology ' The drought had both positive and negative effects on water quality and biology. The rainfall deficit reduced the number o f pollution incidents arising from urban runoff, storm water overflows and farm silage liquors. Higher temperatures also increased the rate of in river self purification. However, the prolonged low river flows limited the dilution of sewage and industrial effluents, and reduced submerged habitats. Consequently, improvements in chemical and biological quality were seen at some sites, while deteriorations were observed elsewhere!

The main effect of the drought on water quality was a reduction in dissolved oxygen concentrations and an increase in ammonia. Overall, however, there were no serious adverse effects of the drought on water quality in 1995. The water quality in 1995 was generally better than in the 1989 drought, partly due to recent effluent treatment improvements.

The enhanced nutrient, temperature and light levels during the drought, combined with slow “ current velocities and windless conditions, caused-prolific growth of plant, phytoplanktonand. algal growth (particularly bluegreen algae and diatoms). The lower flows reduced effluent dilution and caused a loss of submerged habitats, leading to a general decline in the numbers and diversity of invertebrates. Many watercourses dried out in 1995 and established flora and fauna were subject to the encroachment o f other species. With recolonisation, however, long term effects are expected to be limited.

2.1.10 Fisheries The low levels and flows and hot summertime temperatures depleted oxygen concentrations. This caused much distress to fish, and frequent fish rescue operations were carried out. There were, however, many fish suffocations in both still and flowing waters. Fortunately, preliminary observations indicate that the low flows have not seriously affected spawning.

The most devastating fish mortalities were due to deoxygenation following the heavy thunderstorms in. July. The River Tame and downstream River Trent were worst affected when, after six weeks o f dry weather, the storms flushed all the accumulated pollutants from the Birmingham conurbation into the watercourses. Fish life was almost totally obliterated in . stretches o f the Tame, and around 20,000 fish died in the River Trent, although the NRA’s efforts to pump liquid oxygen into the River Trent undoubtedly saved many more. An extensive restocking programme followed, with over 100,000 fish introduced to the River Tame and River Trent during October and November 1995.

1995 Drought Report Rage 6 Environment Agency - Midlands Region 2.2 1995 Drought Diary

Previous Winter Heavy winter rainfall enabled refill of the region’s naturally filling reservoirs, such that all reservoir storages in the Severn and Trent catchments were in a satisfactory state at the start of the Spring period. Soil moistures were at field capacity for a prolonged period over the Winter, and frequent rainfall events produced ideal conditions for groundwater recharge. Groundwater levels had recovered to around or just below long term average, levels by the Spring.

Spring - Warm weather during May provoked significant rises in public water supply demands, mainly due to increased horticultural uses. April and May were both dry, and river flows and reservoir storages began to fall. With increasing river abstractions and falling natural flows, the River Severn Regulation Alert was issued on;5th,May....

June June rainfall was only 23% average regionwide, continuing the drier than average trend that began in mid March. River flows continued to fall, and River Severn regulation releases from Llyn Clywedog began on 17th June to support abstractions and maintain environmentally acceptable flows. Similar regulation releases from Carsington Reservoir to the River Derwent also began mid month. Abstractions from the River Dove at Egginton for the Dove Reservoirs were restricted as river flow fell. The first spray irrigation abstraction restrictions were, imposed in the River Tern catchment mid month on licences with conditions relating to prescribed river flows. Public water supply demands rose in line with rising temperatures, and public appeals to conserve water were made through the media, particularly focusing on the use of garden sprinklers.

July Record demands were experienced by Severn Trent Water Ltd at the end of June and start of July, with their average weekly demand peaking at 2552 Ml/d. South Staffordshire Water Ltd’s demands also peaked at 423 Ml/d at this time. These unprecedented demands resulted in some short term, localised supply disruptions.

After a long dry period, heavy thunderstorms mid month washed accumulated pollutants into the rivers, causing dissolved oxygen concentrations to plummet. This resulted in massive fish 'mortalities in many parts of the region, and the fish life in parts of the River Tame draining the Birmingham conurbation was virtually obliterated. As the polluted waters drained into the River Trent, a liquid oxygen unit was employed to aerate the water at Drakelow to ease the suffering of the fish.

River flows soon receded after the storms, and Phase II of the Shropshire Groundwater Scheme was required'to support River Severn Regulation. Regulation releases commenced from Draycote Water to the River Leam to support the downstream public water supply abstraction.

August August was exceptionally dry, with regional rainfall only 11% average. Soil moisture deficits were at their highest by the end of August, ranging from 75 to 156mm and reaching a regionwide average of 123mm.

1995 Drought Report Page 7 Environment Agency - Midlands Region As natural river flows continued to fall; Phase I of the Shropshire Groundwater Scheme (in addition to Phase II) was required to support River Severn Regulation. Low flows on the River Derwent prompted Severn Trent Water Ltd to substitute Little Eaton abstractions with poorer quality water from Draycott downstream in order to meet their demands and maintain the required river flows. Abstraction restrictions in accordance with flow-related licence conditions reached a peak in August, with restrictions applied to 80% of those licences subject to'such conditions in the Severn Basin, and 65% in the Trent.

Severn Trent Water Ltd imposed a regionwide hosepipe ban on 22nd August. This brought about an immediate reduction in demands of some 5 to 6%, but was followed by a period of cooler, wetter weather, returning demands to normal levels.

September and October A wet SeptemberbrougKt~some'reIief with-rainfain37%-average.-This,was,the_first_month since Februaryiwith rainfalhabove; average>regionwide. As river flows rose, the abstraction licence restrictions gradually began to be lifted.

Reservoir storages reached a minimum during September at Llyn Clywedog (41%) and the Elan Valley Reservoirs (33%). Lowest storages occurred at Ogston Reservoir (28%) and Blithfield Reservoir (35%) in October, but reservoir drawdown continued elsewhere.

Releases from Lake Vymwy were made during two high spring tide periods to increase flows in the lower reaches of the River Severn and prevent saline waters in the estuary intruding upstream to a major abstraction point. These additional releases used up over 20% of the remaining Vymwy Water Bank resources. Maintenance work at Llyn Clywedog required low reservoir levels and forced the release of resources during a wet period which would otherwise have enabled a storage recovery of 2.5%.

' November River Severn Regulation ended on 11 th November after 124 Regulation Days in 5 periods. The Regulation Alert was called off on 23rd, 203 days after it was declared. Carsington Reservoir releases to the Derwent ceased early in November, and limited pumped refill of Ogston and Draycote Reservoirs began. Reservoir storages reached a minimum during November at Lake Vymwy (30%), Draycote Water (56%), Tittesworth (15%), and the Dove (43%) and Chamwood (18%) reservoir groups, but continued to fall at Carsington and the Derwent Valley Reservoirs.

Following Winter Autumn and Winter rainfall was also low, with 6-month totals from October 1995 to March 1996 only 79% average. Soil moisture deficits, normally eliminated by the end of November, reached a minimum at the end of March 1996. beforesstarting to rise again. Minimum deficits over the region ranged from zero to 16mm, averaging 4mm. These prolonged soil moisture deficits severely reduced winter groundwater recharge potential.

After the prolonged period of low rainfall and high demands, reservoir storages were severely drawn down with low chances of refilling before Spring 1996 at some sites. Winter and Spring Drought Orders were sought to protect supplies in 1996. A 6-month Tittesworth Reservoir Drought Order was in force from the end of December, and 3-month Drought Orders for the Derwent Valley Reservoirs and the Ambergate abstraction (affecting refill of Ogston and Carsington reservoirs) followed in mid January 1996. A 3-month Lake Vymwy Drought Order came into force in mid March. Reservoir storages were still causing concern at some of the region’s reservoirs by April 1996.

1995 Drought Report Page 8 Environment Agency - Midlands Region CHAPTER 3 : HYDROLOGICAL FEATURES * * 3.1 Rainfall Analysis

3.1.1 Introduction

Shortage of rainfall is the obvious cause of a drought, and, being free of man’s influence, is the only independent measure of the severity of a drought Short .period shortage of rainfall can cause temporary river flow and supply problems, but it is often longer period deficits that1 have the greatest impact on water resources, particularly affecting reservoir refill rates and - groundwater recharge.

3.1.2 Overview of 1995 Rainfall over tlie Severn and Trent Catchments .

The 1995 drought was preceded by high* winter rainfall, producing considerable groundwater recharge and refilling the region’s reservoirs. Thus, the potential impacts of the summer rainfall shortage were reduced. . .

The 5-month lowest rainfall period in the 1995 drought from April to August was drier than the recent droughts of 75-76 and 89-91. The Soar basin, containing the Chamwood Reservoirs, was worst affected in this period. ;

The 1995 drought was more prolonged than recent drought, extending from April to mid November. It was followed by a dry Autumn and Winter, giving 12-month rainfall totals from April 95 to March 96 only 67% Long Term Average. (LTA) as a regionwide average. The regional variation of the longer duration rainfall shows a North^South trend, with the upland reservoired catchments worst affected. The three naturally filling reservoirs that were subject to Drought Orders (Vymwy, Tittesworth and Derwent Valley) are located in the region of greatest 12-month deficits with rainfall less than 60% average. The shortage of rainfall has hindered winter refill, leading to below average storage volumes at some reservoirs at the beginning the 1996 season.

3.1.3 1995 Daily Rainfall Distribution

The 1995 drought was characterised by regionwide prolonged diy periods, separated by heavy - thunderstorms or more persistent frontal rain. Typically, the rainfall on the highest 20 individual days accounted for 65% of the total rain in the critical April to November period, and 75%* of the days were dry (<1 mm). : .

There were 6 main dry spells between April and November where daily rainfall totals were continuously less than 1mm for two weeks or-more. The longest dry period extended for 5 weeks from mid July to late. August throughout most of the'region except the Welsh mountains. The period from early June to early July was also dry for. between 3 weeks and 5 weeks regionwide.

The distribution of daily rainfall totals in 1995 for representative stations throughout the region, including the Lake Vymwy and Derwent Valley Reservoir sites, is shown in Figures 3.1 and 3.2.

1995 Drought Report Page 9 Environment Agency - Midlands Region Dally Rainfall mm Daily Rainfall mm Daily Rainfall mm f Dally Rainfall mm 25 20 15 Figure 3.1 : 1995 Daily Rainfall Hyetograms - Severn BasinSevern - Hyetograms DailyRainfall 1995 : 3.1 Figure 5 d * * * * f ^ ^ ^ - - f-lflfifjP^jf * * * * * * * * * * * * * * * * * * * * * *********** * * * * * * * * * * f f * ^ * * * * * f j L da L i i Leamington□ (451663) Cetna (458427) Cheltenham □ I I JkJi --- j T j 1 juju Iflapii 4^^ tffl nf^i njflw Daily Rainfall mm Daily Rainfall m m ' i u e . :95 Daily Rainfall Hyetdgrarns Basin Trent :1995 - Figure 3.2 3.1.4 1995 Monthly Rainfall Distribution

The monthly areal rainfall data is tabulated on Figure 3.3 ift both mm and % LTA. Figures 3.4 and 3.5 graphically show the monthly rainfall data as a % LTA for the Severn and Trent basins respectively. The cumulative monthly rainfall deficits from April 1994 for 11 sub- regions are also shown. The start date has been selected to reflect the antecedent conditions.

The winter rainfall over the 1994/1995 season was significantly greater than average, with exceptionally high rainfall regionwide during December, January and February. The 3 .month total was 164% average for this period. This assisted groundwater recharge and reservoir refill suchthat resources were generally in a healthy state before the start o f the 199S drought*

Rainfall in March was slightly less than average, and marked the start o f a 6-month period of continuously below average rainfall. The 3-month period from June to August was exceptionally.^dry with rainfall-only 26% average.^ .

A wet September brought some relief with higher than average rainfall in all areas except the Welsh mountains. However, it was followed by a dry autumn and winter period. Rainfall over the 6 month period from October 95 to March 96 was only 70% average in the upland catchments, seriously hindering reservoir refill and groundwater recharge.

3.1.5 Regional Variations

Figures 3.6 and 3.7 show the regional variations in rainfall expressed as a % LTA for the driest 5 month (April to August), 8 month (April to November) and 12 month (April to. March)'periods. The locations o f the Jong term rain gauges and principal reservoirs are also shown.

The spring and summer rainfall for the driest five month April to August period showed a distinct East-West divide. Most of the Trent basin and the Avon catchment received less than 40% of average rainfall, whereas the rest of the Severn basin and the Trent headwaters received above 40% LTA. Totals were above 50% average in only a few scattered areas. The Soar basin (containing the Chamwood Reservoirs) and parts of Staffordshire and Derbyshire were worst affected, with less than 30% average rainfall.

Rainfall over the 8-month critical period from April to November showed a marked North- South graduation over the region. Virtually all of the Trent Basin and the Welsh mountains and North Shropshire districts received less than 60% average rainfall. The principal resource , reservoirs fall within this area. Rainfall as a proportion of average was higher over the Teme and Avon catchments, and increased towards the Severn Estuary, but only rarely exceeded 80% LTA.

The twelve month rainfall from April 1995 to March 1996 represents the 1995 drought and the following winter season. The regional variation displayed a similar graduation to the 8- month duration, from less than 60% LTA in the North'to above 80% LTA in the South. The Derwent Valley, Tittesworth, Vymwy and Blithfield naturally filling reservoirs are located in the worst affected areas. *

On the cumulative monthly rainfall deficit diagram^ (Figures 3.4 and 3.5), all parts of the .region display similar rapid rates of decline from the start of the 1995 drought, but the upland catchments show a continued steep decline through the following autumn and winter months.

1995 Drought Report Page 12 Environment Agency - Midlands Region Figure 3.3 :1995 Monthly Rainfall Distribution - Severn and Trent Sub-Regions

Sub^areal Monthly Rainfall in mm

Severn Severn ' Welsh Shropshire MU Sev Avon to Lower Sev Trent Upper Tame Dove Derwent Soar Lower Date Trent Basin Mountains Rain /Teme Evesham / Estuary Basin Trent Trent Jan-95 124 127 235 105 127 92 111 120 124 106 179 182 100 86 Feb-95 64 93 • 213 76 64 61 71 74 81 69 100 111 60 54 Mar-95 49 51 100 40 50 44 32 47 61 44 .66 71 39 30 Apr-95 20 21 31 19 20 19 21 18 1B 1B 23 29 14 15 May-95 46 64 68 49 48 57 54 39 41 35 ■ 51 47 . 34 40 Jun-95 13 13 18 14 12 12 2 14 14 • 14 15 20 11 12 Jut-95 30 39 69 33 46 15 31 21 25 17 38 39' 13 9 Aug-95 9 7 9 6 . 7 5 7 10 15 10 19 11 7 7 Sep-95 92 94 67 . 86 64 96 116 89 87 100 67 97 109 6B Oct-95 • 37 42 69 28 41 30 56 32 ‘ 35 32 45 42 26 22 Nov-95 60 66 90 41 69 59 ,74 .54 42 50 62 67 61 56 Deo-95 72 77 96 68 78 74. 73 67 66 70 74 80 71 62 Jan-96 40 45 .62 29 55 35 45 34 32 33 42 49 33 28 Feb-96 61 64 128 50 67 48 46 S7 64 47 80 85 52 50 Mar-96 38 46 79 43 55 24 46 29 31 26 37 46 25 23 I 1995 Annua) Total 636 684 1103 669 664 564 646 ' 585 601 565 759 ■ 796 545 461 5 months : Apr 9S - Aug 95 118 134 213 121 133 108 115 102 113 94 146 146 79 83 8 months: Apr 95 - Nov 95 307 336 459 278 327 293 361 277 277. 276 340 352 275 229 6 months: Oct 95 - Mar 96 308 340 . 524 259 363 270 340 273 262 258 340 369 268 241 12 months: Apr 95 - Mar 96 518 566 624 468 580 474 571 464 — 462 452 573 612 456 392

- Sub-areal Monthly Rainfall as % LTA (1941-1970). -

Severn Severn Welsh Shropshire Mid Sev Avon to Lower Sev ■ Trent Upper' Tame Dove Derwent •• Soar Lower Date Trent 8asfn Mountains Plain /Teme Evesham / Estuary Basin Trent Trent 1 Jan-95 180 1?4 169 169 187 159 1B2 182 185 174 in 186 169 162 Feb-95 158 166 201 163 156 139 148 148 159 144 152 142 128 120 Mar-95 94 94 111 82 64 96 74 94 102 68 106 103 63 70 Apr-95 38 • 40 36 40 38 42 46 35 ■35 37 37 43 30 36 May-95 72 79 72 73 70 97 93 65 65 56 73 64 61 60 Jun-95 23 r 23 21 26 22 24 4 25 25 27 21. 29 22 26 Jul-95 46 60 98 51 74 26 64 32 37 27 47 49 22 17 Aug-95 11 8 8 / 8 e . 7 9 13 19 13 20 12 • 10 11 Sep-95 137 • 132 74 * 135 122 168 190 144 128 - 169 105 113 196 ' 136 Oct-95 57 61 55 46 63 53 ‘ 98 52 ' 65 54 57 61 46 46 Nov-95 78 80 64 55 90 89 95 73 57 70 .07 ' 64 92 68 Deo-95 103 101 65 113 109 130 104 106 99 111 83 82 125 127 Jan-98 58 62 45 47 61 60 74 52 48 54 49 50 56 53 Feb-96 115 114 121 104 126 109 96 114 106 98 121. 109 111 in Mar-96 73 85 88 88 104 52 107 58 62 52 61 67 53 53

1995 Annual Total 82 85 83 78 86 64 . 92 79 79 79 81 80 81 76

5 months: Apr 85 - Aug 95 37 41 46 39 . 42 38 40 33 35- 31 '3 8 38 28 32 8 months: Apr 95 - Nov 95 56 61 54 54 62 63 74 55 53 56 54 54 60 55 6 months: Oct 95 - Mar 96 ' 79 83 70 73 94 82 95 75 70 73 72 70 61 ' 80 12 months : Apr 95 - Mar 96 67 70 62 64 75 71 81 63 ~,<61. 83 81 . 61 68 64 Cumulative Rainfall Deficit From April 94 (mm) Monthly Rainfall as % LTA ro i I 300 CO ro o O o o o O o Cumulative Monthly : Deficits Rainfall and Basin 3.4 Severn -Figure o o o o O

Apr/94 May/94 Jun/94 Jul/94 Aug/94 Sep/94 Oct/94 Nov/94 Dec/94 Jan/95 Feb/95 Mar/95 Apr/95 May/95 Jun/95 Jul/95 Aug/95 Sep/95 Oct/95 Nov/95 Dec/95 Jan/96 Feb/96 Mar/96 Cumulative Rainfall Deficit From April 94 (mm) Monthly Rainfall as % LTA

200 -*>-*> ro ro cn o oi o* cn o o o o o o Figure : Monthly 3.5 Rainfall Basin Deficits Cumulative Trent - and Apr/94 • Apr/94 May/94 May/94 Jun/94 Juri/94 Jul/94 Jjut/94 Aug/94 Aug/94 Sep/94 Sep/94 Oct/94 Nov/94 Oct/94 Dec/94 Nov/94 Jan/95 Dec/94 Feb/95 Jan/95 Mar/95 Apr/95 Feb/95 May/95 Mar/95 Jun/95 . Apr/95 Jul/95 May/95 Aug/95 Sep/95 Jun/95 Oct/95 Jul/95 Nov/95 Aug/95 Dec/95 Jan/96 Sep/95 Feb/96 Oct/95 Mar/96 Nov/?5 Dec/95 □ Jan/96 CO (D ! □ - § o ; o Feb/96 0) : < 3 CD : (D Mar/96 IS Z3 (D Figure 3.6 : Rainfall as a Percentage of 41-70 .ong Term Average: Showing Return Period Estimates at Long Record Raingauge Sites

5 -M onths April to August 1995 8-Months April to November 1995 Figure 3.7 : Rainfall as a Percentage of 41-70 Long Term .Average Showing Return Period Estimates at Long Record Raingauge Sites

t 12—Months April 1995 to March 1996 Location Map of Raingauges and Reservoirs 3.1.6 Rainfall Return Period Analysis

Continuous, long duration records are required to assess rainfall return periods, so the analysis here has been limited to just 9 locations where monthly records are available from 1908 to present The analysis has been carried out for three durations selected as the most significant in the 1995. drought : 5-months ^ ending between June ancl November, 8-months. ending between August and November, and any 12-mohth period. The variable end month for each duration avoids the misleading high return periods that would be obtained using fixed end points. Both linear-normal and log?normal distributions were tested^ but the linear option’gave- the best statistical fit.

The results are tabulated on Figure 3.8, and the return periods are also shown on the %LTA ______rainfall maps (Figures 3.6 and 3.7). As would be expected, the regional variations in the return period reflect the variations in the rainfall as a percentage LTA!

High return periods'were obtained for the'5-month duration analysis. In the Upper Trent, Tame and Soar areas, where the April to August 1995 rainfall was ranked first or second in the 88 year record, return periods are estimated at greater than 1 in 100 years. The raingauges nearest the Vymwy and Derwent reservoirs had less spectacular return periods of 1 in 35 and 1 in 26 years respectively. O f the nine sites, the lowest 5-month return period was 1 in 13 years at Worcester.

Although the 8-month April to November period was significant for water supply operations, it produced ' unremarkable. return periods, wh ich were generally the lowest of the three durations analyzed. , <

The 12-month analysis produced high return period estimates for the upland gauges. At Stoke.; on Trent; where the ApriI 95 to March 96 rainfalI was thelowestl2-inonthrainfalIon record^ - the return period was over 1 in .100.years. A t Lake Vymwy, it; was the second lowest 12- month rainfall on record with a return period of 1 in 60 years. However, in the Teme catchment and~LowerSevenrreaches,~Tainfalkwas much closer to average;and.return’periods' were as low as 1 in 2 years.

3.1.7 Comparison With Previous Droughts

Figure 3.9 compares the 1995 regionwide rainfall with previous recent drought years. The 95 drought critical period was from April to November, compared to April to August in 1976 and 1984, and inid April to mid October in 1989.

The 1995 5-month summer rainfall deficit was more severe than in other recent droughts, including 1976. Jlowever^ the high', antecedent rainfall before the 1995 drought helped to prevent a recurrence of the severe low river flow and water supply problems experienced in 1976. The operational flexibility of the regional water supply systems also helped to reduce the impacts of the drought on customers. For both the 8 month and 12 month durations, however, the 1975-76 drought was more severe in terms of rainfall deficits, but 1995 was considerably drier than 1989-91.

Figure 3.10 shows the cumulative regionwide rainfall deficits for recent droughts over a twenty four month comparable period. Obviously, the chosen start date has a significant influence on the end of period resultant deficit, so the 1995 data has been plotted from both April 94 and April 95. Hie diagram illustrates the close similarity between the 75-76 rainfall and the 95-96 deficits to March 1996.

1995 Drought Report Page 18 Environment Agency - Midlands Region 5 MONTH DURATION (ending between June and November)

1995 RANK for period 1908 to 1996 Return , RAINGAUGE 95-96 , 89-91 84-85 75-76 Year of. Period Top Rank Vymwy 35 3 5 1 2 1984 Hatton Grange 31 2 13 35 4 1938 Oakly Park 17 7 12 8 5 . 1938 DiglLs 13 10 40 15 4 1921 Hewletts 24 4 58 19 5 1938 Chatsworth 26 5 16 8 _ 2 1921 Meir >100 2 13 14 7 1959 Whitacre >100 : i - 1. 24 - 23 8 1995 Nanpantan >100 ' 1 . 39 25 3 1995

8 MONTH DURATION (ending between August and December)

, 1995 RANK for period 1908 to 1996 Return Year of: ' RAINGAUGEv. 95-96 89-91 84-85 75-76- . Period Top Rank Vymwy '24 4 14 3 5 . 1915 Hatton Grange 18 6 19 ^ - 34 2 1911 - Oakly Park 9 11 18 19 2 :192U Diglis . 9 11 38 14 4 v Hewletts 4 23 49 25 2 1929 Chatsworth ■ 30 ' 4 32 30 5 1921 Meir 95 2 28 . 18 .5 - 1911 Whitacre 27 3 38 > 44 4 ' 1929 Nanpantan 34 4 60 43 1 \ • . 1976

12 MONTH DURATION (ending any month)

1995 RANK for period 1908 to 1996 Return Year of RAINGAUGE 95-96 89-91 75-76 „ Period 84-85 Top Rank Vymwy 60 2 34 10 - 4 1933/34. Hatton Grange 18 4 6 60 1 1975/76 Oakly Park 4 21 8 48 1 1975/76 Diglis 4‘ 25 15 48 2 1963/64 Hewletts 2 48 6 65 1 1975/76 Chatsworth 30 5 14 18 2 1920/21 Meir >100 1 11 38 x2 1995/96 Whitacre 34 5 13 51 1 1975/76 Nanpantan . 45 3 15 41 1 , 1975/76

Figure 3.8 : 1995 Individual Raingauge Rainfall Return Periods and Rank .

1995 Drought Report Page 19 Environment Agency - Midlands Region DROUGHT Minimum Regionwide Rainfall as % LTA Over Given Duration YEARS 5-Month Duration 8-Month duration 12rMonth Duration 1995-1996 37.1% Apr-Aug 95 58.0% Apr-Nov 95 67.0% Apr 95-Mar 96 1989-1991 55.4% Mar-Jul 90 673% Mar-Oct 90 75.3% Mar 90-Feb 91 1984-1985 62.6% Apr-Aug 84 83.7% Jan-Sep 84 86.3% Apr 84-Mar 85 , • 1975-1976 44.3% Apr-Aug 76 54.1% Jan-Aug 76 58.9% Sep 75-Aug 76

' Figure 3.9 : 1995 Regionwide Rainfall Compared to Previous Drought Years

/995 Drought Report Page 20 Environment Agency - Midlands Region Cumulative Deficit from 1941-1970 LTA (mm) Figure : Cumulative3.10 Rainfall Deficit over theSevern TrentRegion A JL E NV A MR MAY MAR JAN NOV SEP JUL MAY 1995compared 1989with 1976 and 24Month Period JUL E NOV SEP JAN MAR 75/76/77 89/90/91 94/95/96 95/96 3.2 River Flow Analysis

3.2.1 Introduction

Whilst shortage of rainfall may be the obvious cause of a drought, the effects of the drought on river flows and reservoir inflows is of more concern to the Environment Agency; River flows will be influenced not only by the recent rainfall deficit, but also by temperature, soil moisture deficits, antecedent hydrological conditions and human interference in terms of abstractions, impoundments and discharges. _

: During hot, dry periods when flows are at their lowest, abstraction demands for agricultural use or.public water supply are generally at their highest River abstractions may be limited by ” 'licence conditions designed to maintain an environmentally acceptable flow, and reservoir abstractions may have to be reduced to conserve resources for later in the season. This inverse relationship betw^en resource^availability andtabstractiomdemands increases the impact of a drought on both the public and ihe water industry. In addition to the water resource problems, low river flows may also cause water quality problems, particularly through insufficient dilution of sewage effluent Low river levels and flows lead to increased water temperatures and reduced dissolved oxygen levels causing distress to fish. Low levels can also create navigation problems. v.

3.2.2 _ Overview of 1995 River Flows In the Severn and Trent Catchments i * The regional distribution 1 of low "flow return * periods f, reflected the pattern < o f summertime rainfall deficits in 1995. The effects, of the. rainfall deficit were abated in groundwater supported rivers by the healthy , state of the groundwater storage at the start of the summer, but river flows were nonetheless significantly limited due tojreduced soil throughflow and storm runoff components. ^

The short term minimum flows achieved are measured by the Dry Weather Flow (DWF) statistic.' In 1995, ?the DWF was generally about - two-thirds -r of the mean DWF, .with . a regionwide average return period of 8 years, ranging from 2 to 30 years. Minimum flows were lower than those in the 1984 drought but generally not as low as those in the droughts of 1975/76 and 1989/90/91. DWFs suffered most in the Soar basin, reflecting the most severe April to August rainfall deficits here. The exceptionally dry August, following five previous drier than average months, produced mean August flows only slightly greater than the DWF, with return periods generally higher.

The 1995 drought was exceptionally prolonged, and the mean flows over longer durations were rare in comparison with previous years. The 8-month duration flows were frequently lower than the 1975/76 comparabIe;average s; with estimated return periods 40 years or more at half of the gauging stations analyzed. Long duration low reservoir inflows were particularly significant at the Derwent Valley Reservoirs (8-month return period oyer 1 in 100 years) and Lake Vymwy (10-month return period 1 in 80 years), where Drought Orders were necessary to improve refill rates to protect supplies for 1996.

1995 Drought Report Page 22 Environment Agency - Midlands Region 3.23 1995 River Flow Trends

To give an indication of the overall pattern of flows during 1995, two sites have been selected: Llanyhlodwel on the River Tanat in the Welsh uplands, and Tibberton on the River Meese in the groundwater supported Tern catchment These two sites suffered similar percentage rainfall deficits in 1995. Hydrographs and flow duration'curves; highlighting .1995, are shown on Figures 3.11 and 3.12'. Long term monthly.mean flows and lowest daily flows on record are also included for comparison! - .

These figures illustrate that the effect of the summer rainfall deficit was abated by the healthy groundwater storage in 1995. Flows were maintained significantly above the lowest on record in the Meese, but approached the lowest flows measured in the upland catchment with little storage. A comparison of the 95-percentile flows at the two sites shows that the 1995 low flows were much closer to the long term average Jow flows in the groundwater, supported catchment The d955 9S-percentileiflow.'wasraiDundi80% average in the-Tern catchment, but only 50% average in the Welsh mountains:......

River flow hydrographs for Bewdley, Derby, Church Wilne and Marston are included elsewhere in this report. The Hydrometric Yearbook 1995, produced by the Hydrometric Data Team includes further examples of hydrographs and flow duration curves, together with a full listing of current meter gaugings carried out in 1995.

1995 Drought Report Page 23 Environment Agency - Midlands Region

Figure 3.12 : 1995 Flows atTibberton

A uth.: 2040 Name: TIBBERTON L o cat RIVER MEESE Period of Record (PoR) : 1974 to 1995 (22 complete years ueed)

■* ' / I (

Auth.: 2040 Name: TIBBERTON L o c a t.: RIVER MEESE Period of Analysis : 1974 to 1995 ( 22 complete years used)

X of time given value equelled or exceeded 3.2.4 Dry Weather Flow Analysis

3.2.4.1 Introduction and Overview x

The Dry Weather Flow (DWF) is a useful measure of the lowest sustained flows reached, and can be likened to the driest week in an average summer. The annual series of the lowest 7-day mean flow in each year are averaged to give the long term DWF. The 7-day duration evens out daily fluctuations in river flows caused by man’s influence, particularly weekend variations in t quantities abstracted and effluent. returned. The DWF reflects . the importance of groundwater support in maintaining summer river flows, however, it is strongly influenced by man’s activities such that comparisons with previous years are only meaningful where abstractions, impoundments and discharges have remained approximately constant

Figures 3.13 and 3.14 tabulate the 1995 diy weather flows at a selection of long-record gauging station^. infthe7SievenifandvTrent;catchments^Gomparisons with previous droughts in 198^9-1991, 1984 and 1975-I976 are included. Estimates of DWF return periods have been determined from plots of the annual DWF series, using both ’by-eye* curves and the fitted Gumbel EV1II distribution. These are mapped on Figure 3.1 S. To examine the hydrological severity of the drought, only gauging stations with relatively natural flow regimes have been examined. \ , V The DWF in 1995 was generally about two-thirds of the long term average DWF. Since the late 1950’s, the-lowest DWF’s were suffered in the 1975-1976 drought at nearly all the j selected sites, closely followed by the 1989-1991 drought DWF’s .in 1995 were generally higher than in these two droughts, but lower than during the drought of 1984.

O f the sites analyzed with records long enough to determine return periods, .the regionwide average DWF return period was 8 years. Over 60%'of the gauging stations selected had DWFs~ with return periods of more than 5 years; nearly 20% of the return periods were over 10 years.

3.2.4.2 Regional Variations

The effect of the rainfall drought was pronounced in .the Welsh mountain streams since they have little catchment storage to maintain flows in dry weather. Here, DWFs approached the - 1976 values and return periods were above 10 years. The Roden catchment, having less groundwater support than manyShropshire Plain rivers, was similarly affected with a return period of 17 years. On other Shropshire Plain rivers, the healthy groundwater storage maintained baseflows throughout the summer, but the pro longed hot, dry weather and high soil moisture deficits minimised soil throughflow to rivers. Resulting return periods were between 3 arid 8 years. -

In the mid-Severn and Teme basins, and in the upper reaches o f the Avon catchment, return periods were around the regionwide average of 8 years. DWFs in the middle and lower Avon and smaller lower Severn tributaries were close to average reflecting the lower rainfall deficits in these areas.

1995 Drought Report Page 26 Environment Agency - Midlands Region Oyer the Trent M>asin, DWFs were most severe in the Soar catchments, reflecting the significant 5-month rainfall shortage in this area. The .DWF was only a third of average on the Rothley Brook, lower than the 1976 flow, but this is probably due to the closure of sewage treatment works in the catchment On the Wreake the DWF was half of average with a return period of 18 years. At Drakelow on the Trent, the DWF was lower than in the 1989-91 drought with a return period of 17 years, representing the combined effect o f the Upper Trent and the Tame, catchments. In the Dove catchment, the DWF was most severe in the upper reaches, particularly in the Manifold tributary with less groundwater support than the Dove proper, with an estimated return period of 10 years.

DWFs were average on the River Amber (Derwent tributary) and on the River Anker. (Tame tributary). The DWF in the River Trent' at Colwick was 80% average with a return period of 8 years, representing the combined effect of the majority of the Trent basin subcatchments.

1995 Drought Report Page 27 Environment Agency - Midlands Region Figure 3.13 Severn Catchment Dry Weather Flows

* 'i , Site Year , ' .< ■ 1995 Period No; of : m i S4 of Return (** adjusted for of Years Top River Shropshire Period Record tfsed Mean' jfiWF Rank p m Rank DWff Rank D\VF Rank Rink , .‘JwJV.V.V.V.V.V.V.V.V.’iV. Groundwater) J -.V Dulas Rhos-y-Pentref 70-95 26 5.5 o.8 r; 2 OS 3 1.3 0.7 i 76 12 Tanat Llanyblodwel 74-95 20 47.5 ' T6.0 2 22.6 3 n/a n/a 13.0 1 76 12 ^ . r Perry Yeaton * 64-95 32 40.3 34.5 10 27.7 ’ 2 28.3 : ^ 4 14.7 1 76 3 i Rea Bk Hookagate 63-95 31 ‘ 21.9 16.8 6 15.0 3 n/a n/a 7.4 1 76 5 Tern Eaton 73-95 23 . 63.5 46.1; . 3' 503 6 48’l ■ '^ 5 . 34.4 1 76 8 Roden Rodington 62-95 34 40.6 20.1; •• 2 20 2 3 24.4 17.6 1 76 « 17

Tern Walcot * 61-95 ' 35 217 155 5 129 3 149 4 89 1 76 8 Worfe Burcote 70-95 26 , 32.5 2l!6: 6 13.5 2 27.1 10 5.1 1 76 5 Stour Kidderminster 54-95 42 123 89 4 98 7 115 21 . 54 1 76 7 Salwarpe Harford Hill 62-95 25 40.9 26.4 2 n/a n/a n/a n/a 153 1 76 9 Teme Tenbury 57-95 39 169 90 5 85 4 110 8 57 1 76 8 Avon Stareton 63-95 33 40.2 31.6 4 25.9 2 26.2 ' 3 16.5 1 76 7 Arrow Broom 58-95 34 75.0 62.7 10 54.7 5 n/a n/a 18.3 i 75 4 Avon Evesham 63-95 33 379 351 - 12 337 9 340 10 • 158 1 76 3 Isboume Hinton 73-95 22 7.9. 4.1 4 4.0 3 3.9 2 n/a' 1* 76 6 Leadon Wedderbum Bridge 63-95 3J: 27.9 21.5 7 19.1 4 n/a n/a | 6.0 1 76 5 Frome Ebley Mill 70-95 26 78.1 613, 6 50.8 3 70.8 12 , 23.4 1 76 5

> Figure 3.14 Trent Catchment Dry Weather Flows

' ■f ' 1 C V* DRY WEATHER FLOW ' S 'a - % ■ v ‘ Year Period No. of h-":9S' v > 89-91 ' 84 ■ 75-76 ‘ of 1995 : : x £ ;•;»:* £ : v ; :i: v :•: v :■: y v y y; top Return ; of . Years s River , v, / Site Rank period Record >Used ' ■ Meatt,o '.•i•jrm '• 'i- ’NfRank ✓ DWF Rank DWF. Bank DWF Rank rit. -■ Sow Gt Bridgford 72-95 21 31.6 21.9 4 20.5 2 n/a n/a 10.8 1 '76 6 Rea Calthorpe Park 68-95 28 22.5 18.6 4 15.5 I 18.7 ■ 5 16.9 2 91 7 Tame Lea Marston 82-95 14 661 649 5 578 . 1 592 . 7 2 n/a n/a 90 ' n/a Anker ' Polesworth 68-95 25 60.0 613 16 483 5 n/a n/a 22.7 1 76 2 Trent Drakelow 67-95 29 1289 952 2 1132 5 1059 ■ 4 669 1 76 17 Chumet Basford Bridge 75-95 17 45.6 • . 32.5 5 27.6 1 n/a n/a 35.9 7 91 5 Manifold Ilam 69-95 27 60.7 36.5 : 3 •' 35.2 2 413 ■1 28.4 1 76 10 Dove Izaak Walton ' 70-95 26 55.0 ' M i 4 34.0 2 40.3 '6 26.1 1 76 7 Dove Rocester 54-95 42 169'. : 132' ii 127 8 129 9 91 i 59 4 ■ Dove Marston 66-95 30 , 323 \ 244 6 220 3 235 * 5 150 1 76 5 - ’> - Amber Wingfield Park .72-95 24 32.1 V 32.1 : 10 26.7 ..3 293 8 : 16-9. 1 76 2 Wreake Syston 68-95 26 30.4 ■ 1'5?2: 2 292 11 26.0 7 8.6 1 76 18

Rothley Bk Rothley 74-95 19 13.1. 4?4 • ' I :: 8.5 ■ .3 n/a n/a 53 2 ?5 - . n/a Trent Colwick 59-95 37 2544 : 2020 , 5 ’ 1869 3 2160 8 1338 1 76 8. Tome Auckley 72-95 24 30.6 '■20 A 4 20.1 3 31.4 13 15.6 1, . 76 9. <3 3.2.5 Monthly Mean Flow Analysis

3.2.5.1 Introduction and Overview

Whilst the dry weather flow analysis reflects the severity of the drought in terms of m inim um flows reached, it does not reflect the severity in terms of the duration of the low flows; Short­ lived low flows may cause short-lived quality or environmental problems, but prolonged low - flow spells result in low reservoir inflows and restricted river abstractions, caus mg the greatest water'supply difficulties.

Figure 3.16 tabulates the 1995 mean flows over various multi-month durations at a selection of long record gauging, stations in the Severn and Trent catchments.. Comparisons with previous droughts in 1989-1991, 1984 and 1975/1976 are included. Only long record sites have been used, to give meaningful comparisons. The flows have been naturalised at Clywedog,. Vymwy^andttheriDenvent^Valleyj^reseEvoirs. .to represent' reservoir - inflows: A t: - Bewdley,.Marston and Derby, flows have also'been naturalised by removing the effects of upstream river regulation, reservoirs and major abstractions and effluent returns to indicate the natural severity of the drought Similarly, the flows at Walcot and Yeaton have been adjusted to remove the effects of the Shropshire Groundwater Scheme borehole pumping. Estimates of . flow return periods have been determined by fitting log-normal and linear-normal distributions. The log-normal distribution generally gave a better fit to the observed data. The analysis of the flow data has deliberately been confined to calendar years, forcing the multi-month mean, flows to centre around the summer period, thus preventing double counting of, non-« independent events. ^

Generally, the short and the long multi-month durations gave higher return periods than the middle durations. The 1-month and 8-month return period estimates are mapped on Figure " 3.17. ‘ ‘ . • ' v.- • ■

The exceptionally dry August resulted in 1-month mean flows only slightly greater than the dry weather flow; producing return periods generally higher than^those of the -DWF. 'The’ minimum monthly mean flows were generally higher than in 1976 but comparable with those of 1989-91 and lower than in the drought of 1984.

The 1995 drought was exceptionally prolonged, and the longer duration mean flows were rare in comparison with previous years. The 8-month duration flows were- frequently lower, than ■ the 1975-76 comparable averages, with estimated return periods 40 years* or more at half of - the gauging stations analyzed. The long duration low reservoir inflows were particularly significant at the Derwent Valley and Vymwy Reservoirs. The 8-month return period at the Derwent Valley Reservoirs was over 1 in 100 years, and the 10-month return period at Lake Vymwy was 1 4nj80‘ years. iThe continued?low .flows; enhanced the rate of drawdown and seriously hampered refill rates, necessitating winter Drought Orders to reduce compensation releases and improve refill prospects to protect supplies for 1996. i 3.2.5.2 Regional Variations

Short duration mean flows were unusually less notable than the middle durations in the Welsh Mountain reservoired catchments. Return periods increased, with increasing duration, peaking at 1 in 80 years at Vymwy (10-months) and 1 in 40 years at Clywedog (8-month). Return periods for all durations were notably-lower in*the groundwater-supported Perry and* Tem - catchments, since the groundwater resources had started the season in a healthy state.

1995 Drought Report Page 31 Environment Agency - Midlands Region In the Teme catchment and the combined Severn catchment to Bewdley, all durations had return periods over 10 years, peaking at 50 and 67 years respectively over the 8-month duration. The low natural flows at Bewdley required a prolonged River Severn Regulation season, ending in November. At Bewdley, the 1995 drought flows were lower than those of all previous recent droughts over the 8-month duration, with only 1933 being lower in the period of record. In the Avon catchment, however, rainfall deficits were much lower and at . Evesham on the lower reaches all durations had return periods below 10 years. Flows on the- * Avon were comparable with those in the 1984 drought, but significantly higher than during the 75-76 and 89-91 droughts. The relatively higher'^Avon flows combined*with the-upper- ■ * Severn flows to produce return periods on the Lower Severn at Haw Bridge lower than those at Bewdley.

In the Trent basin, the most striking feature was the exceptionallyhigh retum period of the"— Derwent Valley reservoir inflows at over 100 years for the 8-month duration. Inflows over this • ■*’ duration were ;the dowest^n >recordj(startirigil93P^(&iresponding with a "rainfall-deficit o f • over 40% average for the same period. A winter Drought Order was required to overcome the inflow shortage and protect supplies for 1996. The long duration flows downstream on the River Derwent at Derby were similarly affected, with 8-month flows having a return period of 50 years. These low natural flows were supported w ith almost continuous releases from Carsington Reservoir throughout the summer to protect the public water supply abstractions dependent on the^ow at Derby.

Flows in the upper Trent and Tame catchments, represented at-Yoxall and Drakelow, were j second only to the 75/76 flows for all durations analyzed, with^exceptionally.: high - short - / duration return periods. At Co I wick, representing the combined effects of the majority of the . Trent basin, the 10-month duration was most significant with an estimated return period of 63 years. _ “

1995 Drought Report Page 32 Environment Agency - Midlands Region Table 3.16 : Analysis of Lowest Mean Flows Over Various Durations.- Severn and Trent Basins

1995 ' Rank " .1995 Flow Lowest flow Site and Dates'' Duration R eturn' ; on Record {Mouths) s Period 894H / 84 ; 75^76 " M l/d 1 Starts ■ +Ml/d- S ta r ts N * S' Month , Month

Llyn Clywedog - 1 3 24 28 14 1 25 7/95 4 8/76 Inflows 2 3 22 16 . 9 , 1 34 5/95 10; 7/76 ; 1933-1995 3 ' .4 16 7 3 2 .43 6/95 12 7/49 63 yts 4 7 . 7 5 2 3 43 5/95 20 6/49 5 ' 11 6 4 1 3 48 ' 4/95 23 4/84 ^ 6 19 5 6 1 2 52 4/95 31 3/84 8 40 2 24 8 3 68 4/95 64 ; 5/33 10 23. 3 31 23 4 99 3/95 80 3/33

Lake Vyrawy 1 12 8 25 • 6 1 24 8/95 u 8/76 Inflows 2 16 6 18 5 I 35 8/95 18 7/76 1933-1995 3 13 7 8 2 1 54 7/95 26 6/76 63 yrs 4 26 3 4 1 2 62 6/95 41 1 4/84, 5 26 5 3 1 2 78 5/95 46 4/84 6 67 3 6 1, 5 168 4/95 63 3/84 8 67 3 7 5 6 137 4/95 108 4/33 • 10 80 2 16 20 6 178 3/95 139 3/33

Yeaton / 1 4 . 8 3 4 1 36 , 8/95 18 7 • 8/76 River Peny 2 4 9 3 6 1 41 . 7/95 21 7/76 (adjusted SGW) 3 ' 4 . 8 3 6 42 8/95 .25 6/76 1964-1995 4 5 7 '• 3 . 6 1 43 7/79' . 31 5/75 32 yrs 5 7 7 3 6 1 44 7/95 , 3 6 7/76 . 6 * 9 5. 2 7 6 46 6/95.. ... 38 ..■■>.■6/64* • 8 ■' 14 " 4 2 7 . ■ '5 , 54 5/95 48 4/64 10. 8 6 3 13 4 - 79 3/95 63 1/92, Rodington 1 32 2 3 4 1 23 8/95 19 8/76 River Roden 2 15 2 3 5 1, 29 7/95 22 7/76 1962-1995 3 10 4 2 6 1 34 7/95 26 6/76 34 yrs 4 13 3 2 8 1 36 7/95 33 5/76 5 15 2 1 8 4 37 7/95 37 6/90 • - ' 6 17 2 6 3 ' ,40 6/95 40 5/90 8 26 2 1 6 3 52 5/95 51 4/90

. 10 14 4 12 2 81 3/95 76 3/90

Waicot 1 8 4 1 6 2 163 ' 8/95 80 7/91 River Tern 2 ■5 6 1 7 2 197 7/95 85 6/91 (adjusted SGW) 3 5 7 I 8 2 218 7/95 117 6/91 1961-1995 4 6 7 8 2 222 7/95 132 6/91 35 yrs . 5 7 7 8 3 229 7/95 148 6/91 6 9 • 6 1 8 4 234 . 6/95 168 5/91 8 12 5 1 7. 4 271 5/95 202 5/91 10 9 5 1 14 4 352 3/95 290 3/91

Bewdley 1 23 2 6 3 1 633 8/95 315 8/76 River Severn 2 11 6 5 2 1 870 8/95 398 8/95 Naturalised 3 12 7 3 6 1 1020 7/95 525 6/76 1922-1995 4 16 4 2 6 1 1089 6/95 772 5/76 74 yrs 5 22 4 2 7 1 1119 6/95 1019 4/76 6 39 2 4 8 1 1307 5/95 1301 4/76 8 . 67 2 8 12 7 1653 4/95 1548 5/33 10 23 6 9 35 5 2742 3/95 2408 1/64

Table Continued on Next Page... '1995 Rank 1995 Flow Lowest Flow Site and Bates D uration' Return on Record (Months) Period 95 89-91 84 75-76 jpi,;; Start Ml/d Start y s .:MontfaU Month

Tenbuiy 1 13 4 2 11 1 97 8/95 64 8/76 River Teme 2 11 5 2 11 112 8/95 f 76 7/76 1957-1995 . 3 15 4 2 10 119 . a®5 95 6/76 39 yrs 4 22 3 1 10 ' 129 7/95 125 6/90 5 27 2 ' N 1 10 148 6/95 136 6/90 6 32 . 2 1 9 . 3 . 183 5/95 153 5/90 . : 8 50 2 1 10 3 271 4/95 254 4/90 10 12 5 . 1 22 584 3/95 459 3/90 Stareton ' " 1 6 ------3 ------~ 2— — 4 _ 34 8/95 21 7/76 River Avon ‘2 - ‘ 2 0 -V ' 3 , .2 5 36 7/95“ ----- 2 6 - — 7/76- 1963-1995 , s 3;‘ * 10 ' 4 ' 2 ‘ : 5 1 42 6195 28 6/76 33 yrs 4 6 5 3 4 1 51 5/95- 31 : 5/76 5 7 5 3 6 53 6195 33 4/76 6 8 . 4 2 - 6 1 56 5/95 36 3/76 8 13 4 3 9 68 4/95 45 2/76 10 8 4 2 9 112 3/95 60 1/76 Evesham . • 1 5 6 7 9 364 8/95 195 7/76 River Avon 2 5 7 6 8 393 7/95 215 7/76 1963-1995 3 4 7 ■ '-5 - 9 439 6/95 235 :/ 6/76 33 yrs 4 4 8 . 5 7 488 7/95 257 ' 5/76 5 4 7 5v 6 497 6/95 111 4/76 6 5 7 5 6 1 528 6/95 300 3/76 . 8 7 5-- 4 9 613 4/95 347 1/76 10 4 7 2 11 937 3/95 444 . 1/76. Haw Bridge - 1 23 2 14 ‘ 3 1229 8/95 ,705 8/76 River Severn 2 11 5 9 3 1645 7/95 « 779 7/76 1933-1995 3 11 5 8 6 1 . 1872 6/95 999 6/76 ,63 yrs 4 12 7 6 10 2064 6/95. 1383 5/76 ' * 5 . 15 6 4 10 1 2250 6/95 1757 4/76 6 24 2 5 10 1 2441 5/95 2328 4/76 8 33 2 . 9 « 15 3 3069 4/95 4815 5/33 10 . 7 13 11 31 5 5230 3/95 3535 2/34 Yoxall 1 33 2 ' 3 9 1 316 8/95 214 8/76 River Trent 2 . 23 2 3 - 9 341 7/95 263 7/76 1960-1995 3 20 2 3 10 393 6/95 314 6/76 36 yrs / 4 18 2 3 9 1 421 7/95 350 5/76 5 24 2 3 9 1 435 7/95 365 4/76 6 27 2 3 7 1 445 6/95 400 3/76 8 33 2 4 6 513 4/95 435 1/76 10 18 2 4 - 14 1 650 2/95 560 1/76 Calthorpe Park 1 12 2 3 .10 1 23 8/95 22 7/76 River Rea 2 5 5 2 16 29 7/95 24 6/76 1968-1995 3 12 4 .2 14 1 30 6/95 27 5/76 28 yrs 4 10 3 2 8 1 32 5/95 29 4/76 5 17 3 2 7 1 33 4/95 31 4/76 6 17 3 1 | 9 2 34 4/95 32 4/90 - 8 44 1 2 ! 8 3 36 4/95 36 4/95 10 35 1 2 10 6 43 3/95 43 3/95

Table Continued on Next Page.. 1995 Rank 19^5 Flow . . Lowest .Flow Site and Dates Duration - Return .o n Record - (Months) Period 95 89-91' 84 75-76 Mi/d Ml/d ' S tart MontJT . M onth.

Drake low 1 55 2 7 9 I . 1015 8/95 934 8/76 River Trent ' 2 17 2 7 11 1205 7495 947 7/76 1967-1995 3 12 2 6 12 1 1363 8/95 1022 6/76 29 yrs 4 16 2 8 10 I 1371 7/95 1119,' 5/76 5 20 2 5 11 1 1404 7/95 1161 4/76 6 28 2 5 8 1 1474 6/95 1277. 3/76 8 40 2 5 7 1562 4/95 1462 ' ' 1/76 10 30 2 4 12 1905 3/95 1750 .1/76 Rocester 1. 6 8 7 11 2 .140 8/95 58. 9/59 River Dove 2 . . 7 . 8 7 9 2 146 8/95 83 9/59

1954-1995 3 10 * 7 5 .V ‘ 10; 2 149- 8/95 92 8/59 ‘42 yrs 4 11 4 5 9 2 161: 7/95 111 7/59 5 12 4 5 6 2 172 7/95 111 6/59 6 19 3 5 6 2 182 6/95 128 5/59 8 27 2 6 .7 3 227 5/95 186 3/59 10 15 4 6 9 2 336 - 3/95 215 2/59

Marston 1 4 17 11 3 ,0 6 258 8/95 116 9/49- River Dove 2 4 14 11 24 6 288 8/95 152 8/59

Naturalised 3 7 10 v 8 18 5 295 8/95 175 5 7/59- 1933-1995 4 8 9 8 16 : 4 309 , 7/95 - 198 6/59

63 yrs 5 11 7 8 15 . 4 331 7/95 218 6/59 6 19 4 6 14 3 350 6/95 271 5/59 8 3 2 2 7 13 3 433 5/95 369 2/34

10 16 5 8 ... 19 2 . .622 ,3/95 465 • 2/34;

J Derwent Valley 1 17 ' ' 4 \ 2 8 3 43 8/95 27 9/59 Reservoirs 2 8 '9 1 7 . 3 64 7/95 34 8/89 Inflows 3 12 7 9 4 77 6/95 49 8/47 1933-1995 4 13 8 6 9 86 7/95 62 7/47 63 yrs 5 26 4 7 8 90 6/95 76 6/59 6 50 3 4 10 6 96 5/95 85 5/59 8 . >100 1 4 12 5. 117 .5/95 117 5/95 48 2 .5 . 21 3 172 3/95 151 2/59 * 10 ; Derby 1 3 25 17 3 567 8/95 253 9/59

River Derwent 2 3 2 2 . 4 1 12 ' 3 574 : 8/95 -299 8/59 Naturalised 3 5 15 3 12 2 . 582 8/95 363 7/59 1933-1995 4 7 12 3 14 2 588 8/95 416 7/59 63 yrs 5 10 8 2 11 3 604 7/95 450 6/59 6 16 7 2 11 4 631 6/95 559 5/59 8 . 50 I 2 11 3 702 5/95 702 5/95 ' 10 28 3 5 17 1 940 3/95 921 3/76 Colwick 1 17 3 4 8 1 "2093 ' 8/95 1593 8/76 River Trent 2 11 4 3 10 1 2291 7/95 1637 . 7/76 1959-1995 3 9 5 3 10 1 2517 6/95 1802 6/76 37 yrs 4 11 5 3 11 1 2570 7/95 2049 5/76 5 13 5 3 10 1 2650 6/95 2247 4/76 6 18 5 3 8 1 2729 6/95 2389 4/76 8 28 3 2 8 3128 4/95 2841 2/76 10 63 3 4 13 1 4073 3/95 3445 2/76 Figure 3.17 : Return Periods of Average Flows in 1995 For 1 and 8 month durations 3.3 Groundwater

33.X ' Overview of Groundwater Levels During 1995

Heavy rainfall over the winter of 1994/1995 gave ideal conditions for aquifer recharge. Soil - moisture deficits were quickly eliminated and the frequent rainfall events ensured prolonged saturation of soils until early April 1995. Groundwater levels continued to rise until around June 1995 in most aquifers, and levels recovered to just below normal for the-time of year. The.effect of the rainfall deficit beginning in mid March began to show early in the summer, however, as groundwater levels fell and spring flows reduced. The deeper aquifers were less affected. ^

j As lower thajp average rainfall continued into the Autumn and Winter seasons, soil moisture deficits (normally eliminated in .November) remained throughout the winter in the Trent catchment and neighbouring parts of the Severn catchment- Deficits reached a minimum Regionwide average of 4mm at the end of March before starting to rise again. Consequently, there was little groundwater recharge over the winter 1995/1996 period. By May 1996, at the end of the normal recharge season, groundwater levels remained below average for the time of year in most aquifers.

3.3.2 Groundwater Hydrographs

Figures 3.18 to 3.21 show the change jn groundwater levels from 1973 onwards, to put the 1995 drought into context # ' } ■ - - ' . * The four representative hydrographs clearly show the effects o f the 1975-1976 and 1989-1991 droughts. Although there is an observed response to the 1995 drought, its effects are less dramatic as it was preceded by several wet years. Should the drought continue through 1996, the impact on groundwater will be more serious.

1995 Drought Report Page 37 Environment Agency - Midlands Region Tem catchment, 12km NW Telford

1973 1975 1977. 1979 1981 . 1983 1985 1987 1989 1991 1993 1995 1974 1976 1978 1980 1982 1984 1986 1988 1990 ’1992 1994 1996

Figure 3.19 Groundwater Level at Anthony's Cross 1 1 Sherwood Sandstones at SO 72002350 , Leadon catchment, 12km NW Gloucester U1 o * <0 A 00

& O) Ol da & & $ Groundwater Level (metres aod) Level Groundwater Groundwater Level (metresGroundwaterLevel site below datum)

1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 Groundwater Level (metres aod) Groundwater Level (metres aod) Wi 0> 00

Groundwater Level (metres below site datum) 1995 Drought Report Page 40 Environment Agency - Midlands Region CHAPTER 4 : WATER RESOURCES MANAGEMENT

4.1 Introduction

This chapter covers the 1995 activities of each of the principal reservoir and water resource systems in the Severn and Trent catchments.

The River Severn Regulation System is managed on a day to day basis by the-Environment Agency. South Staffordshire Water Ltd manage Blithfield Reservoir and the River Severn abstraction at Hampton Loade. All other surface water resource systems in the region are managed by Severn Trent Water Ltd.

The River Severn Regulation System is covered in detail since it is managed by the Environment Agency. The chapter also concentrates on the complex Derwent catchment activities, including Cars ingtomReservoirope rat ions-The Tittesworth Reservoir and Leek conjunctive use scheme is discussed in some detail, since it was subject to a Drought Order. The Welsh Region Elan Valley system is briefly covered as its raw water transfers to the Midlands Region impact on local supply strategies.

Overviews of the 1995 operations relating to the River Severn and River Derwent systems are included at the start of those sections. A complete overview of the'regional water resource, systems is included in Chapter 2.

!

1995 Drought Report Page 41 Environment Agency - Midlands Region 4.2 River Severn Water Resource Management

4.2.1 Introduction to the River Severn Regulation System

The aim of the River Severn Regulation System is to ensure that there is sufficient flow in the river to satisfy the demands of major abstractors on the Severn and to meet environmental needs. Available resources from Llyn Clywedog, Lake Vymwy and the Shropshire Groundwater Scheme are carefully released to maintain a minimum flow at Bewdley, situated half way along the length of the Severn, throughout the low flow season. The system is operated and managed under a Section 20 (Water Resources Act 1991) Operating Agreement.

A detailed description of the River Severn Regulation System is given in Appendix 2, ~ covering'the "three-resource-components,-the ^maintained, flow at Bewdley, and the major abstractors and their licence limitations.lt also details the tools and techniques used ~ by"tKe Operations Team at ^regional headquarters in:the.day to day management of the system. The sections below assume a background knowledge of the system and concentrate on details relating to the 1995 drought and comparisons with previous droughts.

4.2.2 Overview of the 1995 River Severn Regulation Season

The 1995 River Severn Regulation Season was notable for its extended duration from 17th June through to 11th November, spanning 148 days in total. There were 5 separate regulation periods, between which rainfall temporarily eliminated the need for additional releases, giving . a total of 124 regulation days. This compares with 125 days ending 18th October in 1989 and 121 days ending 15th September in 1976.

The full output from ^Phases I & II of the Shropshire Groundwater Scheme enabled the 850 Ml/d 5-day prescribed flow at Bewdley to be met throughout the Regulation Season without the need to release more than 500 Ml/d from Clywedog. Consequently, the additional restrictions on major abstractors that this maximum regulation state would impose were never in force. Abstraction demands within licence conditions were met throughout the season, , despite a 13% rise since 1989 in the volume of the major summertime abstractions upstream of Bewdley.

No Drought Orders were necessary during the 1995 River Severn Regulation Season, with the minimum Clywedog storage of 40.5% (24/09) remaining some 5.4% above the ’Seek Drought Order* control curve, thanks to the Shropshire Groundwater support. However, North West Water Ltd were granted a Drought Order at Lake Vymwy from mid-March to mid-June 1996, authorising a reduction in compensation to assist with refill to protect supplies for 1996.

The relative proportions of regulation support from the three sources, Llyn Clywedog, Lake Vymwy and Shropshire Groundwater, were 75%, 11% and 13% respectively, amounting to 42,400 Ml (excluding compensation releases and using the net groundwater output). Of these total releases above normal compensation, 47% were to support the major abstractors upstream of Bewdley, 23% were for environmental purposes, and 4% were for operational reasons.

Figure 4.1 tabulates the principal statistics relating to the operation of the Severn Regulation System in 1995, and includes comparisons wjth the drought years of 1989 and 1976. Figure 4.2 illustrates the lagged daily releases from each component and the maintained Bewdley 5- day flow. A diaiy of the significant Severn Regulation activities and events is included in Appendix 3, covering details of the rainfall, abstractions, flow recessions and resource considerations that prompted the 79 regulation release changes during the season.

1995 Drought Report Page 42 Environment Agency - Midlands Region Figure 4.1 : Severn Regulation - A Comparison of Recent Droughts

1995 1989 1976 SEVERN REGULATION SEASON Start and End Dates (not continuous) 17/06-11/11 30/05-18/10 18/05-15/09 No. of Regulation Days 124 125 - 121

SUPPORT SOURCES Total Volume Released in Regulation Season Ml 42400 48600 39000 (above compensation, net groundwater)

Percentage Allocation of Total Releases % Llyn Clywedog 75 75 100' Lake Vymwy. 11 18 0 Shropshire Groundwater Scheme (net) 13 7 ■ 0

Peak Regulation Releases Ml/d Llyn Clywedog 495 493 520 Lake Vymwy . 150 145 0 Shropshire Groundwater Scheme (net) 85 40 0

Minimum Reservoir Storage % ‘ * Llyn Clywedog 40.5 30 22 Lake Vymwy 29.7 38 35 ' K

MAJOR ABSTRACTIONS UPSTREAM OF BEWDLEY . 262 232 164 Average Summer Abstraction ' Ml/d (June- (June- ’ (June- (Shelton, Ironbridge, Hampton Loade, Trimpley) October) . October) September)

DROUGHT ORDERS 1995 : one Drought Order reducing Lake Vyrnwy compensation during the following spring. 1989 : one Drought Order restricting Llyn Clywedog regulation releases, to 2% of the remaining storage per day or to that required to 'meet the reduced (from 850) 730 Ml/d Bewdley maintained flow (whichever is the least). 1976 : first Drought Order allowing the 1-day Bewdley. maintained flow to reduce from 727 to 545 Ml/d, and lifting the Llyn Clywedog compensation requirement; second Drought Order restricting Llyn Clywedog regulation releases to 2% of the remaining storage per day or to that required to meet the reduced maintained flow (whichever is the least).

OTHER NOTES - Bewdley maintained flow : was 727 Ml/d as a 1-day mean in the 1’976 drought (now 850 Ml/d as a 5-day mean; 650 as a 1-day mean). > - Vymwy Water Bank : not available in the 1976 drought (although releases were made on 4 days per month for fisheries purposes). - Shropshire Groundwater Scheme : did not exist in the 1976 drought; only Phase 1 (net ~40 ML/d). was available in the 1989 drought; Phase 11 also available in 1995 (net ~45 Ml/d).

1995 Drought Report Page 43 Environment Agency - Midlands Region Figure 4.2: River Severn Regulation Releases 1995 showing Bewdley 5-day mean flow and lagged releases Flow Ml/d t ' Start Regulation 17/06/95 ETnd Regulation 11/11/95 20Q0

1500

1000 -

500 -----

0 l— August September October November

Clywedog Vymwy SGW .Bewdley Additional 3 day lag 2 day lag 2 day lag 5 day flow Releases 4.2.3 Llyn Clywedog

The changes in storage at Clywedog Reservoir throughout 1995 are shown on Figure 4.3, along with the total releases and overspills as measured at Bryntail just downstream of the dam. The diagram also illustrates the control curves relating to summer operations.

The high winter rainfall enabled the reservoir to start the 1995 spring season.at 97% full. When Severn regulation was first required on 17 June, Clywedog was selected as the first resource to be used, given its healthy storage.

The Maximum Regulation Alert was issued on 14th August, signifying the expected increase in Clywedog releases to 500 Ml/d, with all available Phases of the Shropshire Groundwater Scheme (SGWS) on full and Lake Vymwy releases at the maximum sustainable flow of 70 Ml/d. Releases peaked at 495 Ml/d for three days in late-August, however, and the Maximum Regulation State was not reached^^paring thev major abstractors on the Severn from the additional restrictions that this state would impose. The rate of fall in storage was over 5% per week for much of the period between mid-June and early September, and preparatory work on a Clywedog Drought Order began, but the Drought Order was not required. Storage reached a minimum of 40.5% on 24th September, 5.4% above the ’Seek Drought Order* control curve, compared with 30.1% in 1989 and 43% in 1976. Total volumes released from Clywedog above normal compensation during the 124 Regulation Days amounted to 30758 Ml, averaging 248 Ml/d.

Inspection and urgent maintenance work at Clywedog in October required steady low reservoir levels. The work took place following rainfall when river flows were naturally high in a non­ regulation period, and the high reservoir inflows were released in order to prevent the reservoir level rising. The total volume of additional releases over normal -regulation requirements for this period was 1238 Ml, which would have produced a welcome recovery in storage at Clywedog of approximately 2.5%.

At the end of the regulation period, Clywedog releases were returned to the minimum generation flow of around 45 Ml/d rather than the minimum compensation of 18.2 Ml/d. This enabled the generation of hydro-electric power for on-site use (rather than purchasing power from the grid), and was allowed because winter rainfall scenarios suggested only a slim chance of the reservoir not refilling by the next spring. Following a dry winter, however, releases were cut to the minimum compensation on 26th Januaiy 1996 to assist refill, and storage recovered to 87.2% by 1st April 1996. By the end of May 1996, the reservoir was virtually full and .hydropower releases were made to prevent spilling.

1995 Drought Report Page 45 Environment Agency - Midlands Region Figure 4.3 : Llyn Clywedog Operations 1995

Drought Order In Force

Seek Drought Order Figure 4.4: Lake Vymwy Operations 1995 4^ O O i—* i—* >■■* 4^ oo 4^ o o LO N> o LO K> O 4^ OO K> o o O o o o o N> o O Percentage Full ^LnO>i'*-JOOVOOi—* 4 o »—1 o o o t o l l . o Flow (M l/d) or Bank Volum e (M l) N ) U > o OO o V—k V—k 4^ -O O CD O O CD O O O O O O' O O O o

ct 0 - 16-Jul 02-Jul 15-Jan 30-Jul 01-Jan 18-Jun 29-Jan 12-Feb' 04-Jun 10-Sep 26-Feb 08 09-Apr 23-Apr 12-Mar 22-Oct 24-Sep 26-Mar 17-Dec 13-Aug 03-Dec 31-Dec 19-Nov 27-Aug 05-Nov 07-May 21-May 1995 4.2.4 Lake Vyrnwy

The changes in storage at Lake Vymwy and the Vymwy Bank balance throughout 1995 are shown on Figure 4.4,-along with the total releases and supply volumes.

The reservoir storage started the spring season at 98% full. Regulation support from Lake Vymwy was first required on 29th June, the 13th Regulation Day. The maximum release for regulation purposes was 150 Ml/d on 3rd October. Over the 1995 regulation season, a total volume of 4840 Ml above normal compensation was released.

North West Water Ltd’s direct abstraction from Vyrnwy Reservoir reduced from 23,5 Ml/d to 200 Ml/d towards the end of August when the Vymwy storage fell below 50% full, averaging ______212 Ml over the entire Regulation season.

At the end of the-season, only ;697 Ml-remained in ;thesVymwy bank, and Vyrnwy Reservoir reached its 1995. minimum storage of 29.7% on 11th November. This compares with a minimum storage of 38% in 1989 and 35% in 1976. Inflows over the regulation season were exceptionally low, with a return period of 1 in 80 years over the March to December period.

In addition to providing support to the Severn regulation system, water from the Vymwy Bank was also used during two spring high tide periods to prevent the saline water encroaching up the estuary as far as Gloucester; Low fluvial flows in the lower reaches of the Severn could allow saline water to reach the River Severn abstraction point for the Gloucester and; Sharpness canal. Bristol Water Pic abstract from this canal,for Bristol’s public water supply. The tidal support releases peaked at 267 Ml/d on 5th September, contributing a total volume (above normal regulation requirements) of 908 M l over the two periods, each using 20% of the remaining Vyrnwy Bank resources available. .

Following the dry winter and limited refill, North West Water Ltd were granted a Lake Vymwy Drought Order running from 16th March until 15th June 1996. The Drought Order assisted spring refill by reducing the downstream compensation releases from 45 to 25 Ml/d. This also reduced the potential gains to the Vymwy Water Bank. Full details of the Drought Order are given in Appendix 1.

By 1st April 1996 Lake Vymwy had only recovered to 73.1% full, compared with an average storage of 98% for the time of year. By 1st June 1996, the storage had risen to 85%. However, the Vymwy Water Bank balance stood at 3807 Ml on 1st April 1996, some 2350 Ml higher than normal since carry-over at the end of the summer season is usually eliminated by flood drawdown releases or overflows the following winter. Ironically, the 1995 drought produced above average Vymwy.Bank resources for the purposes of River Severn Regulation at the start of the 1996 season.

1995 Drought Report Page 48 Environment Agency - Midlands Region 4.2.5 Shropshire Groundwater Scheme

The operation of the Shropshire Groundwater Scheme in 1995 is detailed in a separate report prepared by the regional groundwater staff (see Chapter 6).

Phase I of the scheme was used operationally in 1989, but Phase II had only previously been used in tests during 1991 and 1992. Both Phases were necessary for River Severn Regulation support during the 1995 drought. _

When regulation began on 17th June, the storage at Clywedog was below the Shropshire Groundwater Scheme control curve. However, Clywedog was 95.7% full at this time, and the Vymwy bank balance stood at 2295 Ml. These resources would.be sufficient to maintain Severn Regulation support throughout an average summer without the need for expensive groundwater pumping, so the issue of the Shropshire Groundwater Scheme Phase Q Alert was delayed until 29th June.

Pumping from Phase II began on 1 Oth July, and the Phase I alert was issued at this time. The scheme was turned off after just a few days following unexpectedly heavy rainfall, but restarted at the end of July. Pumping from Phase 1 (in addition to Phase II) first commenced on 7th August Five of the six separate periods of groundwater support in 1995 required both Phases for all or part of the time. Groundwater support ended on 12th November (although the last official Regulation Day was the 11th), and the Shropshire Groundwater Scheme Alert; was cancelled on 17th November. The borehole support was operated on 89 days and. contributed 5617 Ml (net) or 13% of the total support to the Severn Regulation system: This represents 16% of the annual licensed quantity of the full scheme, or 42% and 56% of the Phase I and Phase Q yearly allowances, as tabulated in Figure 4.5.

There were no major operational difficulties relating to the Shropshire Groundwater Scheme in 1995, and no specific complaints were received from farmers or landowners attributing dried up wells or dry soils to the operation of the scheme.

Annual Volume Used in MI Vol Used in M l (As % Annual Licensed Quantity) (As % 5-Year Licensed Quantity) 1991 to 1989 1991 1992 1995 1995 1995

3678 0 0 2823 2823 2823 Phase I (55%). (0%) (0%) (42%) (19%) (19%) 0 2047 1629 3677 7353 3677 Phase II (0%) ' (31%) (25%) (56%) (52%) (26%) Total 3678 2047 1629 6500 10176 6500 Scheme (9%) (5%) (4%) (16%) (12%) (8%)

Figure 4.5 : Shropshire Groundwater Scheme - Historical Gross Abstraction Compared to Licensed Quantities

1995 Drought Report Page 49 Environment Agency - Midlands Region 4.2.6 River Severn Major Abstractions in 1995

Figure 4.6 shows the 1995 daily pattern of the net abstractions for the four principal sites upstream of Bewdley compared to the natural flow. Combined abstractions from these four sites averaged 262 Ml/d from June to October, but varied between 110 and 400 Ml/d. Comparable averages for 1989 and 1976 (June to September) were 232 and 164 Ml/d, respectively.

4.2.6.1 Shelton Although gross abstractions averaged 16 Ml/d from June to October, approximately three quarters of the water was returned through sewage works downstream, giving an average net abstraction of 4 Ml/d. The peak gross abstraction rate o f 25 Ml/d occurred in early August.

4.2.6.2 Ironbridge • " _ Cooling water abstractionrfor the power station'were-large but most of the water was returned ^ downstream and net abstractions averaged 17 Ml/d from June to October. The abstraction was significantly reduced at weekends. * 4.2.6.3 Hampton Loade This is the largest of the River Severn public water supply abstractions, and is operated by South Staffordshire Water Ltd (SSW). It accounted for 69% of the combined total abstraction from the 4 main sites upstream of Bewdley over the Regulation Season. The abstraction represented a net loss to the Severn above Bewdley. A new licence came into force in 1995 ? (see Appendix 2) which allowed daily abstractions up to 280 Ml (rather than the previous 220 Ml) when Bewdley flows were below 1100 Ml/d, provided Trimpley’s abstraction was no more than 120 Ml. The average abstraction over the June to October period was 184 Ml/d, peaking at 260 Ml/d on 4th July and 272 Ml/d on 29th October. Comparable averages for 1989 and 1976 (June to September) were 181 and 121 Ml/d.

In 1995, SSW tried to kepp their Chelmarsh bankside storage reservoir full to give maximum security of supplies in the event of a River Severn pollution incident. Pumping from the River Severn at Hampton Loade was greater overnight to take advantage of the cheaper electricity tariffs. The mean daily residual flow at Bewdley was heavily influenced by this abstraction.

The NRA were able to temporarily restrict the proposed abstraction at Hampton Loade in order to protect the maintained Bewdley flow if the regulation release requirements had been underestimated. However, any abstraction restriction would result in the drawdown of Chelmarsh storage as SSW continued to use the resources for supply. When the abstraction restriction was lifted, SSW would have to refill the reservoir at less favourable electricity rates, thus, the NRA agreed to compensate SSW according to the volume of the restriction imposed.

Hampton Loade abstraction restrictions were required on a total of 7 days during August and November when natural flow recessions were faster than expected and releases had not been increased early enough. The maximum 9am drawdown at Chelmarsh reservoir resulting from these restrictions was 342 Ml (11%). Total compensation payments in 1995 amounted to £2400. - - -

1995 Drought Report Page 50 Environment Agency - Midlands Region 4.2.6.4 Trimpley This public water supply abstraction represented 24% of the combined total abstraction from _ the 4 main sites upstream of Bewdley over the regulation season. TTie average abstraction over the June to October period was 61 Ml/d, peaking at 142 Ml/d on 12th July. This was much higher than in previous drought years, with comparable averages for 1989 and 1976 (June to September) of 30 and 18 Ml/d. The abstraction represents a net loss to the Severn above Bewdley.

The abstraction rates were highest early in the season when up to 20 Ml/d of raw water was being transferred.to Frankley Treatment works to support supplies for Birmingham when Elan Valley Aqueduct transfers had been reduced to conserve the Elan Valley Reservoirs storage. A further 40 Ml/d treatment capacity and associated treated water strategic pipeline from Trimpiey works was available from June 1995, and additional abstractions took place to provide supplies for North Worcester (to replace the Barbourne* treatment works further downstream). ‘

The Trimpley abstraction licence contains a 100 Regulation Days clause, limiting abstractions to an average 60 Ml/d over the Regulation Days (see Appendix 2). High abstraction rates averaging 70 Ml/d over the first 70 Regulation Days had to be drastically cut later in the summer to 37 Ml/d to keep within the 100-Regulation Days licence limitations. Abstractions rose to around 110 Ml/d during the. temporary breaks in regulation, and averaged 58 Ml/d during the Regulation Days after Day 100.

4.2.6.5 Spray Irrigation ’ - There were around 360 surface water spray irrigation licences upstream of Bewdley in 1995. About a third of these could be restricted when river flows fell below a prescribed flow. Since most of the water is lost by evapotranspiration, spray irrigation abstractions represent a net loss to the catchment flow.

Of the licences subject to a restriction, 80% had been notified to cease abstraction by 10th July and all were restricted by 23rd August. This would have significantly reduced demands during the height of the regulation season. Maximum spray irrigation abstraction upstream of Bewdley of around 100 Ml/d is likely to have occurred in early June, although the average * throughout the irrigation season would have been much lower, probably around 70 Ml/d.

4.2.6.6 Comparison of All Major River Severn Abstractions In addition to the three public water supply abstractions covered above,.there are three further major abstractions from the River Severn between Bewdley and Gloucester. At Gloucester, British Waterways abstract a large quantity into the Gloucester and Sharpness Canal. The majority of this water is then re-abstracted from the canal at Purton by Bristol Water Ltd to supply Bristol. The residual flow in the canal rejoins the River Severn at the estuary.

Figure 4.7 tabulates the monthly mean abstractions at each of the major River Severn sites, comparing the 1995 seasonal average with previous drought years. Total gross abstractions increased by 17% between 1989 and 1995, with Trimpley, Upton and Pufton showing the largest proportional rises. Figure 4.8 graphically shows the cumulative gross and net abstractions down river, where the net abstraction allows for sewage effluent returns. Bewdley, Gloucester (upstream of the canal abstraction) and the Severn Estuary have been included as reference points.

1995 Drought Report Page 51 Environment Agency - Midlands Region Bewdley Flow Ml/d StartRegulation 17/06/95 Hampton Figure4.6: Net AbstractionsUpstream of Bewdley (gross) Note the different scales on the flow and abstraction axes abstraction and flow the on scales different Notethe Trimpley (gross) showing Bewdley 5-day mean flow mean showing Bewdley5-day Iron bridge (net) ______Shelton (net) EndRegulation 11/11/95 5 Day Flow Day 5 Bewdley

Natural Flow Natural Bewdley Bewdley i i 0 - 500 - 0 1000

Abstractions Ml/d Figure 4.7 Major River Severn-Abstractions

AVERAGE TOTAL Hampton Worcester BWB ABSTRACTION Shelton Ironbridge Trimpley Upton Mythe Purton exc. Loade Barboume Gloucester . Ml/d BWB 1995 \ May 618 15 10 158 15 26 139 98 52 157 June 14 6 178 26 28 . 148 102 90 170 672 July 750 18 .8 , 191 81 18 154 87 268 193 August 761 20 18 188 67 18 150 100 301 200 September 681 14 17 .177 42 13 138 103 • 195 177 October 730 * 14 14 186 88 0 162 104 192 162 November 766 15 17 203 . 88 1 159 101 116 182

SEASON Jun-Oct 1995 16 . 13 184 ; 61 15 150 - 99 211 180 718 Jun-Oct 1989 15 > 17 181 30 28- 100 90 206 154 615 Jun-Sept 1976 15 est. 21 121 18 28 76 .• 76 332 147 502 CHANGE % Rise 1989*1995 0 -2 0 +100 -46 +50 +10 0 +17 +17

NOTE : The BWB Gloucester abstraction to.the Gloucester and Sharpness Canal has been excluded from the total abstraction sum'to avoid double counting with the Purton abstraction (from the canal). Residual flows in the canal, including intercepted natural River Severn tributaiy^iflows, are returned to the Severn Estuaty. Figure 4.8 :1995 River Severn Gross and Net Abstractions Showing Individual Site and Downeatchment Cumulative Abstractions Based on Average Abstraction Rates June to October 1995 800 -r •o | 700 -

' S 600 - D£ § 500 -

| 400 -

£ 300 -

S) 200 - u(0 o > 1 0 0 - - < 0 -L

I Shelton Ironbrfdge Hampton. Trimpley (Bewdley) Worcester Upton Mythe. (Gloucester) G&S Canal Purton (Estuary) I

GrossAbstractionH 16 13 184 61 15 150. ' 99 211 180

Cumulative Net — 16 17 201 262 262 235 386 485 317 526 _ 468

Cumulative Gross-- 16 29 213 274 274 290 440 539 539 750 719 4.2.7 Allocation of Regulation Releases

The allocation of Severn Regulation releases (above normal compensation requirements) for the regulation season is shown in Figure 4.9. Of the total 42403 Ml released, Clywedog Reservoir provided 75.4%, 11.4% came from the Vymwy Water Bank, and the Shropshire Groundwater Scheme contributed the remaining 13.2% (based on net rather than gross support).

Support of the 4 main abstractions upstream of Bewdley required 47%. of the total releases. A further 23% was required for environmental reasons, principally to maintain the Bewdley 5-day flow at 850 Ml/d so that flows downstream of Bewdley would be environmentally acceptable, allowing for further abstractions and effluent returns. The additional releases from Lake Vymwy to prevent saline intrusion during the spring high tides (see Section 4.2.4) have also been included in this category.

Operational releases accounted for 4% of the total release. The urgent maintenance work at Llyn Clywedog (Section 4.2.3) was the largest component. Other releases in this operational category include i) releases due to North West Water Ltd’s maintenance work at Lake Vymwy ii) the overlap of releases from Lake Vymwy and Llyn Clywedog to allow for timing uncertainties following a habitat sampling exercise downstream of Llyn Clywedog iii) Shropshire Groundwater Scheme borehole testing iv) groundwater drawdown and recovery measurement exercises, constraining the i flexibility of the Shropshire Groundwater. Scheme borehole operations.

The remaining 26% of die releases were surplus to minimum regulation requirements, and in this sense can be termed ’excess releases’. However, the required releases are modelled using best estimates of future variables, with a deliberate allowance for possible errors in these, estimates. Excess releases are inevitable in this real-time management system. Appendix 2 gives a description of the data gathering and modelling tools used to. determine the release requirements, and a discussion of the 1995 Severn Regulation release efficiency is given in. Appendix 4.

i

1995 Drought Report Page 55 Environment Agency - Midlands Region Figure 4.9 : Allocation of 1995 Severn Regulation Releases 17/06/95 to 11/11/95

Forecast Margin (Major. Abstractors). 5% Forecast Margin (NRA) 9% Releases for Abstractors Upstream of Bewdley 47% Rain After Release 12%

Operational Releases 4%

Environmental Releases 23%

Total Release During Regulation Season 42403-MI

(Excluding Compensation Releases) (Based on NET Shropshire Groundwater Scheme Releases) I

43: River Derwent Water Resource Management

4.3.1 Introduction to the River Derwent Water Resource Activities

The resources in the Derwent catchment are conjunctively managed by Severn Trent Water Ltd (STW) to ensure economical and reliable supplies under a Section 20 (Water Resources Act 1991) Operating Agreement. The Environment Agency (or NRA in 1995) are notified of STW’s release and abstraction strategy, offer advice, and monitor compliance with licence conditions and management agreements.

There are three principal reservoirs in the Derwent System The Derwent Valley Reservoirs in the upper reaches of the Derwent provide direct supplies to Severn Trent and Yorkshire Water. Compensation releases to the Derwent are required, but additional releases can be made to support downstream abstractions. The reservoirs^fi Unnaturally ^assisted by-tributary'di vers ions. ; Ogston Reservoir in the River Amber tributary catchment is also used for direct supply. Its natural inflows can be boosted by pumped inflows from the River Derwent at Ambergate. Carsington Reservoir, over the watershed in the neighbouring Dove catchment, was constructed primarily for supporting the Derwent flows, and was first available for the 1994 season. Regulation releases are made to maintain a flow at Derby of 340 Ml/d, enabling licensed abstractions to continue and averting increased compensation; releases from the Derwent Valley Reservoirs. It has some natural inflow, but most of • its resources are pumped from the River Derwent at Ambergate in the wintertime for release in the summer. Carsington water can also be transferred to Ogston treatment works to conserve Ogston Reservoir storage, or to assist when water quality problems arise.

The principal Severn Trent Water Ltd public water supply abstractions from rivers in.the Derwent catchment are Meerbrook Sough at Homesford : most of the flow from this mine-drainage tunnel is abstracted for supply. River Derwent at Ambergate : abstractions can take place for pumped refill of both Ogston and Carsington reservoirs. Maximum allowable abstraction rates are dependent on flows at the downstream Derby gauging station. Abstraction rates are limited to just 15 Ml/d when the flow at Derby is between 340 and 680 Ml/d. River Derwent at Little Eaton : there are separate abstractions to Little Eaton treatment works for local Derby supply, and to Church Wilne bankside storage reservoir for Nottingham supply. Maximum allowable abstraction rates are again dependent on flows at Derby. River Derwent at Draycott-: this is an altemative>to:the Little Eaton abstraction point for Church Wilne supplies, situated further downstream with additional resources available from natural catchment runoff and Spondon (Derby) sewage effluent. Maximum allowable abstraction rates are dependent on flows at Church Wilne.

The sections below concentrate on details relating to the 1995 drought and comparisons with previous droughts.

1995 Drought Report Page 57 Environment Agency - Midlands Region 4.3.2 Overview of the 1995 River Derwent Operations

Heavy winter rainfall ensured the Derwent catchment water resources were in a healthy state at the start of the 1995 spring season, however, rainfall was exceptionally low from April to November at only 54% Long Term Average (LTA) over the Derwent catchment. This required active, coordinated management of releases and abstractions in order to maintain the residual flow of 340 Ml/d at Derby and make the best use of resources.

Figure 4.10 tabulates Severn Trent Water Ltd*s support release, transfer and abstraction quantities over the height of the drought period from June to October. Total support releases . and transfers by Severn Trent Water Ltd accounted for 26% of the total public water supply abstractions in the Derwent system.

SUPPORT / ABSTRACTION Equivalent Volume As % Total June to October 1995 Daily Rate Ml Abstraction Ml/d DERWENT VALLEY RESERVOIRS Releases to Derwent above compensation 109 0.7 0.2 CARSINGTON RESERVOIR Releases to Derwent 14215 93 21.0 Transfer to Ogston 3410 22.3 5.0

TOTAL SUPPORT (Severn Trent Water Ltd) 17734 116 26.2

RESERVOIR ABSTRACTIONS Derwent Valley Reservoirs for STW supply 22580 148 33.3 Derwent Valley Reservoirs for YW supply 6988 46 10.3 Ogston Reservoir for STW supply 3318 22 4.9 RIVER ABSTRACTIONS Meerbrook Sough at Homesford * . , 7937 52 11.7 Derwent at Ambergate to Ogston Reservoir 217 1.4 0.3 Derwent at Ambergate to Carsington Reservoir 0 0 0 Derwent at Little Eaton for Derby 8087 53 11.9 Derwent at Little Eaton for Church Wilne 15181 99 22.4 Derwent at Draycott for Church Wilne 3415 22 5.0

TOTAL ABSTRACTION (Severn Trent Water Ltd) 67723 443 100

KEY :STW Severn Trent Water LtdYW Yorkshire Water Ltd

Figure 4.10 : River Derwent Support and Abstractions by Severn Trent Water Ltd

This was the first major drought since the new Carsington Reservoir first filled at the end of 1993, and the resources proved to be essential in meeting unprecedented demands. Releases from Carsington to the Derwent took place virtually every day from mid June to early November. Additionally, transfers direct to Ogston Treatment Works helped conserve storage at Ogston reservoir. With Carsington being used to support the Derby 340 Ml/d maintained flow, additional releases from the Derwent Valley Reservoirs above normal compensation were made on only 8 days.

1995 Drought Report Page 58 Environment Agency - Midlands Region The Derby 340 Ml/d flow threshold, controlling maximum allowable abstraction rates and Derwent Valley compensation requirements, was maintained on all but 11 days in 1995. On most of-these occasions, the measured flow was only a few Ml/d short o f the target. Severn Trent Water’s (STW) slight errors of judgement in estimating natural flow recessions and release travel times account for some of the shortfalls. However, turbine and sluice gate operations beyond STW’s control, particularly at Belper Pound, account for the more serious low flows.

Severn Trent Water Ltd imposed a regionwide hosepipe ban on 22nd August, which'resulted in significant reductions in demand, although this also coincided with a period of cooler, damper weather. The regionwide ban was not lifted in the East Midlands until 29th April 1996.

The reservoir resources coupled with STW’s improved grid transfer system were sufficient to maintain supplies(withithe"hosepipeban iniforce) through the 1995 drought, but ended the season severely drawn down. The minimum storage reached at the Derwent Valley Reservoirs (20.2%) was lower than all previous recent droughts, but Ogston Reseivoir storage was less severely affected since raw water transfers from Carsington reservoir provided much of the supply to Ogston treatment works.

Following the prolonged low flow season and continuing below average rainfall, Drought Orders were required to assist refill at the Derwent Valley and Carsington Reservoirs. These, ran from mid January to mid April 1996.

Winter rainfall from October 1995 to-March 1996 was only 70% LTA over the Derwent catchment With the Drought Orders in force, reservoir storages had recovered to just 60.7% at Derwent Valley, 70.3% at Ogston and 73.0% at Carsington by 1st April 1996. These figures compare with average storages of 97%, 88% and 92% respectively for the time of year (the Carsington average has been estimated based on idealised operation).

A diary of the significant Derwent resource management activities and events is included in Appendix 5, covering details of the rainfall, reservoir storages, abstractions, releases and problems.

/995 Drought Report ■ Page 59 Environment Agency - Midlands Region 4.3.3 Derwent Valley Reservoirs

Heavy rainfall during December, January and February of 156% LTA ensured rapid winter refill of the Derwent Valley reservoirs, with overflows peaking at over 3500 Ml/d on 28th January. Flood drawdown releases continued until mid April. With low rainfall over the summer months, however, demands on the reservoir’s resources greatly exceeded inflows. The naturalised inflows to the Derwent Valley Reservoirs were the lowest on record over the April to November period, with a return period estimated at over 1 in 100 years. -The reservoir storage depleted at a rate of 3.4% per week at the height of the summer. Storage reached a minimum of 20.2% on 22nd December, lower than in any of the droughts since 1975.

The changes in storage and control curves for the Derwent Valley reservoirs (combined) from May toDecember’T995'areTshown‘ori Figure 4.1T, along'with*the'total releases measured'at Yorkshire Bridge just downstream of the dam. The diagram also illustrates the supply to Severn Trent Water-Ltd; and-Yorkshire; Water .Ltd;v

Additional releases from the Derwent Valley Reservoirs to support downstream abstraction took place for only one week in mid-June. Thereafter, Carsington resources were used in preference to maintain the 340 Ml/d flow threshold at Derby. This avoided the obligatory compensation rise from 57 to 75 Ml/d, and the Derwent yalley resources were conserved for direct supply..

Reservoir control curves recommend maximum supplies to Severn Trent Water Ltd and- Yorkshire Water Ltd depending on the storage and time of year to ensure sensible use of the resource throughout the season. The reservoir supply restrictions applied in 1995 were more severe than the control curve recommendations to conserve reservoir storage, and overall demands were met by increased river abstractions and grid transfers. Sustained rates of the STW supply, the largest single Derwent catchment abstraction, varied between 190 Ml/d in April and 105 Ml/d in October. Yorkshire Water Ltd supplies fell throughout the year from 55 Ml/d in May to 27 Ml/d in December.

Following the summer drought and continuing low rainfall over the Autumn and Winter months, STW were granted a Derwent Valley Reservoirs Drought Order on 19th January. 1996, running until 18th April. The Drought Order assisted refill by reducing the downstream compensation releases to the River Derwent at Yorkshire Bridge from 57 to 34 Ml/d, and to. the River Noe from 17 to 12 Ml/d (with a combined minimum reduced from 74 to 51 Ml/d), A similar Drought Order was in force in 1989, but started much earlier in October. Full details of the Drought Order are included in Appendix 1. By 1st April 1996, storage had only recovered to 60.7%, compared with an average storage of 97% for the time of year.

1995 Drought Report Page 60 Environment Agency - Midlands Region Supply Ml/d Total Storage % 100 ^ ^ - - 0 5 0 — 40 200 0 ----- 60 20 150 o e N v> ^ ^ v\>^ AN^ ^ ^ ^ - - r j i ...... ------IS*** IS*** \0 ^ ^ ^ o * ° ° * o ^ ^ ^ \0 IS***IS*** ' ^ n o ^ \ v N \ \* ^ o* n> ^ 'v N ^ T'W'TOrWjfWWi Yn'im ffATn'jTffff.mrmYnVWrfff iW W lTm'iWW'qTTOTrmWij ftW Derwent Release Derwent — ... SevernV V V VM H I frehTwaie^lSupp^y*',', V I I Iv 1 Yorkshire Water Supply Water Yorkshire ...... /* ...... d Figure 4.11: Derwent Valley Reservoirs Operations - May to December 1995 December MayReservoirs - to Operations Derwent Valley Figure 4.11: ...... ------...... - ... . \ N r-.^> . ^ ... . * \ ^ 2 < Storage,Release and Supply *>.*$> ^ ^ ...... - ^ p f ......

.-•■•■••A C0C ' *' 22/12/95 on J20.2% - -. ,rf^ ------= / - Minimum Storage Storage Minimum - «•* ...... 100^ ...... v o^ \ \> ^e>° *\0>i ^ ^ \0 vo ^ P j * ; /*•<** ; •*» . # N# . > # ■ III ■ ffllW l m rlyiTlTlWl rrri^TfTrnM rlyiTlTlWl m l ffllW ...... -"'v ...... ^ ..... ______,,--''155-45 _ ,,--''155-45 ...... [ 400-0 ...... [- 9 ^ MaxSupply Ml/d STW-YW _ •££-- * d 0 c 200 300 (3 100 500 0 W 50 200 150 150 Q □ , 0C ©

a

4.3.4 Ogston and Carsington Reservoirs and Ambergate.Abstractions and Releases

Heavy rainfall over the 1994/95 winter season filled Ogston Reservoir and Carsington Reservoirs without any need for pumped refill, providing maximum possible resources for the 1995 drought season.

The pattern of drawdown at Ogston and Carsington Reservoirs from May to December 1995 . is shown on Figures 4.12 and 4.13 respectively, together with relevant daily abstraction, release, transfer and supply information.

Low summertime rainfall considerably reduced natural flows in the Derwent, and releases from Carsington to the Derwent to maintain the 340 Ml/d flow at Derby and support lower Derwent abstractions were required almost continuously from mid June to early November. ------Release rates-exceeded-200-Ml/d'on~occasions; averaging aroundlOO Ml/d over the summer period. This wasthte first time the'Caisington resources had been available in a major drought summer. The releases allowed downstream abstractions at Little Eaton' and Draycott to continue, thereby helping to minimise public water supply difficulties. The daily releases from Carsington, the total river abstractions and the resultant Derby flows are shown on Figure 4.14.

t Due to algae problems at Ogston Reservoir, Carsington water was first transferred direct to Ogston treatment works during April and May. Further transfers direct to the works took place from mid June to late August to conserve Ogston Reservoir storage and improve the quality • of the raw water, while Carsington was simultaneously releasing water to the Derwent to support Derby flows. With no end to the drought in sight, the Carsington resources were then conserved for Derby support throughout the remaining drought period. Ogston Reservoir storage began a rapid descent at a rate of 4.8% per week with all the treatment works’ requirement being drawn from the reservoir, and the storage fell to its annual minimum of .28.2% on 29th October. This is slightly higher than in 1989 (27.9%) and 1991 (21.8%),-but lower than in 1984 (45%) or 1975/6 (30%). The Carsington to Ogston treatment works transfer recommenced after a two month break on 30th October, allowing the reservoir storage to slowly recover. Ogston works supply varied little throughout the season, averaging 44 Ml/d.

End of season pumped refill of Ogston Reservoir began in late November, but with Derby, flows between 340 and 680 Ml/d, abstraction rates were restricted to just 15 Ml per day. Since it is impossible (due to shared pipework) to simultaneously pump from the Derwent into Ogston Reservoir and transfer water from Carsington to Ogston works, the two activities took ,place for approximately 8 and 16 hours a day respectively at instantaneous rates of around 45 Ml/d. Pumped refill to Carsington occurred on only 4 days in 1995 when Derby flows rose above the 680 Ml/d threshold following rain.

Reservoir stocks were severely depleted following the dry summer, and low rainfall over the Autumn and early Winter season resulted in a slow storage recovery rate. Severn Trent Water Ltd were granted an Ambergate Drought Order on 19th January 1996, running until 18th April 1996. Full details of this Drought Order are given in Appendix 1. The Drought Order assisted refill of Carsington and Ogston Reservoirs by reducing the Derby flow threshold that allows high rates of pumped storage abstraction from 680 to 500 Ml/d. This resulted in around 2600 Ml of additional pumping during March and April 1996, equivalent to 7% of the Carsington Reservoir capacity. Most of these additional resources were pumped to Carsington rather than Ogston as this reservoir receives very limited natural refill. By 1st April 1996 Carsington had recovered to 73% full, and Ogston was 70% full.

1995 Drought Report Page 62 Environment Agency - Midlands Region Storage % Full 100 0 * - 40 20 — 60 0 — 80 • - Figure 4.12 : Ogston Reservoir Operations - May to December 1995 December to May - Operations Reservoir :Ogston 4.12 Figure Storage,Supply, Carsington andTransfer InflowPumped Ambergate Note: The transfer from Carsington Reservoir goes direct to Ogston treatment works,not to OgstonReservoir, but the supply volumes include bothsources Ogston %Full gthTetet ewn Transfer Derwent OgstohTreatment o k u py Pumped From .Works CarsingtonInflow Supply a ------40 200 r - 80 - 160 - 120

Abstraction / Supply / Transfer Storage % Full 100 40 20 60 80 - 0 — Figure 4.13: Carsington Reservoir Operations - May to December}Mayto- Operations Reservoir Carsington1995 Figure4.13: Storage, Transfer toOgston, Derwent Release, Ambergate Pumped Inflow ^ ^ 0“ .O5" ^ ^ 0#“ ^ ^ 1 V Carsington % Full% toOgston Treatment Worksnot to'OgstonReservoir itselfThetransfer Note: fromCarsington to Ogstongoes direct to Ogstonto Transfer to Derwentto i i I __ ees Derwent Release _ ____ i Pumped InflowPumped ^ ^ p £

®! <£ 0 o®°! Releases I Abstractions / Flow Ml/d -300 -200 400 0 — 500 — 600 0 — 700 300 200 800 100 100 0 - S E S A E L E R - - | ik i i k i i i h i . | ii n i; : |i ii i i ; m i , i Figure 4.14 : River Derwent at Derby - May to December 1995 December to May - Derby at Derwent : River 4.14 Figure 1 i i i i | i i i i i i i i i k i i | i i i : , i i n ■; i i |, i , i t i i!!! , [Tn 11| u | n ’, i i. i i 111111 [iin r,T,T , 7 in h 1111 River AbstractionsReservoirandReleases ...... i, i h i j h 111 ; h i i m 11 i 1111, i i i , i 111; : ; i i 11, . u i 111, i h 111111m , i n u ^ 111, . , ,i i 1111, h 11 | , i 111, u m , ,i i i , i 11 800 4.3.5 Little Eaton and Draycott Abstractions

Figure 4.15 shows the daily pattern of the Severn Trent Water Ltd (STW) river abstractions for the principal sites upstream , of Derby compared to the prescribed flow. Figure 4.16 illustrates abstractions in relation to the Church Wilne flow. Combined STW river abstractions from the sites upstream of Church Wilne averaged 228 Ml/d from June to October, but varied between 113 and 285 Ml/d; The releases from Carsington to the Derwent represented 53% of the Little Eaton and Draycott abstractions over the June to October period.

Both Little Eaton abstractions (to Derby via Little Eaton treatment .works, and to Nottingham via Church Wilne bankside storage reservoir) are restricted by the flow at Derby. The abstraction point at Draycott further downstream,,, an .alternative-route-to-Church-Wilne- ” Reservoir, is also controlled by the same flow thresholds measured at Church Wilne gauging station rather than Derby. Since this is downstream of Spondon sewage works and has a larger contributing catchment-area; flows: at,Draycott:,were generally at least 100 Ml/d higher than at Derby during n the summer of 1995. Thus, by transferring the Church Wilne Reservoir abstraction point from Little Eaton to Draycott, Church Wilne demands could be met with lower releases from Carsington Reservoir. Pumping costs at the Draycott abstraction point are lower, however, water quality is significantly impaired by the sewage effluent.

Derwent abstractions to Church Wilne Reservoir are the second largest abstraction in the Derwent catchment, and represent the largest river (rather than reservoir) abstraction, peaking at over 170 Ml/d. Until early August, all the Church Wilne supplies were taken at Little Eaton. ■ As the drought continued and Carsington resources were being depleted, about a third of the Church Wilne demand was taken from Draycott. By early November, Draycott intake supplied the majority of the demand, helping to eliminate the need for Carsington’s derby support releases. Draycott continued to be the principal abstraction point during the following winter . and spring period.

The smaller abstraction at Little Eaton for Derby supply peaked at over 60 Ml/d during the hot spells in July and August, averaging 53 Ml/d over the whole drought period.

1995 Drought Report Page 66 Environment Agency - Midlands Region 4.3.6 Turbine and Sluice Operations

When Derwent flows are low, the effects of sluice gate and turbine operations in the river are enhanced. This was a particular problem at Belper Pound where the Derwent is impounded by a long horseshoe-shaped weir and sluice gate arrangement,\with a mill race to electricity- generating turbines. A more detailed description„of the Belper Pound set-up and operational. effects is given in Appendix 6, and individual events are covered in the Derwent Diaiy section, Appendix 5.

Norvveb Generating activities at Belper caused many serious flow fluctuations during the low flow season. A great deal of staff time (both NRA and Severn Trent Water Ltd) was required during the Belper incidents, firstly, to separate Belper Pound effects from flow fluctuations caused by intermittent abstractions and releases; secondly, to determine abstraction and release plans to maintain the Derby 340 Ml/d threshold flow; and thirdly, to monitor levels, flows and rates of pound ;refill:^The NRA were; able: to radvise: during the event by monitoring the interrogable data loggers measuring the abstractions at Ambergate and Little Eaton; the level at Belper Pound and the flow at Derby

Severn Trent Water Ltd (STW) and Courtaulds Ltd were both helpful in alleviating possible quality problems resulting from Belper Pound interference. Courtaulds agreed to temporarily recirculate warm water rather than abstract new supplies for cooling. STW had to limit their , abstractions due to the activities at Belper Pound on several occasions. They were particularly; concerned when pound emptying and subsequent refilling took place whilst they were, releasing from Carsington Reservoir. In effect, the Carsington releases (available through expensive pre-season pumping) were being used to refill the pound, rather than to allow increased abstractions downstream. < t J ' . The most serious Belper event of the summer followed the accidental emptying of the pound when a sluice gate became stuck. Derby mean daily flows reached a minimum of 262 Ml/d on 12th September, with an instantaneous minimum flow of 106 Ml/d. Fortunately, no quality or biological problems were reported.

Low levels were a threat to water quality and biology on the Spondon meander stretch of the . Derwent in July. The Spondon flood sluices across the neck of the river meander had stuck open, severely limiting the flow around the meander. Courtaulds Ltd make a large abstraction here just above the Spondon (Derby) sewage effluent outflow, and return most of the abstracted water shortly downstream of the sewage works. This resulted in potential quality problems due to insufficient dilution of the sewage effluent in the meander locality resulted.

1995 Drought Report Page 67 Environment Agency - Midlands Region Flow or Abstraction Ml/d 200 400 500 300 600 100 800 Figure 4.15: River Derwent FigureDerby at -May December1995to4.15: en DailyFlowsMean MajorandUpstreamRiver Abstractions Derby Flow Homesford iteEtn LittleEaton LittleEaton o eb t hrhWle Ogston/Carslngton toChurch Wilne forDerby Ambergateto Flow or Abstraction Ml/d 1000 400 700 600 800 500 200 300 900 100 0

ffiTnTnTITr 340 Ml/d340 n Y l w f m T p T n T m w Figure 4.16 : River Derwent at Church Wilne - May to December 1995May- toDerwent: River Figure atChurchWilne 4.16 Mean Daily Flows and Major Upstream River Abstractions iffmnTmY Church Wilne Draycott to Total Major Total River Abstractions Draycott to Church Wilne lw hrhWle Upstream Derbyof Church Wilne Flow TT m 4.4 Tittesworth Reservoir and Leek Area Water Resource Management

4.4.1 Introduction to the Leek Conjunctive Use Scheme .

The resources in the Leek area are a major source of supplies for parts of North Staffordshire and the Potteries. The reservoir and borehole conjunctive use system is managed by Severn Trent Water Ltd (STW) but is not fully linked to their regional water supply grid. Consequently, all the demands have to be met by appropriate allocation of the local resources. The Environment Agency are not normally involved in the day to day. operations, but periodically monitor abstraction licence compliance.

______There are three principal components to the Leek system - a reservoir, supply boreholes and , compensation boreholes? Tittesworth Reservo irin the upper' reaches of the Chumet catchm ent— is a naturally filling direct supply reservoir. A group of six boreholes around the town of 1 Leek, downstream/of/Tittesworth:-'Rieservoir, can = pump groundwater from the underlying Sherwood Sandstone. Four of these boreholes (Highgate, Pool End and two at Wallgrange) pump to a local service reservoir to supplement the Tittesworth Reservoir supplies. The borehole at Abbey Green is not normally used due to the acidity of the water. A borehole at Deep Hayes and a new well at Wakefield are also available to provide River Chumet compensation releases, but are not licensed. The reservoir and borehole compensation releases required under normal conditions are shown on Figure 4.17. The minimum compensation releases required from Tittesworth Reservoir to meet the total system compensation requirements is dependent on the natural inflows from tributaries downstream of the dam.

4.4.2 Overview of the 1995 Tittesworth Operations > .

The changes in reservoir storage, direct supply and compensation releases from May to December 1995 are shown graphically on Figure 4.18.

Rainfall over the preceding winter was heavy, with the'Upper Trent subcatchment receiving 166% of long term average (LTA) rainfall from December 1994 to February 1995. Tittesworth Reservoir soon refilled and remained full until early April. Rainfall from April to August was only 35% LTA, however, and the reservoir storage fell at a rate of 3.3% per week through the spring and summer months. The rainfall shortage reduced runoff from the Deep Hayes catchment, necessitating high compensation releases from Tittesworth Reservoir approaching 19 Ml/d at the end of August. As the reservoir storage fell, , the direct supply abstraction reduced from 35 Ml/d in May to 7.5 Ml/d by mid August to conserve the reservoir storage. Abstractions from the four supply boreholes in the Leek system increased from 20 Ml/d to 28 Ml/d over the same period to compensate, and total supply demands were met with support from groundwater sources further afield.

Severn Trent Water Ltd imposed a regionwide hosepipe ban on 22nd August. In combination with the onset of cooler, damper weather, this resulted in a 10% demand reduction over the Stoke District. The rainfall deficit continued over the Autumn, however, and reservoir abstraction for supply effectively ceased on 27th November, after the reservoir reached its minimum storage of 14.8% on 11th November. This was much lower than in the recent drought years of 1989 (23%), 1984 (40%), 1976 (45%) and 1975 (28%).

1995 Drought Report. Page 7.0 Environment Agency - Midlands Region Following the prolonged low flow season and continuing below average rainfall, Severn Trent Water Ltd were granted a Tittesworth Drought Order to assist reservoir refill, running for six months from 29th December 1995 to 29th June 1996. The effects o f this Drought Order on the required compensation releases are tabulated on Figure 4.17. Full details of the Drought Order are included in Appendix 1.

Compensation Requirement Source or Location Normal Conditions 1995 Drought Order Conditions River Chumet at Solomon's Hollow 1 min 14.8 Ml/d min 5.0 Ml/d (ie. Tittesworth Res comp, release and trib. inflow) Abbey Green Borehole zero (licensed for max 10.0 Ml/d supply but not used) SUM SOLOMON’S HOLLOW + ABBEY GREEN ' 1 min 14.8 Ml/d min 14.0 Ml/d 2

Deep Hayes catchment natural runoff natural runoff Deep Hayes Borehole zero (not licensed) max 4.5 Ml/d (New) Wakefield Well zero (not licensed) max 2.0 Ml/d

TOTAL COMPENSATION min 19.3 Ml/d 2 min 18.0 Ml/d 2 1 note that this Is NOT the old Solomon’s Hollow gauging station on the tributary 2 note that this flow is not necessarily equal to the sum of the compensation components above

Figure 4.17 : Compensation Requirements of the Tittesworth and Leek System.

The Drought Order compensation requirements allowed operational flexibility, and enabled reduced reservoir and borehole compensation releases when natural tributary inflows were high. The Drought Order gave only a slight reduction in the total compensation, but increased the groundwater support component to allow reduced compensation releases from the reservoir. This saved resources equivalent to 4% of the reservoir storage for every month the Drought Order was in force. In 1989, a similar Drought Order was required for Tittesworth Reservoir, but it came into force much earlier, in early September.

At the close of 1995, the reservoir storage had recovered slightly to 29.9%. With the Drought Order in force, compensation from the base of the dam could be reduced -to below 0.2 Ml/d on the wetter days in February and March 1996. Reservoir abstraction to supply recommenced on 1st March 1996 at a rate of 15 Ml/d after the reservoir storage has recovered significantly. Despite winter rainfall from October 1995 to March 1996 of only 70% LTA over the Upper Trent catchment, the Drought Order enabled Tittesworth Reservoir storage to recover to 82.4% by 1st April. 1996, although this fell significantly short of the average storage of 98% for the time of year. The hosepipe ban was not lifted in the Stoke District until 29th April 1996.

199S Drought Report Page 71 Environment Agency«- Midlands Region Storage % Full 100 20 40 0 - 60 0 — 80 - ...... u11m n I |mmTl n n|MmimiTll Figure 4.18 : Tittesworth Reservoir Operations - May to December 1995 December to May - Operations Reservoir :Tittesworth 4.18 Figure i THT i TH iij T ij miTilTi Storage,Supply andCompensation 20 — . 40 —. 80 - 60 100

Supply or Compensation Ml/d 4.5 Other Water Resource Systems

4.5.1 The River Leam System

4.5.1.1 Background Draycote Water reservoir has limited natural inflows, but pumping from the River Leam at .Eathorpe can take place in the winter period (15 September to 30 April) at rates up to 182 • Ml/d. If reservoir storage is particularly low, control rules allow the pumped inflows to continue into the summer season at reduced maximum rates of 120 Ml/d. However, the pumped inflow abstractions are always constrained by the prescribed flow of 18.2 Ml/d at Leamington.

The reservoir resources are used primarily for direct supply to Rugby, in conjunction with Stanford Reservoir resources and an abstraction from the River Avon at Brownsover. In addition, the Draycote-Resources^are;used to support raw water supplies to Campion Hills treatment works. Severn Trent Water Ltd manage these resources under a Section 20 (Water Resources Act 1991) Operating Agreement

The majority of the Campion Hills treatment works raw water supply is pumped from the River Leam upstream of the Leamington flow gauge, via Willes Meadow bankside storage reservoir, at rates up to 91 Ml/d. This all-season abstraction is also constrained by the Leamington prescribed flow. When river flows are low, releases from Draycote Water to the Leam at Eathorpe can be made to support the river abstraction to Willes Meadow. Alternatively, Draycote resources can be transferred directly to the treatment works or to the bankside storage reservoir through a new raw water pipeline link. This pipeline, newly available in 1995, frequently transfers limited quantities to sweeten the Willes Meadow water which is higher in nitrates.

4.5.1.2 1995 Operations Pumped refill took place throughout the winter of 1994/95 but low flows in the River Leam limited abstractions during March and April, and Draycote Water started the 1995 summer season at around 85% full.

Releases from Draycote into the Leam at Eathorpe to support the Willes Meadow abstraction commenced on 23rd July at a rate of 8 Ml/d. Releases peaked at 15 Ml/d early August but ceased on 6th September, giving a total of 46 days support. These releases enabled the Willes Meadow abstraction to continue at normal rates of around 24 Ml/d, but the abstraction was cut to around 20 Ml/d in September after the river support ceased. The prescribed flow at Leamington was maintained throughout 1995.

Pipeline transfers.from:Draycote Water to Willes Meadow commenced in mid July at rates of just a few Ml/d until November. The transfer rose over the winter months, however, peaking at 21 Ml/d on 27th December, but returned to low rates from mid March 1996.

Severn Trent Water Ltd were riot obliged to use the river release route (rather than the ‘ pipeline route) to support Campion Hills treatment works with.supplies from Draycote Water in the summertime. They were encouraged by the NRA to choose this transfer option due to the considerable environmental benefits of the resulting increased river flows in the Eathorpe to Leamington reach. This could highlight the need for a revised operating agreement.

1995 Drought Report Page 73 Environment Agency - Midlands Region Draycote water reached a minimum storage of 55.5% on 26th November. This was higher than the 1989 minimum of 47% when the reservoir was deliberately drawn down for maintenance work. Pumped refill of Draycote Water recommenced on 11th November, but, due to the Leamington flow constraints, refill abstractions did not rise above 80 Ml/d until 22nd December, resulting in an end of year storage of 62%. Inflows peaked at 103 Ml/d during mid February. By 1st April 1996 storage stood at 86.1%, average for the time of year, and pumping therefore ceased at the end of the normal licenced period.

4.5.2 The River Dove System

4.5.2.1 Background Severn Trent Water Ltd own and manage the Dove Reservoirs (Foremark. and Staunton Harold), whose storage is used entirely for public water supply. The reservoirs have negligible ------natural catchment and are fed by pumped abstractions'from the River Dove at Egginton—The- maximum allowable-abstractionr:is controlled'by:.ther:gauged flows on the River Dove at Marston and on the Rolleston Brook at Rolleston, both upstream of the abstraction point. When Marston flows fall below 390 Ml/d, the normal maximum allowance of 230 MI per day , is reduced to the excess above a combined prescribed flow of 159 Ml/d at Marston and Rolleston. Licence conditions and reservoir storage control rules allow a reduced prescribed flow of 90 Ml/d when storage is critically low.

4.5.2.2 1995 Operations The changes in reservoir storage, direct supply and compensation releases from May to ; December 1995 are shown on Figure 4.19.

The Dove Reservoirs were 92% full at the start of May and pumped inflows continued unrestricted until 21 June, when Marston flows first fell below the 390 Ml/d threshold. The Egginton abstractions had previously taken place at maximum rates to meet the high demands, but had to be cut initially to around 170 Ml/d. The reduced inflows caused the combined . reservoir storage to fall at a rate of 5% per week during July. Through August, the abstractions were restricted to an average of 90 Ml/d as Marston flows plummeted to around 240 Ml/d. The reservoir storage crossed into the lower prescribed flow zone for a few days in late August and early September. The reservoir drawoff via Melbourne treatment works was cut from 225 Ml/d in August to 197 Ml/d in September, and fell to 180 Ml/d by the end of the year.

Combined reservoir storage fell to a minimum of 43.1% on 9th November, compared to 69% in 1989. Rains finally arrived in November and December, raising the Marston flow and allowing maximum abstractions such that the storage had recovered to 55% by the end of 1995 with pumped inflows some 40 Ml/d in excess of supply. By 1st April 1996, storage stood at 86% full, above average' for the time of year.

There were 9 occasions in the summer months when the residual flow (ie Marston plus Rolleston minus the total Egginton abstraction) fell below 159 Ml/d. Most of these shortfalls .were only slightly below the threshold due to Severn Trent Water Ltd’s forecasting errors, but on 20th September the residual flow was 100 Ml/d short of the prescribed flow, with Egginton abstractions totalling 212 Ml/d. The reservoir storage was not in the reduced prescribed flow control region at this time. Severn Trent Water Ltd were not prosecuted, however.

1995 Drought Report Page 74 Environment Agency - Midlands Region Figure 4.19 : Dove Reservoirs Operations - May to December 1995 Storage, Supply, Pumped Inflow and Marston Residual Flow

rflTrffffiT| rrn rn rnnrn | [rnWrmTiTr f i nrnriTnn^ i ith n ri n rr | iTrnTrrnrn i | rfn ini hiti |in.ii Q 4.5.3 Charnwood Reservoirs

The naturally filling Chamwood Reservoirs (Cropston and Swithland) impound the Quom Brook in the Soar catchment, and contribute towards Severn Trent Water Ltd’s supply to Leicester.

The storage was 85% of capacity at the start o f April, and began to cause concern early in the season with drawdown beginning earlier than usual. Output from Cropston treatment works was reduced in April, and all the usable storage in Swithland Reservoir was transferred to Cropston during May to conserve stocks for the anticipated high demands later in the summer. Output had to be temporarily increased for short periods to meet the exceptional supply demands in June and August.

Rainfall over the Soar catchment was proportionally the lowest in the region at only-28% average from Aprii;to August. The;combinedstorage: of the two reservoirs reached a minimum of 17.8% on 2nd November, compared with 49% in 1989. The treatment works operated with a minimum throughput of 12 Ml/d in November, and was totally rested from 19 December to improve refill prospects. By the end of 1995, storage had only recovered to 29.9% full. On 1st April 1996, the storage stood at 80.2%, compared to an average of 92% for the time of year, and was still causing Severn Trent Water Ltd some concern.

The treatment capacity at Cropston works has recently been increased to 35 Ml/d. This allows the reservoirs to be used as a ’peak lopping’ source by increasing drawoff for short periods to meet the high summertime demands in the Leicester area.

4.5.4 Blithfield Reservoir

Blithfield Reservoir is owned by South Staffordshire Water Ltd, and is their only major reservoir resource. The Blithfield supply is used in conjunction with the River Severn abstraction at Hampton Loade and local borehole sources to supply South Staffordshire Water Ltd’s command ara. The reservoir is mainly naturally filling, but is also partially pump filled from an abstraction at Nethertown on the River Blithe.

The reservoir storage began the 1995 season at 99% full, but reached a minimum of 35.2% on 20th October. The drawdown was greater than in the previous recent drought years of 1989 to 1991 (46%) and 1975 to 1976 (45%). The catchment.received less than half the average rainfall in the April to November period. As wetter weather increased natural inflows, the storage recovered to 49.3% by the end of the year, and was 79% full on 1st April 1996.

4.5.5 Elan Valley Reservoirs

Although the Elan Valley reservoirs in mid Wales are outside the Severn and Trent catchments, the raw water transfer via the Elan Valley Aqueduct to Frankley treatment works supplies the majority of the demands for Birmingham. When storage at the Elan Valley Reservoirs falls, aqueduct supplies are limited by control rules and additional abstractions from the River Severn at Trimpley (or elsewhere) are required. This has significant implications for River Severn Regulation.

1995 Drought Report Page 76 Environment Agency - Midlands Region The Elan Valley reservoirs started the season full, but by August maximum transfers to Birmingham and full River Wye regulation releases were taking place, resulting in a 23% fall in storage over the month. Elan Valley transfers to Frankley had to be supplemented with increased Trimpley abstractions to meet peak demands early in the Summer. Reservoir transfers were temporarily reduced to conserve storage during September when high river flows following rainstorms allowed large abstractions at Trimpley. The raw River Severn (Trimpley) water was transferred via the aqueduct to Frankley to make up the Elan deficit.

The reservoir storage reached a minimum of 32.5% on 25th September, compared to 41% in 1989, 33% in 1984 and 30% in 1976. Storage had recovered to 56.2% by the end of the year. Heavy rains fell over this part of Wales in January and February 1996, enabling the reservoirs: to fill by 25 April 1996.

4.5.6 The River Blythe System

The flow measurement station on the River Blythe at Whitacre operated by Severn Trent Water Ltd controls their abstraction to Whitacre Reservoir. When the flow at Whitacre falls below the prescribed flow of 23 Ml/d, upstream gravity abstractions must cease and only more expensive pumped abstractions from the Blythe just before its confluence with the River Cole can take place. Further inputs to the Whitacre and Shustoke reservoir system are pumped from - the Bourne Brook tributary to the River Cole, subject to a prescribed flow of 2.27 Ml/d.

Gravity abstractions from the Blythe first ceased in late June and did not fully recommence > until November. Pumped abstractions took place for most of the year peaking at over 30 Ml/d in October. River Bourne abstractions were gradually reduced as river flows fell from around 12 Ml/d in the spring, until no abstraction could be made by mid September.

1995 Drought Report Page 77 Environment Agency - Midlands Region 1995 Drought Report ' page 78 Environment Agency - Midlands Region CHAPTER S : OTHER WATER RESOURCE ASPECTS

5.1 Public Water Supply

5.1.1 Introduction

Hot weather, prolonged rainfall deficits and resulting low flows can cause severe public water supply difficulties, both in terms of maintaining supplies throughout the summer and in meeting the peak demands experienced when hot, dry weather leads to widespread use of hosepipes andj sprinklers. When faced with high demands, depleting reservoir storages and river abstraction restrictions, a major public water supply utility will have to find resources elsewhere, or to take action to reduce the supply demand. If alternative sources are similarly stretched, Hosepipe Bans and Drought Orders will inevitably result

Severn Trent Water Ltd and South'Staffordshire. Water Ltd are the two principal public water supply companies operating in the Severn and Trent catchments, however, other neighbouring companies have abstraction or supply operations in the Region. These include Welsh Water, North West Water, Yorkshire Water and Anglian Water. Severn Trent Water Ltd have a much larger supply area than South Staffordshire Water Ltd, and provide most of the sewerage services in the region. A third principal company, East Worcestershire Waterworks Company, was taken over by Severn Trent Water Ltd in 1994. - r * ' 5.1.2 Overview of Public Water Supply Operations in 1995

Despite the hot weather, prolonged dry spells and record demands, there were no piajor water supply interruptions over the drought period. The supply systems were stretched, however, and some short lived, localised problems did occur, due to limitations in the treatment and distribution facilities rather than to a lack of raw water resources.

Media appeals for water conservation began at the end of June, but, following the privatisation of the water industry in 1989, the public were not as responsive to these appeals as they had been in the 1976 drought. Consequently, demands rose to record levels during the hot diy period and remained high until Severn Trent Water Ltd imposed a regionwide hosepipe ban at the end of August.

No summertime Drought Orders were required, but winter Drought Orders were obtained to safeguard supplies for 1996.

Figure 5.1 illustrates the weekly variation in demands over 1995 for the two companies, with average weekly temperatures in Birmingham for comparison. The weekly demands are also expressed as a percentage of the annual average, to emphasise the variations.

1995 Drought Report Page 79 Environment Agency - Midlands Region Figure 5.1 : Average Weekly Public Water Supply Demands 1995 for Severn Trent Water Ltd and South Staffs. Water Ltd showing the variation in weekly mean temperature at Birmingham Average Weekly Temperature In Birmingham C Degrees Birmingham In Temperature Weekly Average

Week Ending 5.1.3 Severn Trent Water Ltd Supply Activities in 1995

Demands were unseasonably high at the start of May with the first spell of warm dry weather, and increased during June in line with rising temperatures. Much of the additional demand can be attributed to garden watering. Demands peaked during the first week of July when Severn Trent Water Ltd (STW) experienced their highest ever demands. The weekly mean of 2552 Ml/d exceeded the previous record (1994) by over 120 Ml/d, an increase of 5%, and was some 21% above the annual forecast demand figure. The daily peak was 2750 Ml/di The second major demand peak late July to early August corresponded with daily maximum temperatures in Birmingham over 30 degrees for 5 consecutive days.

These exceptionally high peak demands stretched STW’s supply and distribution system. Despite the treatment plants providing maximum outputs, supply difficulties were experienced in some areas at this time, and the storage of strategic treated water fell to critical levels on several days. Thecproblems were principally due to limitations in the treatment and distribution facilities rather than a lack of raw water resources. Fortunately, raw water quality was generally good and stable, allowing enhanced peak outputs from some works. Treatment capabilities were improved when the new works at Trimpley came on line from the end of June, and the planned closure of Barboume works was delayed until the end of September when demands had subsided. ' ■ '

Public requests to save water, particularly through limited use of garden sprinklers, were made . through the media from the end of June, but demands only fell during cooler wetter interludes. . ' With all treatment works at maximum output and reservoir abstractions at greater than desirable levels considering the rapidly depleting storages, STW decided to announce a regionwide hosepipe ban over the weekend 19th/20th August (although it was not officially in force until 22nd). This produced an immediate reduction in demands of 5 to 6 %, and a change to cooler, showery weather brought a further fall of some 10% so that demands were back to annual forecast levels by the end of August, and remained fairly constant for the rest of the year.

As the drought progressed, STW operated a policy of maximising supplies from groundwater and river abstraction sources and reducing outputs from impounding reservoir sources. This strategy conserved reservoir storages and avoided any summertime Drought Order applications, but the operational flexibility in the distribution grid was restricted.

With reduced drawoff from the Derwent Valley Reservoirs, reverse flow in the Derwent Valley aqueduct was required to enable local demands to be met, and frequent use was made of the poorer quality Draycott abstraction point on the River Derwent to maximise river abstractions.

Following the dry Summer and Autumn, STW obtained winter Drought Orders to assist refill of Tittesworth, Ogston, Carsington and the Derwent Valley reservoirs to safeguard supplies for the summer of 1996.

The hosepipe ban was eventually lifted over most of the region on 19th January 1996, but was not finally lifted in the East Midlands and Stoke districts until 29th April 1996. In an attempt to restrict future demands without necessarily imposing hosepipe bans, STW now insist that all customers using domestic garden sprinklers have metered supplies.

1995 Drought Report Page 81 Environment Agency - Midlands Region 5.1.4 South Staffordshire Water Ltd'Supply Activities in 1995

Although the South Staffordshire Water Ltd (SSW) supply area falls in the region with the highest summer rainfall deficits, with much of the supply area receiving less than half the average April to November rainfall, the company did not impose a hose pipe ban nor seek any Drought Orders in 1995.

Approximately half of the company’s supplies come from groundwater sources which were not immediately seriously affected by the 1995 drought.

Blithfield Reservoir is South Staffordshire W ater’Ltd’s only reservoir resource. The dam impounds the upper reaches of the River Blithe and the reservoir is mainly naturally filling. ------Storage-suffered Jn ,1995jdue_to the high demands jrnd low inflows, but alternative resources - ensured continued supplies. ^

The company’s principal, river abstraction is on the Severn at Hampton Loade, where the required abstractions were met by River Severn Regulation support releases. A new abstraction licence allowing SSW a further 60 Ml/d at Hampton Loade (provided Severn Trent Water Ltd’s Trimpley abstraction is 60 Ml/d below its maximum), is detailed in Appendix 2. The additional allowances were utilised on many occasions in 1995, particularly non-regulating days. The company’s only other river abstraction is from the River Blithe at Nethertown for pumped refill of Blithfield Reservoir.

Peak weekly demands of 423 Ml/d occurred around the same time as the STW peak, and * demands similarly fluctuated with changing weather and temperature conditions. Although the STW regionwide hosepipe ban did not apply in the SSW supply area, it would nonetheless have been heeded by many of their customers.

1995 Drought Report Page 82 Environment Agency - Midlands Region 5.2 Sprav Irrigation

5.2.1 Introduction

During hot, dry periods when river flows are at their lowest, abstraction demands are generally at their highest This inverse relationship between resources and abstraction demands increases the impact of a drought on the fanning community. Many agricultural river abstraction licences have clauses preventing abstraction when river flows fall below a prescribed flow threshold, and this can have serious financial consequences to a fanner who needs to spray irrigate his crops.

5.2.2 Overview of Spray Irrigation in 1995

The 1995 usage of surface water spray irrigation licences in the Severn and Trent catchments is detailed in Figure 5.2, below.'Assuming a 60 day: spray irrigation season, the abstractions would equate to an average of 115 Ml/d over the Severn catchment and 184 Ml/d over the Trent.

Catchment No. Licences Total Licensed Annual Total Reported Used (Surface Water Spray Quantity Annual Quantity Irrigation) Ml Ml (% of licensed) Severn u/s Bewdley 358 11066 4157 (38%) Severn d/s Bewdley 796 13067 2722 (21%) Total Severn 1154 24133 6880 (29%) Total Trent 851 22537 11047(49%) TOTAL 2005 45570 17927 (38%)

Note : i) data subject to unavoidable errors due to incomplete returns, combined licences, recent additions / cessations / alterations, such that the % used quantities are probably slight underestimates. ii) data refers to financial year (April to March) iii) Severn sub-catchments 1 to 5 used to represent abstractions upstream of Bewdley

Figure 5.2 : Regionwide Surface Water Spray Irrigation Licensed and Used Quantities 1995

The proportion of the licensed quantity used was 29% over the Severn and 49% over the Trent. Similar proportions were used in 1989, but the total surface water spray irrigation licenced volume has increased by over 20% in the Severn basin since 1989. The used / proportion is. influenced by the imposition of abstraction restrictions when river flows fall (where licence conditions allow). Those licences subject to such restrictions represent over a ' quarter of the spray irrigation licences, totalling 352 and 226 licences over the Severn and Trent basins respectively, compared to 222 and 45 in 1989. The used proportion calculation is also influenced by quantities allocated to licences that are never used but have not been surrendered. s

Figure 5.3 shows graphically the rise and fall of the number of licences restricted over the Severn and Trent catchments. The first restrictions were imposed in mid-June as the warm temperatures and dry weather from mid-March was reflected in falling river flows. Restrictions rose to a peak at the end of August, when 80% of possible restrictions were in force over the Severn basin, and 65% over the Trent. This partially accounts for the lower usage compared to licensed quantities over the Severn basin than over the Trent. With the onset of cooler, damper weather in September, restrictions began to be gradually lifted as flows recovered. The site-by-site details of the licence restrictions are tabulated in Figure 5.4.

/995 Drought Report Page 83 Environment Agency - Midlands Region Total No. of Restrictions In Force 200 - 300 400 0 0 1 - SevernBasin Max =352 rn BasinMaxTrent = 226 Cumulative Number of Restrictions In Force - Severn and Trent and Number Restrictions of Cumulative Severn - ForceIn NOTE:The 'maximum1 figuresquoted relate he summer possible to monthsrestrictions during Figure 5.3: Surface Water AbstractionLicences 1995 Mid-WeekDate Catchments —;——t- I ,..« vv .*v v*v v,v.;.y«■ .v«v. '.s*.v Catchment Catchment Severn Trent .1 ,\y/. /

Figure 5.4 : Licensed Abstraction Restrictions 1995 151 ii *1 n n < o i- »-: tm ■» r* •Zi: Si? 3isle . ^ i o - i=*■! v A i a . ! ! I «* «:*■>' «• «•«* «:*■>' g “ g £ ( * § j : I bPa I * 3 i : i i odvi^ -o^d v h -

s £ 4 4 g &£ £ 5*3ii°^«is^ SSi? 9 R oo-o o

;0 0 i oo o io A CM A & £3 (A § 8 -r> o -CL CO H CO -CL i i i i i i fff fff ggg cm sigSSS iilil j ; j 88t£SS l£||5 S8£8£t5£8S£SH j J 0.-0 O c.f» OO # n j 5JJ.

‘ID* n>» Q 0 (OKO •Q. (0 Hal (OMM O t Q q q - q ^>n) -

5.3.1 Overview

The 1995 drought imposed va huge additional workload on Water Resources staff, which unfortunately coincided with the peak period o f staff holiday leave. There was a marked increase in low flow field investigations, in general queries and complaints^ in abstraction restriction administration, in restriction compliance checks and in applications for new or varied licences.

Numerous watercourses dried up, particularly in the Teme and Worfe catchments in the Upper Severn area, and. in various brooks and drains in the Lower Trent lowland areas.

Abstraction- restrictions on licences linked to river flows were imposed earlier than usual, but were generally complied vwith.sThe late-imposition of restrictions in the Isle of Axholme ■■ (Lower Trent) aggravated the low flow problem. There was an increase in the number of licence breaches by* over-abstraction, and prosecutions were made during and following the drought period. . _

Navigation problems arose from low levels in the shallow gradient River Avon. Low flows in the upper Frome catchment were attributed to overabstraction in the neighbouring catchment by the local media, but tlie low flow situation was probably of natural origin.

There were , many instances where man’s influence exacerbated the effects of the drought. British Waterways licence-exempt abstraction for canal navigation from the River Swift further . reduced river flows. Drakelow Power Station pump rate variations in their River Trent abstraction caused short lived low flows, as did hydropower operations on the River Derwent.

The operation of river flow augmentation schemes was required in the Strine and Hadley Brook catchments in Upper Severn area. These schemes are designed to compensate for the reduction in river baseflows due to local groundwater abstractions.

5.3.2 Regionwide Issues

This section gives a flavour of the activities, events and problems faced by the Area Water Resources staff during the 1995 drought. Further information can be obtained from the area office incident files which contain details of all complaints and incidents investigated. '

The rainfall deficit began ,in mid March and flows rapidly fell throughout the Spring. Consequently, the Area Abstraction Control Rosters started earlier than usual: The summertime programme o f low flow current meter gauging surveys also began earlier and was more intense than usual.

The first flow-triggered abstraction restrictions were imposed on licensed abstractions in June. Some areas received requests from farmers to temporarily lift abstraction restrictions for short periods to allow irrigation when flows had naturally risen following rainfall. However, since restrictions are imposed and lifted by first class written notification, the flexibility of the restriction system is limited. Consequently, restrictions, once imposed, tended to remain in force throughout the summer.

1995 Drought Report Page 86 Environment Agency - Midlands Region The critical conditions and regionwide hosepipe ban led to many requests for new or varied licences, and many applicants were disappointed to find that an instant decision could not be made. Abstraction related enquiries increased following Severn Trent Water Ltd’s hosepipe ban on 22nd August. There may have been some cases where fanfiers deliberately unlawfully abstracted (either without a licence, or by exceeding their licence allocation), risking a substantial fine in order to irrigate their valuable crops. There were many enquiries and complaints about flood and trickle irrigation (which is licence exempt, unlike spray irrigation). Some farmers and landowners attempted to exploit the firefighting exemption, by asking if local brigades could fill their pools from local streams as part of a training exercise.

One of the main concerns in Area Water Resources Sections was the lack of staff resources to deal with all the additional work that a major drought entailed; The hot, dry weather and subsequent hosepipe ban led to : >

i) a significant increase, in. enquiriesi and.-complaints regarding abstractions and impoundments, many of which required field investigations. ii) an increase in the number of abstraction licences warned and restricted, requiring preparation of relevant paperwork and field visits to monitor compliance iii) an increase in the number of applications for new or amended licences

No contingency plans existed to meet this extra workload. Consequently, the water resource protection role was not fulfilled as well as it should have been. In the Upper Severn area,; whole catchments with restricted licences were unchecked due to the staff shortage, and this; negligence was noted by the fanning community.

Many staff had booked holidays during the summer period, straining the staff dealing with day to day incidents, enquiries, applications and restrictions. There was also a scarcity of managers when difficult decisions with huge commercial implications needed to be taken, particularly in Lower Trent area.

5.3.2 Upper Severn Area

Upper Severn Water Resources dealt with an average of 3 incidents per week requiring field investigations resulting from the hot, dry weather.

Numerous water courses in the Upper Severn area dried up, particularly the River Teme around Knighton, Stanage and Knucklas. The River Redlake at Bucknall,. the stream at Diddlebury, Ffhvddm Brook and Nedge Brook at Naird Lane are also known to have dried out. A spring near to Severn Trent Water Ltd’s Klnnerley borehole also dried up, and the cause of this is currently under investigation. Other rivers affected by low flows included the tributaries at the top of the River Worfe, the Worfe at Stableford, Cound Brook* River Kemp and Cwmdale Brook. Spray irrigation activity caused low flow problems in the Worfe catchment from Albrighton Brook to Wosley Brook, in Soul ton' Brook from Prees Heath to Wem, and in Shrawley Brook at Little Witley.

There were four prosecutions during the summer for non-compliance with licence conditions, and several subsequent prosecutions for over abstraction will follow.

1995 Drought Report Page 87 Environment Agency - Midlands Region The Welsh Water Ltd abstraction at Whitboume had to be restricted due to low flows for the first time. Severn Trent Water Ltd were required to compensate the Strine catchment for local groundwater abstractions with releases from the Edgmond borehole, also for the first time. Compensation to the Hadley Brook tributaries from Severn Trent Water Ltd’s Dunhampton borehole was also required as part of an Alleviation of Low Flows solution. Compensation requirements here reached the Stage Three level for the first time since the agreement was drawn up. The Strine and Hadley Brook compensation systems are described in Appendix 7.

5.3.3 Lower Severn Area

The Lower Severn area investigated 42 drought-related complaints in the summer period. Eight of these complaints were related to natural-Tow flows caused solely by the drought, but the majority were related to abstractions and impoundments (both legal, illegal and exempt). _

Low levels caused navigatioruproblemsin the Avon reaches below Bidford, causing the Avon Navigation Trust to raise objections to abstraction applications. Low flows on the Avon caused concern with the possibility of saline intrusion under high tides impacting on the water quality, and an Area Drought Committee was duly set up. However, no related negative effects were noted.

The British Waterways abstraction from the River Swift (the only local source) takes a significant portion of the natural river flow for navigation purposes in the Grand Union Canal, but is exempt from licensing. There were fewer complaints than normal regarding low flows , in the Swift, presumably because the public thought that the observed low flows were due to the drought. A Memorandum tif Understanding is being drawn up between the Environment Agency and British Waterways to relieve the problem.

Low flows were noted in the River Leam and there was only static water in the Gram Brook.; Low flows in the Glynch Brook, a tributary of the River Leadon, also caused concern. An exposed aquifer draws on the stream flow here, and investigations into possible compensation options are underway.

There were several complaints of low flows in the Upper Frame catchment. Local newspaper reports cast the blame on overabstraction from the neighbouring Thames region, but the low flows are more likely to have been caused by a combination of the drought, the exposed limestone fissures in the catchment and the loss o f the river's clay lining. The river levels on the River Frome varied considerably during the summer due to sluice gate adjustments related to old mill rights but, fortunately, no specific problems were encountered. .

Severn Trent Water Ltd overabstracted at several sources in the Area, and prosecutions may follow, although decisions have not yet been made.

1995 Drought Report Page 88 Environment Agency - Midlands Region 5.3.4 Upper Trent Area

Upper Trent Water Resources received an average of 5 complaints per week relating to low flow and abstraction problems over the summer period.

No major streams in the Area dried up, but some of the smaller tributaries and ditches were desiccated.

Sudden changes in the pump operation of the cooling water abstractions at Drakelow Power Station caused noticeable drops in river levels and generated complaints from anglers fishing below the Dove/Trent confluence. A working agreement between the Environment Agency and Powergen has been set up to alleviate future problems.

53.5 Lower Trent Area * Lower Trent Water Resources staff received few complaints regarding the low river flows, but there was concern that the duration of the low flows was much longer than normal, particularly on regulated rivers like the Derwent. There were only a few calls regarding dried up rivers where these are expected as the norm, for example, in the limestone dales in the , Peak District. However, several calls were received concerning low flows in Bondhay Dyke, a tributary to the River Ryton, which may have been partly attributable to unlawful abstraction and mining subsidence. The two Alleviation of Low Flows sites in the area (Dover Beck and Rainworth Water) attracted no more comment than in previous years. «

Streams known to have dried out or have been badly affected by the drought include Gallow Hole Dyke, Rainworth Water downstream of Rufford Lake, Bailey Brook and Heath End Brook upstream of Staunton Harold Reservoir. Low flows were also noted in the upper reaches of Langham Brook, Whissendine Brook, Gaddesby Brook,,Markfield; Brook and Thorpe Satchville Brook.

Groundwater levels were healthy at the start of the season and, held up well, and few groundwater-related complaints were received. A private groundwater supply at Cadeby near Market Bosworth dried up, but this was associated with a shallow perched water table. 3 • 'Flow restrictions were generally adhered to when applied to licences, but there were over 90 cases of overabstraction, considerably more than usual. There was some confusion amongst ' licence holders regarding the different types of licences (ie licences of right and those subject to a prescribed flow restriction) and the different threshold levels in force.

In the Isle of Axholme, some 25 abstraction licences are tied to environmental stress thresholds rather than numerical flow thresholds, and should have been imposed up to four weeks earlier. The late restrictions may have been responsible for the drying out of Hatfield Waste Drain over a considerable length. The delay in imposing restrictions on the Isle of Axholme licences was partly due to a scarcity of responsible managers during' the critical period.

There were three major incidents on the Derwent at the Belper Mill hydro-power site when the impoundment was emptied of about 150 Ml. These are detailed in the Derwent Dairy, Appendix 5 and Section 4.3.6. At the Borrowash hydropower site on the Derwent, low flows delayed tests required to determine generator operating rules. The braided river channels here are popular angling sites, and many complaints from the angling fraternity blamed the low flows, often unfairly, on uncontrolled operation of the hydropower plant.

1995 Drought Report Page 89 Environment Agency - Midlands Region 1995 Drought Report . Page 90 Environment Agency - Midlands Region CHAPTER 6 : OTHER IMPACTS OF THE DROUGHT

6.1 Introduction

This chapter covers the non water resources impacts of the drought, and includes a discussion of the effects on water quality, biology and fisheries. Other environmental' impacts are also briefly covered.

6.2 Overview of Water Quality. Biology and Fisheries

The drought of 1995 had both positive and negative effects on water quality, biology and fisheries. The rainfall deficit reduced the number of pollution incidents arising from runoff fiom roads and urban areas, storm water overflows and farm silage liquors. However, the prolonged low river flows limited the dilution of sewage effluents and other discharges, and reduced the submerged;habitats; Consequently,^improvements in chemical and biological quality were seen at some sites whilst deteriorations were observed elsewhere.

The main water quality effect of the drought was decreased dissolved oxygen concentrations. High ammonia was also a-problem,' particularly in rivers accepting high volumes of treated sewage effluent. Overall, however, the water quality in Severn and Trent catchments did not appear to suffer any serious adverse effects of the 1995 drought, and quality was generally better than in the 1989 drought. Ongoing improvements in the treatment o f sewage effluent aiid industrial discharges enabled the rivers to better tolerate the effects of reduced flows and; elevated temperatures.

The principal effect of the drought on biological quality was excessive plant, phytoplankton and algal growth (particularly blue-green algae and diatoms); The prolific growth was stimulated by enhanced nutrient, temperature and light levels, combined with slow current ' ’ velocities and windless conditions. Low river flows decreased effluent dilution and reduced submerged habitats, resulting in a decline in the numbers and diversity of invertebrates. '

Many watercourses dried up during the 1995 drought, particularly the upper reaches of the River Teme and River Worfe. Much of the established fauna and flora was affected, allowing the encroachment of other species, but natural recolonisation will limit the long term effects.

Many fish suffocated as warm temperatures and prolonged low river flows reduced di^olved , oxygen concentrations, and many NRA fish rescue operations were required. Major fish kills occurred when heavy thunderstorms followed six weeks of hot dry weather in early July. Storm water overflows and contaminated urban runoff entered watercourses already suffering , low dissolved oxygen levels. Fish life was obliterated in. stretches of the River Tame, and around 20,000 fish perished in the River Trent downstream. Around 16,500 fish fatalities also occurred on the Staffordshire and Worcester Canal as a result of the storms.

1995 Drought Report ' " Page 91 Environment Agency - Midlands Region Figure 6.1 : River Severn and Major Tributaries - Mean River Quality 1989 - 1995

Site ' Period BOD Ammonia Unionised PH -■ Chloride m m m Phosphate (ATU)5 Ammonia: i i i i i t mg/l mg/l mg/1 mg/l mg/l DegC i mg/l

MAIN RIVER SEVERN :

River Severn Summer 1995 1.1 0.02 <0.001 0.78 6.8 11 14.0 0.05 at . 1992-1994 1.3 0.03 <0.001 0.94 7.1 13 9.6 0.03 Caersws Summer 1989 0.7 0.02 <0.001 0.46 6.9 11 ' 12.8 0.04

"River Severn- _ Summer 1995 1.0 0.02 0.001 - 2.01 7.9 41 16.6 0.13 at 1992-1994 1.5 0.07 0.001 2.38 7.8 26 11.2 O.HT7 Shelton Summer 1989 1.0 0.08 0.002 1.80 7.9 39 15.6 0.13

River Severn Summer 1995 2.0 ’ 0.02 * 0.001 4.34 8.2 50 17.6 . 0.50 at 1992-1994 , 1.9 0.07 0.001 4.28 8.0 34 10.0 0.25 Bewdley Summer 1989 1.5 0.06 0.002 3.80 8.3 54 16.3 -

River Severn Summer 1995 2.1 0.10 0.003 6.21 8.0 112 16.6 1.08 at 1992-1994 2.3 0.09 0.002 5.04 8.0 53 11.0 0.50 W orcester"' Summer 1989 2.3 0.14 0.004 5.96 8.1 95 18.0 -

River Severn Summer 1995 2.3 , 0.17 0.005 6.12 8.0 88 16.3 1.00 at . 1992-1994 2.2 0.11 0.002 5.10 7.9 48 10.7 0.47 .. Upton Summer^I989 2.6 0.41 0.011 5.10 8.0 81 16.7 1.38

-River Severn Summer 1995 1.9' 0.11 0.004 6.90 8.1 96 , 17.1 1.37 at 1992-1994 2.1 0.11 0.002 . 6.14 8.0 50 10.8 0.66 Haw Bridge Summer 1989 2.1 0.30 0.009 6.20 8.0 89 17.1 2.20 RTVER SEVERN TRIBUTARIES • -

River Tern Summer 1995 1.3 0.08 . 0.003 8.90 8.1 69 16.1 0.70 at 1992-1994. 2.0 0.22 0.004 9.77 8.0 58 10.0 0.58 Atcham Summer 1989 1.3 0.09 0.002 . 7.63 8.0 54 16.0 1.13

River Stour Summer 1995 3.7 0.62 0.020 16.98 7.9 102 17.8 5.07 at 1992-1994 6.8 0.78. 0.012 ' 13.38 7.8 96 10.8 3.10 Stourport Summer 1989 5.5, 1.29 0.019 . 14.90 7.7 113 18.0 6.60

River Teme Summer 1995 1.5 0.03 r 0.001 3.65 8.3 32 16.8 0.29 at 1992-1994 1.7 0.05 0.001 4.98 8.2 26 10.4 0.15 Po\gick Summer 1989 2.0 0.13 0.003 4.10 8.0 32 12.0 -

River Avon Summer 1995 2.1 0.10 0.002 . 9.83 8.1 138 14.2 2.35 at 1992-1994 3.1 0.16 0.003 10.50. 8.1 68 10.9 1.53 Evesham Summer 1989 2.6 0.14 0.004 11.00 8.0 117 15.5 3.67

Dates: Summer 1995 1 June - 31 October 1995 1992-1994 1 January - 31 December 1992-1994 Summer 1989 1 June - 31 October 1989

1995 Drought Report Page 92 Environment Agency - Midlands Region Figure 6.2 : River Trent and Major Tributaries - Mean River Quality 1989 - 1995

Site Period BOD Ammonia Unionised Nitrate P« Chloride Temp Phosphate (ATU)s Ammonia: . '. mg/1 mg/1 mg/J mgfl D egC ' mg/1 ' MAIN RIVER TRENT -

River Trent Summer 1995 2.3 0.10 0.003 2.43 8.2 88 14.0 0.06 - at 1992-1994 2.9 0.36 0.007 4.44 8.0 85 11.0 0.62 Hanford Summer 1989 5.7 0.33 0.007 5.17 7.9 81 16.6 0.91

Rirer Trent Summer 1995 2.0 0.05 0.002 9.72 8.3 .121 17.8 1.93 at 1992-1994 2.9 0.17 0.003 9.18 8.1 130- U .9 1.12 Yoxall Summer 1989 2.5 0.09 - 0.002 - 8.45 8.2 161 16.9 2.12

River Trent Summer 1995 1.9 0.03 -0001 6.71 8.1 ■ 121 15.0 1.10 at 1992-1994 3.1 0.06 0.002 7.73 8.2 125 11.3 - Shardlow Summer 1989 2.3 0.06 0.002 5.10 8.0 149 -16.5 -

River Trent Summer 1995 2.5 0.14 0.005 9.17 8.1 154 17.2 2.38 at 1992-1994 3.0 0.22 0.004 8.48 8.0 101/ 11.7 1.20 Nottingham Summer 1989 4.0 0.24 0.005 8.57 8.0 120 17.4 2.72

River Trent Summer 1995 1.4 0.13 0.004 9.71 8.1 159 15.3 2.29 at 1992-1994 2.9 0.25 0.004 - 9.00 8.0 104 11.6 . 1.17 Dunham Summer 1989 3.4 0.37 0.009 9.04 7.8 145 18:2 2.59 RIVER TRENT TRIBUTARIES

River Sow Summer 1995 2.7 0.16- 0.004 9.24 8.0 125 15.8 1.74 at 1992-1994 2.7 0.22 0.004 9.06 7.9 128 10.9 1.01 Milford Summer 1989 3.2 0.29 0.006 8.04 ■ 7.8 138 15.2 : 2.01

River Tame Summer 1995 2.9 0.48 0.009 12.70 7.7 118 19.0 ' 3.85 at Chetwynd 1992-1994 , 4.4 1.00 0.011 - 12.00 7.6 99 . 11.9 2.30 Bridge Summer 1989 4.1 . 0.89 0.012 13.01 7.6 106 16.0 4.27

River Dove Summer 1995 1.7 0.03 0.001 3.94 8.4 49 18.2 0.51 at Monks 1992-1994 2.3 0.07 0.002 4.28 8.2 40 11.4 0.31 Bridge ’ Summer 1989 1.7 0.03 0.001 3.28 8.3 53 16.3 0.75

River Summer 1995 2.7 0.17 0.004 - 5.29 7.9 79 . 15.9 1.47 Derwent at 1992-1994 2.7 0.32 0.006 4.81 8.0 60 11.8 0.71 Ch. WUne Summer 1989 3.1 0.20 0.005 5.25 8.0 86 16.8 - 1.89

River Soar Summer 1995 1.7 0.14 ' 0.004 11.10 8.0 152 17.0 2.14 at Red 1992-1994 2.6 0.26 0.006 11.60 8.0 102 11.8 1.36 Hill Lock' Summer 1989 2.5 0.30 0.006 11.91 7.8 143 16.4 3.56

Dates: .. , V Summer 1995 1 June - 31 October 1995 1992-1994 1 January - 31 December 1992-1994 Summer 1989 1 June -31 October 1989

1995 Drought Report Page 93 Environment Agency - Midlands Region 6.3 Water Quality

Figures 6.1 and 6.2 tabulate average values of the principal water quality parameters for the Severn and Trent catchments, based on monthly sampling. The mean water quality during the summer of 1995 is compared with both the summer of 1989 and the three complete years from 1992 to 1994. In a typical summer period, with higher temperatures and reduced river flows, water quality might be expected to be worse than for the year asa whole.. Generally speaking, however, water quality during the summer of 1995 was better than-in 1989, and was often better than the previous three year mean due to recent improvements in discharge \ quality and increased in river self purification at the higher temperatures.

6.3.1 Biological Oxygen Demand i , *' , , The Biological .Oxygen Demand (BOD) indicates the level of organic pollution. In river self purification tends to reduce BOD with distance- downstream of the organic discharge point, and higher temperatures increase the recovery rate. In the Severn catchment, 1995 BOD values were similar or lower than the previous three-year average, and generally lower (better) than the 1989 values. In the Trent catchment, improved sewage treatment and in-river self purification in the higher temperatures pfoduced BOD concentrations consistently lower than the recent average and significantly (often 25 % or more) below the 1989 concentrations.

6.3.2 Ammonia

The ammonia concentration reflects the sewage effluent component of the river flow, and, like BOD,, is also subject to in-river purification. With reduced dilution in the. summer months, ammonia concentrations tend to rise in the summer, but this is counteracted. by enhanced self purification rates at die higher temperatures. Concentrations over the summer of 1995 were higher than die recent average downstream of Worcester on the River Severn. Elsewhere, however, concentrations were lower. 1995 figures were significantly better than 1989, reflecting the recent discharge improvements, with the River Stour at Stourport being about half the 1989 value. ' . /

Unionised ammonia is toxic to fish, and higher temperatures and pH values tend to raise the concentration! On the whole, the unionised ammonia concentration was greater than the recent. mean in the Severn catchment, but lower in the Trent catchment. Summertime concentrations were significantly lower in 1995 than in 1989. However, unionised ammonia concentrations approached the EC Fisheries standard of 0.025 mg/1 on the River Stour at'Stourport, despite the reduction in ammonia concentration.

6.3.3 Nitrate

Nitrate concentrations were generally higher in 1995 than in 1989, reflecting the lower river flows and high temperatures, which increased the rate of oxidisation of ammonia to nitrite and nitrate. High nitrate concentrations can pose a problem for industrial abstractors.

6.3.4 pH

The high temperatures and many hours of sunshine in 1995 intensified photosynthetic activity, producing slightly elevated pH levels throughout much of the Region.

1995 Drought Report Page 94 Environment Agency - Midlands Region f t 6.3.5 Chloride

Chloride usually originates from sewage and its concentration is therefore elevated in drought conditions when lower flows reduce dilution. High concentrations can cause significant problems for industrial abstractors. The 1995 drought led to chloride concentrations significantly higher than the recent mean, with levels doubled on the Avon at Evesham. The 1995 concentrations were generally worse than in 1989 throughout the Severn catchment and in the lower parts of the Trent basin, reflecting the more severe drought in terms of prolonged low summer flows. Exceptions to this rule were the River Erewash, probably reflecting the reduced pumping of minewaters, and the River Derwent, reflecting the ; enhanced river flows from the Carsington Reservoir regulation releases.

6.3.6 Phosphate

Phosphate levels: were higher in -the summer ofel995.than the mean of the previous three years, reflecting the increased proportion of effluent tojhatural river flow. Levels were lower than in 1989, however, despite the prolonged low river flows, partly due to improved sewage treatment works performance in recent years.

6.3.7 Temperature

The summertime water temperatures in 1995 were similar to those observed in 1989. Lowest. average temperatures occurred in the upland reaches of the catchments, while the urban River . Tame catchment was the warmest; High water temperatures reduce the effectiveness of industrial cooling water abstractions. Returned power station cooling waters have a significant. impact on river water temperature, especially on the Lower River Trent.

6.3.8 Continuous Water Quality Monitors

The network of 24 water quality monitors, strategically placed throughout the region, continuously measure up to eight parameters at .15 minute intervals. The monitors provide a useful picture of the effects of the 1995 drought on water quality in the Midlands.

Data from these stations highlighted low dissolved oxygen levels as the main effect of the drought, although high ammonia was also a problem particularly in rivers accepting high volumes of treated sewage effluent. Low flows increased water quality problems in urban rivers such as the Erewash, Sowe and Tame. Details of the Tame storm-pollution event are given separately in Section 6.5. Large rivers such as the Trent and Avon which maintain good fisheries also suffered quality problems as a result of inputs from poor quality tributaries.

Figure 6.3 shows the DO and ammonia at;three contrasting sites for a 10 day period in August 1995 :

The River Sowe at Stoneleigh - an urban river, just downstream o f a major treated sewage effluent discharge The Avon at Rockmill - downstream of the confluence of the River Sowe The River Derwent - a comparatively clean rural river

1995 Drought Report Page 95 Environment Agency - Midlands Region Dissolved Oxygen % Saturation Dissolved Oxygen % Saturation Dissolved Oxygen % Saturation 40 40 70 - - Figure 6.3 : 1995 Dissolved Oxygen and AmmoniaConcentrationsand Oxygen Dissolved 1995 : 6.3 Figure ie oea Stoneleighat River Sowe River Avon at Rockmill Riverat Avon Urban, D/S effluent discharge effluent D/S Urban, D/S River Sowe confluence D/SRiver Sowe Dissolved Oxygen Ammonia 6.4 Biological Quality

, As with water quality, there are conflicting positive and negative effects of a drought on biological quality. Local biological quality observations are given below. Biological quality is generally expressed in terms of a ’biological score’. Unpolluted sites with a wide range of species score higher than poor quality sites with restricted diversity.

6.4.1 Upper Severn Area .

The quality of the Blakedown Brook deteriorated in 1995 due to insufficient dilution of sewage effluent. Low flows in the Afon Cerist restricted dilution of the Afon Trannon waters (Severn tributary upstream of Newtown), resulting in poorer quality at Camedd.

The overall effect of low flows on these watercourses was a reduction in the number and diversity of invertebrates, resulting in biological scores akthe lower end of their usual range.

6.4.2 Lower Severn Area

In the Avon catchment, increased growth of macrophytes (aquatic plants) were the most common problems, particularly in the Bow Brook, Ripple Brook and River Stour. Early Spring growth of diatoms (microscopic silica-based algae) was more apparent in 1995 than in previous years. Floating diatom mats were visible on slow flowing lowland watercourses, , and thick benthic (river bed) growths were reported. Algae affected public water supply, abstractions at Strensham and Mythe during April.

There was a substantial increase in the number of watercourses where blue green algae were identified, particularly floating mats of Oscillatoria. Nearly all the tributaries on the south side v of the Avon supported these growths both in rural and in urban areas. Oscillatoria mats are commonplace in the Scottish iochs characterised by low phosphorus concentrations and low velocity waters, and similar conditions arose during the drought o n the River Avon tributaries draining the Cotswolds. This led to an extensive public awareness campaign involving the media, District Health Authorities, local councils and the Ministry of Agriculture, Food and Fisheries.

6.4.3 Upper Trent Area

The impact of low flows on biological quality in the Upper Trent area was generally found to be less than in 1989. The River Sence, River Tean, River Penk, River Sow and Black Brook have high effluent components but recent substantial investments in sewage treatment have made a considerable difference. Larger, cleaner rivers, such as the Dove, did not show a detrimental effect of the 1995 drought.

The deoxygenation of the River Tame during the July storm evSent (detailed in Section 6.5) reduced biological scores in the Tame and Trent, but they had recovered by the Autumn. Blue green algae from Cop Mere affected the River Sow for several miles, although this is probably an annual occurrence.

1995 Drought Report Page 97 Environment Agency - Midlands Region 6.4.4 Lower Trent Area * Biological quality improved in some Lower Trent watercourses but deteriorated in others. The dry weather reduced urban run-off and storm sewer overflows, so watercourses draining .urban areas, such as the River Leen, tended to benefit.

Biological scores on the River Erewash and Leen were better following the drought in the Autumn of 1995 than in the previous Spring, due to reduction in storm overflows, improved sewage treatment and increased in-river self-purification. In the Wreake catchment, however, Autumn scores were lower, associated with the loss of submerged habitat and lower effluent dilution. ~

AIgae significantly affected the quality of water in Ogston Reservoir, and transfers of water from Carsington to Ogston Treatment Works were used in preference for public water supply early in the season/

The low water levels or drying out of the drains in the Isle of Axholme led to a decline in rare species, and invasion by nuisance plants of low ecological value. In particular, a 7 Km stretch of the Hatfield Waste Drain dried out in the summer. This is a site of local importance for Whorled Water Milfoil, but ecologists hope that the species will recover as water levels rise. The drains became dominated by species such as blanket algae and the invasive Australian Swamp Stonecrop.

1995 Drought Report Page 98 Environment Agency - Midlands Region 6.5 Fisheries

6.5.1 Impact of Low River Flows on Fisheries

The 1995 drought gave rise to the worst prolonged low flow conditions since the 1976 drought in some of the Region’s rivers. The River Teme was particularly badly affected, and many miles of the upper reaches ancf parts of several tributaries dried up completely. A large number of trout were rescued when the Teme was reduced to a series of rapidly drying out pools. Many of these fish were of exceptional quality, including some specimens weighing up to 31bs. The fish were dye-marked prior to being released further downstream, to facilitate studies on the recolonisation of the reaches that dried out in 1995.

Where river flow had been maintained throughout the summer, electric fishing surveys revealed no major impacts on salmon spawning streams. Although some individual sites contained fewer salmons and trout than, had ^previously, been found, there was no overall decline. Preliminary observations indicate that spawning has been good, in both flowing and still waters.

River regulation helped to maintain flows in rivers such as the Severn and Derwent, and coarse fish populations in regulated rivers were not affected significantly by the 1995 drought. Coarse angling was also good, as is usual in warm summers.

Unregulated lowland rivers such as the Worfe and Perry suffered considerably, however, with' anticipated impacts on both coarse and game fish. Angling was also adversely affected.

Fortunately, the high water temperatures did not appear to have adversely affected grayling stocks (a species of Arctic origin), which suffered in the 1976 drought.

6.5.2 Effect of the Drought

The low flows and high temperatures produced low dissolved oxygen concentrations causing distress to fish in both still and flowing waters, and many NRA fish rescue operations were required. Despite the major rescue attempts, widespread fish mortalities occurred across the region during the summer, as a direct or indirect result of the weather. Algal blooms and low. river flows exacerbated the problem.

Figure 6.4 graphically shows the monthly distribution of reported fish mortality incidents throughout the Region in 1995. Of the 265 incidents, more than one third were directly or indirectly due to the prevailing climatic conditions.

1995 Drought Report Page 99 Environment Agency - Midlands Region Figure 6.4: Reported Fish Mortality Incidents 1995

8 0

0) c 60 0) "O IM o c

"O 0) r 40 o a 0) O'

o 2 0 ------z

0

Jan 95 Feb 95 Mar 95 Apr 95 May 95 Jun 95 Jui 95 Aug 95 Sep 95 Oct 95 Nov 95 Dec 95

8 Weather Related H 0 0 1 . 1 *. :3 - ■ 4 4 2 3 7 3 0 • 0

Other Incidents H 1 5 5 3 2 38 , 19 27 15 11 12 7 3

TOTAL 1 5 6 33 . 41 27 71 ' 38 18 . 15 7 3

Y 6.5.3 Storm Incidents

Summer storms following periods of dry weather can cause catastrophic pollution and resultant fish kills, either through sewage treatment works storm water overflows or through the flushing out of accumulated urban pollution. \ The Tame storm event in July was one of the worst fish mortality incidents ever experienced in this Region, and is detailed separately in Section 6.5. Also badly affected was the Staffordshire & Worcester Canal from Tettenhall to Dimmingsdale. Over 4000 dead roach, perch, bream and gudgeon were counted following a storm overflow from Bamhurst STW during the severe thunderstorms in early July, however, post-pollution survey work suggested the total kill was closer to 16500. Some fish were rescued and transferred to an adjacent clean stretch. Fish mortalities also occurred in the Leen, Erewash, Fairholme Brook and Soar in early July, but aeration equipment proved effective in the Soar.

Following the fish kills and rescues, the NRA initiated an extensive restocking programme.

6.5.4 Other Effects on Fisheries in 1995

While river levels were low during the drought, many riparian landowners took the opportunity to carry out river channel works for both anti-erosion and gravel extraction purposes. This posed a threat of damage to important salmon spawning grounds especially on the Afon Gam and River Tanat in the Upper Severn area. Fortunately, these fears have • proved unfounded, and large numbers of salmon .have spawned in even the worst affected areas. •

Crayfish in some tributaries of the Teme were eliminated in some areas by outbreaks of crayfish plague. Although not directly caused by the drought, the low flows and high temperatures may well have exacerbated the situation.

1995 Drought Report Page 101 Environment Agency - Midlands Region 6.6 River Tame Incident - July 1995

The drought was an important factor in a major pollution event on the River Tame in July 1995. y

Hotj dry weather had reigned for 6 weeks, causing low river flows and reduced dissolved oxygen concentrations. A number of localised thunderstorms around the 10th July, mainly in southern Birmingham, scoured sewers, drains and contaminated areas. This resulted in large volumes of polluted surface run-off suddenly entering the Tame. As flows rose sharply, there was a corresponding rapid fall in Dissolved Oxygen (DO) concentrations, which unfortunately coincided with the minimum DO concentration in the normal daily cycle. The pollution load almost instantaneously completely deoxygenated reaches of the River Tame, and increased ammonia levels. The effect of the polluted water as it passed the water quality monitor at Water Orton on the River Tame, upstream of Lea Marston Purification Lakes, is shown in Figure 6.5.

Retention in the purification lakes had only a limited effect on the downstream dissolved oxygen concentrations, and very low levels were recorded all along the Tame to its confluence with the River Trent, resulting in a major fish kill in the stretch downstream of the lakes. Aeration devices were deployed immediately by NRA staff on the lower Tame, but had limited impact. Subsequent fishing surveys revealed a 97% loss of fish.;

There, was also an adverse effect on the River Trent, with the minimum DO concentration being recorded at Burton-on-Trent, 10 Km downstream of the Tame confluence. A combination of emergency actions were taken to protect the River Trent fishery :

Oxygen was injected into the river at Drakelow Power Station near Burton-on-Trent using a Vitox oxygenator borrowed from Anglian Region. One tonne of liquid oxygen was injected into the river each day for five days, until oxygen levels returned to normal. Water was circulated through power station cooling towers by pumps to increase oxygen concentrations on route. Severn Trent Water Ltd assisted by ceasing their abstraction from the dean River Dove, thereby maximising the downstream input of clean, oxygen-rich waters.

These endeavours undoubtedly saved thousands of fish, but could not prevent a major fish kill, and an estimated 20,000 fish were lost in the River Trent around Burton.

- Biological scores in the Tame and Trent were also reduced, but had mostly recovered by the Autumn. The NRA undertook to ameliorate the impact by initiating an extensive restocking programme. Over 100,000 fish were introduced to the Trent and Tame during October and November.

Shortly after the fish kill in the Tame and Trent, thousands of coarse fish in the River Cole (a Tame tributary) were killed, due to overflows from storm drains. Subsequent surveys on ' 19 July indicated the obliteration of fish life from upstream of Coleshill Hospital to the confluence of the Blythe. The recolonisation of the affected stretches will be monitored.

The Tame event highlighted the vulnerability of rivers to pollution events during drought conditions. Following the incident, there has been comprehensive investigations to determine what actions can be taken to reduce the impact of a similar incident in the future, such as the possible use of hydrogen peroxide as an emergency source of oxygen.

1995 Drought Report Page 102 Environment Agency - Midlands Region . Dissolved Oxygen % Saturation -uy -uy -uy -uy -uy 0Jl 11-July 10-July 9-July 8-July 7-July 6-July 5-July Figure 6.5 : Dissolved Oxygen & Ammonia at Water Orton on the River Tame River the on Orton Water at Ammonia & Oxygen Dissolved : 6.5 Figure Dissolved Oxygen Date (1995) Date Ammonia 2Jl ' 3Jl 14-July 13-July ' 12-July 15-July k - / 3 - - 4 - 2 1 Ammonia mg/l 6.7 Other Environmental Effects of the Drought

One positive effect of the drought was that the rainfall deficit greatly reduced leachate production at many landfill sites.

Reductions in output from some water treatment works to conserve reservoir storage, such as Bamford (Derwent Valley Reservoirs), produced a corresponding reduction in sludge production and disposal requirements. However, these were localised reductions, and sludge production at other works, such as those running at maximum output to meet the exceptional demands, would have risen. '

Higher than average ambient temperatures and lack of cleansing rainfall contributed to poor air quality, including enhanced levels o f low level ozone. Dispersion of pollutants was slower in the settled windless conditions. With many people spending more time than usual out of doors, there was an increase in air quality complaints ^particularly around built up areas close to industrial premises. "

There was a greater than normal requirement for dust suppression water spraying activities due to the prolonged periods of dry windless weather. Some Waste Regulation licence - conditions regarding tip spraying frequencies could not be met due to the unavailability of suitable water supplies, and this created problems close to built up areas. In at least one case, operators had to resort to tankering in all the water required. Similar problems with dust suppression were experienced on major industrial sites subject to Integrated Pollution Control. Authorisations.

1995 Drought Report Page 104 Environment Agency - Midlands Region CHAPTER 7 : FURTHER INFORMATION

7.1 Further Reading

7.1.1 1995/1996 Regional NRA / Environment Agency Reports

Hydrometric Report and Catalogue 1995 prepared by Regional Hydrometric Data Team due August 1996 Low Flow Data For Severn Trent Region 1975-1995 prepared by Regional Hydrometric Data Team . . in preparation . Operation of the Shropshire Groundwater Scheme in 1995 prepared by Regional Groundwater Team in preparation Effect of the 1995 Drought in Lower Trent Area (internal memorandum) prepared by Lower Trent Water Resources Team c/o Roger James May 1996

7.1.2 1995/1996 National NRA / Environment Agency Reports

Series of Drought Reports to the Secretary of State For the Environment 1 : The Drought of 1995 August 1995 2 : Measures to Safeguard Public Water Supplies December 1995' 3 : Refill Prospects February 1996 4 : Review'of Water Company Plans to Safeguard Summer Water Supplies May 1996

7.1.4 Previous Regional Drought Reports

The Drought of 1975 April 1976 Regulation of the River Severn 1975 and 1976 December 1977 The 1984 Drought - A Perspective and Comparison 1985 1989 Drought Report in preparation

7.1.3 External Reports

Assessment of Drought Severity British Hydrological Society Occasional Paper No. 3 March 1994

1995 Drought Report Page 105 Environment Agency - Midlands Region 7.2 Acknowledgements

This report had been prepared by Rachel Spence of the Water Resources Section at the headquarters of the Midlands Region. Many thanks to all those who provided contributions, help and assistance, in particular :

Environment Agency

Technical Advice and. Proof Reading Gordon Davies, Tim Harrison, Jim Waters Water Quality and Biology Dave Brewin, Shelley Howard and Teams Fisheries and Conservation Paul Lidgett and Area staff Local Water Resource Problems i Upper'Severn Jean Payn and Team Lower Severn Derek Taylor and Team Upper Trent Ivy Dolby and Team Lower Trent Roger James and Team

External.

Operational Activity Water Supply Services Group, Severn Trent Water Ltd headquarters, Birmingham Air Temperature John Kings, School of Geography, University of Birmingham

1995 Drought Report Page 106 Environment Agency - Midlands Region APPENDIX 1 Figure A 1.1 Ordinary Drought Orders 1995

Ordinary Drought Order General Effect of Drought Order Other Conditions Agreed with the Water Companies Promoted Statutory Instrument No, (London Dates In Force Gazette)

The Severn Trent Water i) To reduce the minimum compensation as measured at Solomon’s i) Overridden if Tittesworth Reservoir 95%'full. 14/12/95 Ltd (Tittesworth) Hollow from 14.8 to 5.0 Ml/d to conserve Tittesworth Reservoir ii) NRA can override on water quality grounds. (Drought) Order 1995 .resources for supply. iii) STW to provide daily 5-parameter chemical analysis of No. 3441 ii) To substitute reduced reservoir compensation with downstream water abstracted from Tittesworth Reservoir if storage falls compensation from Abbey Green (up to 10 Ml/d) and Deep Hayes below 20%. 29/12/95 - 29/06/95 (up to 4.5 Ml/d)'boreholes and the new Wakefield Well (up to 2.0 (6 months) Ml/d) such that total compensation releases from the Tittesworth/Leek scheme is reduced from 19.3 to 18.0 Ml/d. .

The Severn Trent Water i) To reduce the minimum compensation to the Rivers Derwent and i) Overridden if Derwent Valley Reservoirs 95% full. 14/12/95 Ltd (Derwent Valley) Noe from 54 to 34 Ml/d and from 17 to 12 Ml/d respectively, with ii) NRA can override on water quality or shallow river depth (Drought) Order 1995 the combined minimum compensation reduced from 74 to 51 Ml/d grounds No. 122 to conserve the reservoirs’ resources for supply, iii) STW to.finance study on effects of reduced compensation on ecology, and pay for any mitigation works. 19/01/96 - 18/04/96 (3 months) /

The Severn Trent Water i) To reduce the prescribed flow at the Derby gauging station from i) Overridden if Carsington Reservoir 85% full. 14/12/95 Ltd (Ambergate) 680 to 500 Ml/d to allow additional abstractions from the River ii) NRA can override on water quality grounds. (Drought) Order 1995 Derwent at A mbergate for refi 11 of Carsington or Ogston iii) STW to install 7-parameter interTOgable water quality No. 121 Reservoirs: monitor upstream of Courtaulds abstraction in Derby. iv)* STW to finance study on effects of reduced flow on 19/01/96 - 18/04/96 fisheries, and pay for any restocking. (3 months)

The North West Water i) To'reduce the minimum compensation to the Afon Vymwy from i) Overridden if Lake Vymwy drawdown less than 1.5m 26/02/96 Ltd (Lake Vyrnwy)- 45 to 25 Ml/d to conserve Lake. Vymwy resources for supply. (88.8% full).’ (Drought) Order 1996 ii) No gains to the NRA Severn Trent Region Water Bank will ii) NRA can override if risk of damage to aquatic No. 806 arise from the Drought Order compensation reduction. environment. iii) NWW to finance study on. environmental effects of 16/03/96 - 15/06/96 Drought Order, and pay for any mitigating measures (3 months) includihg restocking of salmon or trout. 1995 Drought Report Page A 2 Environment Agency - Midlands Region »

APPENDIX 2 : DESCRIPTION OF THE RIVER SEVERN REGULATION SYSTEM

A2.1 Aims of the River Severn Regulation System

The aim of the River Severn Regulation System is to ensure that there is sufficient flow in the river to satisfy the demands of the major abstractors on the Severn and to meet environmental needs. Controlled releases from regulation sources help to provide sufficient fresh water flow in the river to allow adequate dilution of sewage effluents, to keep the, fisheries and other aquatic life in a healthy state, and to prevent saline tidal water encroaching up the estuary to fresh water abstraction points. At the same time, available regulation resources must be used scarcely and wisely to ensure that support can be maintained throughout the season, and to avoid unnecessary costs. The system is operated under a Section 20 (Water Resources Act 1991) Operating Agreement. 1

The locations of the principal components of the River Severn Regulation System are shown on Figure A2.I. The flow at Bewdley, just upstream of the Stour confluence half way down the Severn, is the control point of the Regulation System. Bewdley 5-day mean flows are maintained at 850 Ml/d, with a minimum allowable mean daily flow of 650 Ml/d. These flows have been selected to ensure that the abstraction, dilution and environmental requirements in the river are met, without excessive wastage of resources.

A2.2 Resource Components of the River Severn Regulation System * * There are three support components to the River Severn Regulation Scheme. Llyn Clywedog provides the bulk of the regulation releases, with further resources available from Lake Vymwy and the Shropshire Groundwater Scheme.

Llyn Clywedog Clywedog Reservoir was built specifically for regulation purposes in the late I960’s. Of the three regulation resource components, it has the largest available volume, typically over 40000 Ml per season if the reservoir refilled the previous winter. It also has the largest flow rate of up to 500 Ml/d for regulation purposes. It is the most versatile resource with a variety of fixed and variable release valves instantly adjustable from the 24-hour control room.

Llyn Clywedog Control Curves have been drawn to assist with the management of the reservoir resources, relating recommended regulation actions to the reservoir storage and the time of year. These curves control flood drawdown and hydro-electric power releases, and recommend when to use the Shropshire Groundwater boreholes or when to seek a Drought Order from the Secretary of State for the Environment.

Lake Vyrnwy Limited resources from Lake Vymwy are also available, but North West Water Ltd use much of the reservoir’s resources for direct supply. Since 1979, a water banking system has been used for Severn Regulation purposes. A fixed volume of 725 Ml per month between March and October is allocated for regulation releases, and can be accumulated until required. This allowance gives a sustainable output of just 25 Ml/d over the normal 45 Ml/d compensation rate, although the release can be much higher for short periods (up to 405 Ml/d). Additionally, when natural river flows are high following rain, the compensation requirement from the dam is reduced and the saved compensation release (20 Ml per day) can also be added to the Vymwy Water Bank. Reduced compensation is allowed whenever the 9am flow on the River. Cownwy at Cownwy Weir (a diverted inflow stream) are above 20 Ml/d.

1995 Drought Report Page A3 Environment Agency - Midlands Region Any regulation releases from the reservoir are deductible from the water bank. Other releases made for fisheries purposes or environmental quality reasons are also deductible, such as freshet releases to dilute a pollution or to increase estuary flows during high spring tide periods to prevent encroachment of saline water up river. Flood drawdown releases and overflows are also deductible from the bank, such that any bank resources remaining at the end of the summer are usually eliminated over the following winter.

Lake Vymwy releases are less controllable than Clywedog reservoir releases. There are only two outlets in addition to the. smaller compensation and hydro-electric power outlet. The valves are manually roughly adjusted, and when the flow has settled after a few hours the valve setting is fine tuned. The reservoir is not manned after 4pm or at weekends under normal circumstances.

Shropshire Groundwater Scheme The purpose built Shropshire Groundwater Scheme is the least flexible and most expensive support component in the Severn Regulation scheme, and is used when forecasts suggest that the available Clywedog and Vymwy resources may not be sufficient to last a severe or extended drought season, in contrast to the gravity-controlled reservoir releases, groundwater has to be pumped at considerable expense, amounting to around £1300 a day for Phases 1 and II, and there are significant staff resource implications in monitoring groundwater levels, soil moisture and water quality once operation commences. Field visits by staff based at. Shrewsbury are required to turn the boreholes on, so a few days warning is normally given. ^ However, the boreholes can be instantly turned off remotely. In order that the groundwater drawdown and recovery rates can be measured when the boreholes are switched on or off, changes should ideally be spaced at least a week apart.

The Shropshire Groundwater Scheme currently (early 1996) has a net output of only 85 Ml/d, so the Clywedog control curves recommending the use of the boreholes have been constructed to encourage early, sustained use of this limited output resource to conserve reservoir storage. This strategy ensures that the available resources can provide continued support should the Regulation Season become prolonged. ~

Two Phases of the Shropshire Groundwater Scheme are cun-ently available, although a smaller Phase 111 (over the Leaton area to the North o f Shrewsbury) will be commissioned late in the summer of 1996. Phase I, over the River Tern catchment, consists of 8 boreholes with a combined net output of approx 40 Ml/d. Phase II consists of 10 boreholes draining to the River Perry catchment or to the River Severn, just upstream of the Perry confluence, with a net output of approximately 45 Ml/d. The gross pumping rate on each borehole is individually logged and archived, and the net output is estimated at 85% of gross output to allow for pipeline losses and reduced river flows caused by the reduced natural groundwater support. The yearly licence for Phases I and II is sufficient to allow maximum pumping throughout a prolonged Regulation Season, but the rolling five year licensed volume of little more than twice the annual volume may constrain operation during consecutive drought years.

1995 Drought Report Page A4 Environment Agency - Midlands Region Figure A2.1 THE RIVER SEVERN WATER RESOURCES/SUPPLY SYSTEM

To Liverpool

Shropshire Groundwater Scheme

Wolverhampton & South Staffs

Coventry

• Bristol A2.3 Main Severn Abstractions Upstream of Bewdlev

There are four principal main-river abstractors upstream of Bewdley whose net abstractions are allowed for in the Severn Regulation spreadsheet modelling, comprising three major public water supply abstractions and one industrial user. The abstraction locations are illustrated on Figure A4.1 and the licence conditions are tabulated on Figures A4.2 and A4.3. In addition, agricultural spray irrigation licences have a significant impact on river flows.

Iron bridge Power Station lronbridgei Power Station is the largest industrial abstraction on the Severn, with large quantities abstracted for cooling and circulation. However, much of the water is returned immediately downstream, with net abstractions averaging 15 Ml/d in the summer (1995).

Shelton The public water supply abstraction at Shelton, Shrewsbury is the smallest of the three, with gross abstraction averaging 15 Ml/d throughout the summer (1995), but approximately three quarters is returned through downstream sewage works.

Hampton Loade Hampton Loade is the principal public water supply abstraction on the Severn^ just downstream of Bridgnorth. The abstraction is operated by South Staffordshire Water Ltd (SSW), although Severn Trent Water Ltd (STW) are entitled to a portion of the treated water from this source through a complex joint licence arrangement. SSW retain about two-thirds; of the abstraction for their own use. None of this water is returned upstream of Bewdley although some 20% is returned via sewage works to the River Stour, confluencing with the Severn just downstream of Bewdley. All the abstracted water (averaging 180 Ml/d in the summer of 1995) is pumped to Chelmarsh Bankside Storage Reservoir nearby.

SSW normally try to keep the bankside storage topped up to a capacity of 3050 Ml throughout the summer for maximum security of supplies. The bankside storage can then be drawn down whenever abstraction from the Severn has to cease due to a pollution incident. It is also used to balance the variations in demands at the water treatment works, and to utilise off peak ‘ electricity tariffs for pumping. This cyclic variation in pumping rates causes large overnight falls in the observed flows at Bewdley.

When major storms affect the catchment, the river water quality is often severely-reduced by increased turbidity, preventing abstraction, so that the storm runoff' becomes a pollution incident. From the point of view of River Severn Regulation, this is unfortunate since the surplus natural flows in the river are not utilised and the bankside storage is drawn down while the ’pollution’ travels past the inlet. Once the storm flows have passed by and Regulation releases recommence, additional abstractions to top up the reservoir are required.

Trimpley Severn Trent Water Ltd’s public water supply abstraction at Trimpley, downstream of Hampton Loade, also represents a net loss to the Severn upstream of Bewdley. Trimpley bankside storage reservoir has a capacity of just 936 Ml. Pumping rates are less variable throughout the day, averaging 60 Ml/d in the summer o f 1995.

/ 995 Drought Report P age A 6 Environment Agency - Midlands Region As well as supplying local communities, recent improvements in the treatment capacity of the works at Trimpley and the associated pipeline links allows the Trimpley treated water to supply North Worcester. These improvements were completed in June 1995 jn advance of the closure of the Worcester Barboume abstraction and treatment works further downstream. Raw water from the Trimpley abstraction can also be pumped to the Elan Valley Aqueduct when required. This backs up the existing transfers from the Elan Valley Reservoirs to Frankley treatment works, used to provide Birmingham’s supplies, and is used when the storage at the Elan Valley Reservoirs is critically low or when demands are exceptionally high.

The Hampton Loade and Trimpley licences are tied with joint maxima, as tabulated on Figure A2.2, so that they must agree a strategy between them if SSW want to take over 220 Ml per day at Hampton Loade. In addition to the singular and tied hourly, daily and annual licensed quantities, there are further constraints on total volumes abstracted over the first 100 regulation days. Early season pumping at high rates within the daily maxima may have to be curtailed later in the season when there is a possibility of reaching 100 Regulation Days.

Spray Irrigation Surface water spray irrigation abstractions upstream of Bewdley can have a significant impact on flows in the Severn’ There are about 360 spray irrigation licences upstream of Bewdley. Over one third of these licences are conditional on adequate prevailing river flows, and can be prevented from abstractirig by written notification from the Environment Agency when flows fall. Average spray irrigation abstractions upstream of Bewdley assuming a 60 day irrigation season are likely to be around 70 Ml/d (1995). ♦ .

1995 Drought Report Page A7 Environment Agency - Midlands Region Figure A2.2 : 1995 HAMPTON LOADE AND TRIMPLEY ABSTRACTION MAXIMA (according to special conditions in force during 1995)

110 = STW at Trimplcy SINGLECOMBINED >63 » STW & SSW at Hampton Loade 110+163 584 = SSW at Hampton Loade no 163 584 110+163 163 + 584 + 584

Max Reg’n 8,833 m3 $ (Notified) N/A N/A N/A N/A Eq.ratc 212 Ml/d N/A (584/10). Bewdley < 1100 Ml/d (without 11,700 mJ £ notification of Eq.rate 281 Ml/d N/A N/A N/A ' n/a (584/9) N/A Max Reg’n) A. Linear increase HOURLY in hourly max from I3.333mj Bewdley between (Eq.ratc 320Ml/d) 1100 and 2000 to 17,100m1 Ml/d N/A N/A N/A N/A (Eq.rate 4 lOMI/d) N/A with increasing Bcwdley flow (584/8) 17,100 m J Bewdley > 2000 Eq.raie 410 Ml/d N/A N/A . N/A N/A N/A Ml/d (584/7)

60,000 mJ 182,000 m1 30,000 m* 242,000 m3 212,000 m J 272,000 mi Max Reg’n = 60 Ml/d = 182 Ml/d = 30 Ml/d = 242 Ml/d = 212 Ml/d = 272 Ml/d fIJO/2c.I63/2d) (110/2c,163/2d) (584/6)

220,000 mJ # 280,000 mi Bewdley < 1100 180,000 m* 90,000mi 400,000 mJ 400,000 mJ = 280 Ml/d Ml/d = 180 Ml/d = 220 Ml/d = 90 Ml/d = 400 Ml/d = 400 Ml/d (110/2a, 163/2a) (584/5)

DAILY 400,000 mi ti 320,000 mJ 180,000 m’ 320,000 mJ 90,000 mi 400,000 mJ April - October ft .= 320 Ml/d <4 = 180 Ml/d = 90 Ml/d = 400 Ml/d = 400 Ml/d = 320 Ml/d (584/4) At all other ff 180,000 mJ ft 320,000 mJ # 90,000 mJ # 400,000 mi # 400,000 mJ tt times when above 400,000 m* ft = 180 Ml/d . = 320 Ml/d = 400 Ml/d = 400 Ml/d daily conditions do = 90 Ml/d = 400 Ml/d (I10/2a.l63/2a) (163/2b) (584/-) (llOn. 163/2) (584/3) not apply

First 100 days of 6,000,000 mJ 18,200,000 mJ 3,000,000 m1 24,200,000 m1 21,200,000 mJ 27,200,000 m1 Eq.ratc 60 Ml/d Eq.ratc 182 Ml/d Eq.ratc 30 Ml/d Reg’n (pro-rata for Eq.raie 242 Ml/d Eq.rate 212 Ml/d Eq.rate 272 Ml/d extra days reg'n) 01012b. I63/2c) (110/2b.l63/2c) (584/2) 7,866,000 m1 SEASON April - October Eq.ratc 43 Ml/d N/A N/A N/A N/A N/A (584/1) November - 11,490,000 m1 Eq.rate 63 Ml/d March N/A N/A N/A N/A N/A (584/1)

22.000,000 mJ* 66.430,000 17,505.000 m1* 88,430,000 mJ * 83,935,000 m1 * 105,935,00001’* a n n u a l Annual * Eq.ratc 60 Ml/d Eq.ratc 182 Ml/d Eq.ratc 48 Ml/d Eq.rate 242 Ml/d Eq.raie 230 Ml/d Eq.rate 2‘X) Ml/d (110/1.163/1) (110/1.163/1) (584/-) (110/1.163/1)

See Next Page For Notes and Sources GENERAL NOTES: STW Severn Trent Water Ltd SSW South Staffordshire Water Ltd

The numbers in italics refer to the section of the licence or variation which gives the limitation - eg 163/2a refers to licence 18/54/2/163 variation special condition 2a. N/A means that no limitation is applicable for this period. Maxima given without a source reference are implied maxima * ie they follow from the restrictions documented.

Hourly abstraction volume limits have been expressed in flow units of Ml/d, but the daily limits may prevent abstraction at the max hourly rates for 24 hours. Similarly, the seasonal and annual abstraction volumes have also been expressed as Ml/d equivalents by dividing the total volume by (he number of days in the period, therefore the daily limits may allow abstraction at higher rates as long as periods of lower abstraction follow.

SPECIFIC NOTES MARKED ON TABLE : ft DAILY MAX: Individual licence daily maxima for 110 and 163 are 400,000 m3 (110/-, 163/-), but this is also thecombined daily limit for these two (and also for the three) licences (110/1,163/1,584/3). A special condition limits the abstraction on 163 to 320,000. m3 per day when Bewdley flow is above 1100 Ml/d (162/2b). The default operating split (Hampton Loade 163:Trimpley 110) of the 400,000 m3 combined 110 & 163 total given in the licence variation (and operational whenever no alternative overriding agreement is in force) is 220,000:180,000 (110/2a,163/2a). For the summers of 93 & 94 a temporary agreement split the maxima 240,000:160,000. In 1995, the licence variation default special conditions applied. Splits i:. between 110 & 163 may be varied proportionally in the future by agreement.

* ANNUAL MAX : Individual licence annual maxima for 110 & 163 are 88,430,000 m3 (110/-, 163/-), but this is also the combined annual limit for these two licences (110/1,163/1). The default operating split (Hampton Loade 163:Trimpley 110) of the 88,430,000 m3 combined total given in the licence variation (and operational whenever no alternative overriding agreement is in force) is 66,430,000:22,000,000 (110/1,163/1). In 1995, the licence variation default special conditions applied. Splits between 110 & 163 may be varied proportionally in the future by agreement. Note that the annual limit applies to a calendar year on licences 110 & 163, but to any twelve consecutive months on 584.

\ $. Abstraction must be taken in a uniform & continuous manner with only 1 change of rate per ' day (584/10).

£ NRA/Agency reserves the right to request that abstraction is taken in a uniform & continuous manner when Bewdley flow is 1100 Ml/d or less, as long as notification (in writing) of the stan and end of uniform rate periods is given (584/11).

The formula for calculating the maximum hourly abstraction on licence 585 when Bewdley flow is in the range 1100 to 2000 Ml/d is -Max Hourly Volume (m3) = 4.185 X Bewdley flow (Ml/d) + 8729.

DATA SOURCES: 18/54/2/163 Variation August 1981 S. Staffs and Severn Trent at Hampton Loade 18/54/2/110 Variation August 1981 Severn Trent at Trimpley 18/54/2/584 Licence January 1995 : S.Staffs at Hampton Loade Figure A2.3 : 1995 MAXIMUM RATES OF ABSTRACTIONS'FROM THE RIVER SEVERN FOR PUBLIC WATER SUPPLY

STW Severn Trent Water Ltd NOTE : Rates as applicable during 1995 v SSW South Staffordshire Water Ltd ’ i Notes (U These daily rates apply only when Clywedog discharge is = or > 500 Ml/d and maximum discharge is being made from Shropshire Groundwater. ^ 18/54/2/584 new licence 01/95 with clauses relating to licences 18/54/2/163 and 18/54/2/110, including combined volumes. (3) Maximum daily abstraction at Hampton Loade must not exceed 320.0 Ml/d if Bewdley flow is greater than 1,100 Ml/d. Hourly limitations also apply. (4) ,For period to 31/12/95 only.

The Environment Agency manage the River Severn Regulation Scheme. The Operations Team in the Water Resources Section at the Midlands Region headquarters determine the release requirements on a daily basis.

The regulation releases from the three resource components can take up to four days to reach the regulation control point at Bewdley. Thus, releases are made based on estimates of the support that will be needed at Bewdley in a few days time. This requires estimates of future abstraction demands and future natural flows, expressed as a recession from the current natural flow at Bewdley. A spreadsheet is used to assist with the modelling, and is an invaluable tool for quickly experimenting with various release / abstraction / recession scenarios. The data sources and the technique used to determine the release requirements are summarised below.

River Flow and Resource Release Data Sensitive ultra-sonic flow measurement equipment at Bewdley and Buildwas provide accurate, reliable, and up-to-the-minute flows on the River Severn, readily available using the standard datalogging and telemetry system. Telemetered level sensors downstream of Llyn Clywedog and Lake Vymwy allow accurate measurement of the reservoir releases. The borehole pumping rates vary little over time, and a reasonable estimate of the net groundwater input is obtained in real time by summing the known individual borehole pumping rates and factoring by 0.85 to allow for pipeline losses and reduced river baseflows.

Abstraction Data The actual and predicted daily abstractions from the 4 principal abstractors upstream of Bewdley are sent weekly to the Operations Team on postcards, and daily phonecalls are made to Hampton Loade and Trimpley to update these values. The recent installation of telemetry at Hampton Loade gives real time access to pumping rates over the Public Service Telephone Network.

Past and Future Recession Estimation Accurate measurements of recent abstractions and recent flows are essential to the real time calculations of the past recession. This is used as a guide to estimating the future recession, which is used in combination with the future abstraction predictions to determine the future release requirements.

The observed flow at Bewdley is naturalised by adding major abstractions and subtracting the known releases, allowing for the release travel time. The calculated natural flow recession over the last few days is then us<£d as a guide to estimating the future recession. Yesterday’s observed recession at Buildwas, upstream of the two major public water supply abstractions, can be used as a guide to the expected recession at Bewdley today, given that the two sites are 40 Km apart.

Rainfall Effect on Flow Recession When rainfall is expected, the modelled recession is adjusted to reflect the estimated additional runoff. Weather forecasts for the next five days are received every afternoon, indicating the rainfall totals expected over the next 48 hours and the forecaster’s confidence in those predictions. Additionally, real time rainfall radar tracks the movement and development of rainstorms over the catchment. After the rain has fallen, the regional flow forecasting system can quickly gather and display rainfall and flow data from many locations in the catchment, and can model the effect of rainfall on the downstream flows. This is very helpful when estimating both the liming and magnitude of the natural flow rises and falls.

1995 Drought Report Page A ll Environment Agency - Midlands Region 1995 Drought Report Page A! 2 Environment Agency - Midlands Region APPENDIX 3 : RIVER SEVERN REGULATION 1995 - DIARY OF SIGNIFICANT EVENTS

Previous Summer - April 94 to October 94

Rainfall in the catchment upstream of Bewdley during the summer of 1994 was significantly below average with June to August rainfall only 60% Long Term Average (LTA). However, an exceptionally wet September (with rainfall 160% LTA) ended the Severn Regulation season after just 68 days. A rapid reduction in soil moisture deficits followed, with a return to field capacity upstream of Bewdley by early November, enabling an early start to the groundwater recharge season. • Previous Winter - November 1994 to March 1995

Heavy rainfall during December, January and February of 170% LTA ensured continued aquifer recharge. Groundwater levels in the key observation boreholes upstream of Bewdley showed a marked recovery over the winter period, but the effects of the prolonged drought of 1989/90/91 were still evident, and groundwater levels were around or just below their seasonal averages by March. Groundwater levels were similar to those before the 1989 drought but generally higher than before the 1975/76 drought.

t Winter rainfall caused overtopping at both Clywedog and Vymwy reservoirs, wiping out all the Vymwy Water Bank balance remaining from 1994. Deliberate flood drawdown and hydro-power releases brought storages down to 97% and 98% respectively by 1st April. ■» Spring - April 1995 to May 1995

April was dry, with rainfall upstream of Bewdley only 38% LTA, leading to a rapid decline in river flows. With Bewdley flows below 1400 Ml/d, the Severn Regulation Alert was issued on 5th May. Heavy rain mid-month followed, however, slowing down the rate of flow recession, and regulation was.not required as imminently as had been anticipated.

June 1995

With Bewdley flows below 1000 Ml/d and upstream abstractions of around 200 Ml/d, regulation began on 17th June with Llyn Clywedog releases increasing to 165 Ml/d. Clywedog was’95.7% full at this time, and Vymwy Bank balance stood at 2295 Ml. Given an average summer, the aviailable resources from Clywedog and Vymwy would be sufficient to 'maintain Severn Regulation support throughout the season, so the issue of the Shropshire Groundwater Scheme Alert was not considered necessary at this time.

Release requirements quickly rose with natural Bewdley flow recessions of 25 Ml/d per day. By 25th,. Clywedog was releasing 450 Ml/d, but was gradually reduced to 350 Ml/d by 28th.

From 29th, Trimpley abstractions rose from 40 Ml/d towards 100 Ml/d. 18 Ml/d (raw) was transferred to Frankley to support supplies from the Elan Valley Reservoirs, while newly increased treatment capacity at Trimpley works (from around 20 to 60 Ml/d) enabled additional abstractions to be treated to provide supplies to North Worcester. This new treatment capacity and strategic supply link was intended to panially replace the Barboume abstraction and treatment works downstream, but the closure was delayed due to the high demands. Meanwhile, Hampton Loade abstractions exceeded 200 Ml/d and the hot, dry weather produced high spray irrigation demands, although half (48) of the licences upstream of Bewdley tied to measured flow sites had been restricted between 14th and 28th June. *

1995 Drought Report Page All Environment Agency - Midlands Region

I " Vymwy releases were increased from normal compensation of 45 Ml/d to a sustainable 70 Ml/d on 29th, and the Shropshire Groundwater Alert was issued for Phase II (South Perry and Montford) of the scheme, with an expected start date after 7th July. With Clywedog storage already falling at a rate of over 5% per week, releases had to be increased to 420 Ml/d on 30th, and V y m w y releases rose to I 10 Ml/d.

J u ly 1995

Cooler, damper weather early in July slackened the rate of recession and reduced irrigation demands, allowing Clywedog releases- to be cut and Vymwy releases to return to. normal compensation. Although 80% of the restrictable spray irrigation licences above Bewdley had been prevented from abstracting by 10th, high public water supply abstractions continued, and releases rose again between 7th and 10th.. On the 10th, the instruction was issued to commence pumping from Phase II of the Shfopshire Groundwater Scheme (SG WS) the following day, with an estimated net output of 45 Ml/d. The Alert for Phase I was also issued, with an expected start date of 24th July or later.

Thunderstorms on 10 th /11th were much heavier than expected, with over 60mm falling in the Welsh mountains and average rainfall upstream of Bewdley around 20mm. Clywedog releases were cut to 160 Ml/d and Vymwy returned to compensation on l 1th. With further rain forecast and Clywedog storage at a healthy 79% full, the decision was made to turn off the expensive borehole support on 13th.

High turbidity after the storm and a diesel spillage pollution incident prevented Hampton Loade from abstracting for two days, resulting in a drawdown at Chelmarsh Reservoir of 450 Ml, so the high storm runoff could not be utilised. The second expected burst of significant rain did not materialise, however, and Clywedog releases had to be increased on 14th to 400 Ml/d to support the high predicted Hampton Loade abstractions,of around 260 Ml/d to top up the bankside storage.

Rainfall upstream of Bewdley averaging around 12mm enabled Clywedog to be reduced to 200 Ml/d on 18th, but it soon rose to 300 Ml/d. By 28th further support was required so Vymwy was increased to 80 Ml/d and the full output from Phase II of the SGWS recommenced.

August 1995

Hot weather and high supply demands continued into August. Hampton Loade demands were now 220 Ml/d and Trimpley was transferring 20 Ml/d to Frankley. The natural flow recession was higher than anticipated, with natural Bewdley flows falling below 600 Ml/d. Releases from Vymwy were raised to 1 10 Ml/d on 4th, and Clywedog releases increased to 400 Ml/d on 6th but these changes were not early enough. With an unexpectedly large Trimpley abstraction of 131 Ml/d (compared to their prediction of 85 Ml/d) on 5th, Hampton Loade’s abstraction was restricted for the first time in the 1995 Regulation Season on 6th to protect the maintained flow. The abstraction was limited to 100 •Ml/d rather than the forecast requirement of 212 Ml/d.

Pumping from Phase I of the SGWS (in addition to Phase II) commenced on 7th with a net output estimated at 40 Ml/d. Hampton Loade’s abstraction was again restricted to zero on 7th and 180 Ml on tlie 8th, producing a drawdown of 340 Ml at Chelmarsh Reservoir. Clywedog releases were increased to assist the Chelmarsh top-up, although actual abstractions were significantly .less than Hampton Loade had predicted. With Clywedog storage now falling at a rapid rate of 5.5% per week, the crossing of the Seek Drought Order control line was expected early in September.

1995 Drought Report Page A N Environment Agency - Midlands Region Severn Trent Water were warned on iOtli August that 54 days of regulation had expired, to allow them to review their Trimpley abstraction scenario in view of the 100 Regulation day licence limitations. With their recent high abstractions including support to the Elan Valley aqueduct supplies, their remaining licensed quantity allowed an average abstraction of just 47 Ml/d for the remaining 46 days.

Hampton Loade abstractions were again restricted on 12th to 150 Ml rather than their required 250 Ml. With natural flows at Bewdley falling towards 550 Ml/d, Clywedog releases were increased to 475 Ml/d. The Maximum Regulation Alert was issued on 14th, signifying the expected increase in Clywedog releases to 500 Ml/d. Vymwy releases were cut to 70 Ml/d on 18th to conserve the banked resources (now 2100 Ml) for a proposed fish habitat sampling exercise, requiring minimal output from Clywedog hence large releases from Vymwy instead. Clywedog releases were increased to 495 Ml/d. on 20th and Vymwy releases had to be increased to 100 Ml/d on 23rd to ensure the maintained flow could be met over the coming bank holiday weekend. These additional short term high Vymwy releases prevented the state of Maximum Regulation being reached during 1995, and the 495 Ml/d Clywedog releases were the seasonal maximum* occurring when natural flows at Bewdley reached a minimum of 540 Ml/d.

By 23rd, restriction letters had been issued to all the restrictable spray irrigators upstream of Bewdley, accounting, for about a third of the total spray irrigation demand.

Both reservoir releases were cut on 25th after the.Trimpley abstraction had reduced from 70 to 37^. Ml/d to keep within the 100 day limitations. North West Water Ltd’s direct abstraction from Vymwy Reservoir reduced from 235 Ml/d to 200 Ml/d towards the end of August when the Vymwy storage : fell below 50% full. This helped to reduce the rapid rate of fallen storage, which had been running at 3.8% per week since the start of June.

September 1995

The releases from Vymwy were increased on 2nd to the maximum output possible to prevent saline water reaching the Gloucester and Sharpness canal abstraction point during the high spring tide period. Clywedog releases were maintained at a high rate for normal regulation requirements. The volume of these saline intrusion prevention releases above normal regulation requirements amounted to 498 Ml, using 20% of the remaining Vymwy Bank resources. The maximum output achieved from Lake Vymwy was only 270 Ml/d since one of the two release valves was unavailable due to public water supply quality considerations. North West Water Ltd were carrying out maintenance work at their usual reservoir abstraction point, forcing abstraction from alternative pipework adjacent to the second release valve. The quality of the public water supply transfer would havejbeen significantly impaired by disturbances caused by the operation of the second release valve.

Light rain enabled the releases at Clywedog to be cut to 200 Ml/d on 5th, and Vymwy was cut back to compensation on 6th. Both Phases of SGWS were turned off on 7th. Clywedog was further cut to 100 Ml/d on 8th after confirmation that the resulting low flows in the upper reaches o f the Severn would not cause distress to fish.

Regulation temporarily ceased on the ilth after 86 consecutive days following around I 5mm of rainfall over the catchment upstream of Bewdley, peaking at 30mm over parts of' Shropshire. Clywedog releases were reduced to the minimum compensation of 18.2 Ml/d to conserve storage, now at 43% full, just 5.1% above the Seek Drought Order control curve. Lake Vymwy storage was similar at 42% full with 1898 Ml remaining in the bank.

1995 Drought Report Page AI5 Environment Agency - Midlands Region A fish habitat survey requiring low levels downstream of Clywedog was planned for 13th, taking advantage of the low Clywedog releases during the break in regulation. The effect of the rains was short-lived, however, and support was again required on 13th when natural Bewdley flows fell below 1000 Ml/d. Both Phases of the SGWS were switched on, and the fish habitat survey confined further support to the Vymwy source. When the exercise was completed, support was switched from Vymwy to Clywedog, but uncertainties in the travel times of releases from the two reservoirs resulted in surplus releases during the switch over. Bewdley natural flows now fell to 800 Ml/d, much higher than the late-August minimum, and Clywedog releases up to 200 Ml/d were adequate.

Heavy rain, averaging about 10mm upstream of Bewdley, enabled Clywedog and Vymwy releasesjo be cut to compensation flows on 24th and 26th respectively. The rainfall allowed Clywedog storage, to begin to rise from its minimum of 40.5% on 24th, 5.4% above the Seek Drought Order control curve. Vymwy reservoir now stood at 36.2% with 1285 Ml in the bank. All the SGWS boreholes were turned off on 26th, anticipating that they would not be required for at least a week. This marked the end of the second period of Severn regulation, ending on the-100th day.

✓ The break in Regulation allowed Trimpley abstractions to temporarily rise to around 90 Ml/d, and the additional abstraction was used as a partial substitute for the Elan transfer to conserve storage in the Elan Valley Reservoirs. Raw water from Trimpley was pumped into the Elan Valley Aqueduct for treatment at Frankley works.

October 1995

With Clywedog’s storage 50 close to the Seek Drought order line, its resources were to be used • sparingly. However, recessions were sharper than expected and regulation support had to recommence on the 1st and the Clywedog release was raised to 200 Ml/d, this being the only support source controllable during a weekend. On 2nd, both groundwater Phases were turned on and support was transferred to Vymwy at a rate of 150 Ml/d. This was the highest Vymwy regulation release of the season. Clywedog releases were cut to minimum compensation to prevent further drawdown. During this regulation period, Trimpley abstractions returned to 60 Ml/d, the maximum allowable rate for Regulation Days beyond Day 100.

Heavy rains over the period 3rd to 7th, averaging about 20mm upstream of Bewdley, temporarily put ' an end to regulation releases on the 5th. Vymwy releases were returned to compensation, and both Phases of the SGWS were turned off, ending the third period of Severn regulation after 105 days in total. Inspection and urgent maintenance work on the scour valves and plugs at Llyn Clywedog involved divers working at their maximum safe depth to reach the .bottom of the dam, so the high inflows had to be wasted in order, to prevent the reservoir level rising. Releases up to 300 Ml/d were made from the 7th to 19th until the work was finished. The total volume of additional releases over normal regulation requirements for this period was 1238 Ml, which would have produced a welcome recovery in storage at Clywedog of approximately 2.5%.

Further regulation support was required on 17th, and both SGWS Phases were turned on, when Clywedog’s constant-level releases were 70 Ml/d. When the maintenance work at Clywedog was finished on 19th, releases were cut to minimum compensation to conserve storage. From 20th to the 24th, Vymwy releases were increased to their maximum for the second time this season to assist with holding back the saline water during the high spring tide period. The volume of releases above regulation requirements amounted to 410 Ml, some 21% of the remaining bank volume.

Further rainfall averaging 15mm upstream of Bewdley enabled both Phases of the SGWS to be turned off on the 25th, ending the fourth period of Severn regulation on Regulation Day 114. Abstractions at Trimpley immediately rose to 1 10 Ml/d.

1995 Drought Report Page A 16 Environment Agency - Midlands Region. November 1995

By 2nd, limited regulation support was again required, so-Phase I boreholes were turned on and Vymwy releases were increased to 80 Ml/d so that Clywedog resources could be conserved. The declaration of a Regulation Day forced Trimpley to almost halve their abstraction to 60 Ml/d. Phase II borehole support commenced on 6th, but recessions were faster than expected and the additional support was too late. Hampton Loade abstractions had to be restricted for three days (6th to 8th) to protect the Bewdley 5-day mean flow, resulting in a Chelmarsh drawdown of 145 Ml, whilst , Clywedog and Vymwy releases were increased to 100 and 110 Ml/d respectively. By 9th following light rain, natural flows had risen above 1000 Ml/d again, and the fifth period of regulation support ended on 1 Ith, the 124th Regulation Day. The regulation season ended with Clywedog at 44.1% fulj. Only 697 MI remained in the Vymwy bank , and Vymwy Reservoir reached its 1995 minimum storage of 29.7%.

Clywedog returned to the minimum generation flow of.around 35 Ml/d rather than the minimum compensation of 18.2 Ml/d. This enabled the generation of hydro-electric power for on-site use (rather than purchasing power from the grid), and was allowed because winter rainfall modelling scenarios suggested only a slim chance of the reservoir not refilling by the next spring.

With natural Bewdley flows around 3000 Ml/d, and resources still available from the Vymwy bank, the Shropshire Groundwater Alert was called off on 17th. With a change in the weather to a more typical autumnal procession of frontal systems, the end of the Severn Regulation Alert was declared on 23rd, after having been in force for 203 days. •: :

Following Winter - December 1995 to March 1996

Cooler weather, lower evaporation and lower demands ensured river flows needed no further regulation support, however, rainfall in the Welsh mountains was only 65% LTA during December and 45% LTA in January 1996. This severely hampered winter reservoir refill, producing end of year storages of 58.2% at Clywedog and 43.0% at Vymwy. By 1st April 1996 Clywedog storage was 87.2% full and V y m w y 73.1% full compared to average storages of 95% .and 98% respectively.

On 26th January 1996, Clywedog releases were cut from around 45 Ml/d to the minimum allowed compensation of 18.2 Ml/d to improve refill prospects. This prevents the generation of electricity to run the dam operations, necessitating the purchase of power from the grid. Severn Trent Water Pic run the operations on behalf of the Environment Agency, and these running costs will be recharged to the Environment Agency under the management agreement.

North West Water Ltd applied for a Drought Order at Lake Vymwy to assist winter refill by reducing the downstream compensation releases. The Drought.Order ran from 16th March until 15th June 1996. Full details are given in Appendix 1. The Drought Order also reduces the potential gains to the water bank. However, the bank stood at 3807 Ml on 1st April, some-2350 Ml higher than normal since carry over at the end of the summer season is usually used up with flood drawdown releases or overflows the following winter.

The high soil moisture deficits accumulated over the drought period did not fall to less than 10mm upstream of Bewdley until early February, reaching a minimum of )mm at the end o f March before starting to increase again. The failure of the soils to reach field capacity over Shropshire and mid- Severn will have reduced the winter groundwater recharge and will be evident in reduced baseflows to rivers in 1996.

1995 Drought Report Page A1J Environment Agency - Midlands Region 1995 Drought Report Page A 18 Environment Agency - Midlands Region APPENDIX 4 : DISCUSSION OF 1995 RIVER SEVERN REGULATION EFFICIENCY

A4.1 Introduction

The daily distribution of total and additional releases compared to the naturalised and maintained flow at Bewdley is shown on Figure A4.1, where the term ’additional releases’ represents all releases above those required to support the 4 main abstractors upstream of Bewdley and to maintain to Bewdley 5-day flow of 850 Ml/d. The monthly distribution of the additional releases is shown on Figure A4.2.

Some of these additional releases were made deliberately for operational or environmental reasons, but the non-deli berate additional releases due to forecasting errors or safety margins can be termed ’excess’ releases. The ideal aim when operating the Severn Regulation System is to have zero excess releases, thereby conserving the available support resources. Realistically, this can never be achieved operationally as it would require perfect knowledge of past and future abstractions, natural flow recessions and rises (after rain), and release travel times. Excess releases will inevitably occur when rainfall is heavier than expected, or when the natural flow recession is not as sharp as expected, or when abstractors take less than predicted (for example, due to a pollution incident in the river, or reduced demands).

The term excess releases tends to imply that these non-deliberate surplus releases are wasted and have no value. On the contrary, this additional How provides more dilution of sewage effluent and benefits water quality. In the upper reaches in particular, additional releases significantly enhance river levels and flows, providing improved, more stable conditions for aquatic life.

During the 1995 Regulation Season (17th June to 11th November), 5% of the total excess releases were attributable to abstractors taking less than they predicted. Rain falling after ' releases had been made accounted for a further 12%. The remaining 9% of total releases resulted from forecasting margins and errors. The total excess releases of 26% in 1995 compares with 19% in 1989 and 16% in 1976. Some of the factors influencing the 1995 excess allocation are discussed below. The general methods and tools used to determine the required releases are described in Appendix 2.

A4.2 Increasing Risk As Drought Developed

At the start of the 1995 Regulation Season when resources appeared to be ample, the Operations Team adopted a Mow risk of failure’ policy (where ’failure’ is a breaching of the Bewdley 5-day 850 Ml/d flow requirement). The quantities released allowed for large error margins in the predictions of future abstractions and natural flow rises or recessions, giving a low risk of failure to meet the abstraction demands and the Bewdley maintained flow. This is reflected in the large forecasting error volumes for June and early July shown on Figure A4.-2

As available resources were depleted and the drought situation became more critical, the risk of failure increased as the error margins allowed for were reduced. The team exploited the 5 day prescribed flow requirement. Releases were made to attempt to meet the mean daily flows of 850 Ml/d at Bewdley every day, but, if forecasts were in error and the flow was not met, it was compensated for by higher flows on subsequent days.

1995 Drqught Report Page A 19 Environment Agency - Midlands Region A4.3 Abstractions

A4.3.1 Need For Abstraction Data

The accuracy and timely availability of both recent and forecast abstraction quantities has a strong effect on the excess releases. Obviously, it is crucial to know the future abstraction demands to ensure that releases made today from the support sources will meet the demands of the abstractors when they have travelled down river and arrived at the abstraction point up to four days later. Past abstraction data is also necessary, since recent abstractions are used to calculate the natural flow recession and thereby predict the future recession. If yesterday’s true abstraction was more than the estimated abstraction, an over-estimate of yesterday’s rate of natural flow recession will result. This may lead to an over-estimate of the future recession and consequent over-release from the support sources.

A4.3.2 Source of Abstraction Data

Actual and predicted abstraction data for the four major abstractors upstream of Bewdley were sent weekly on postcards throughout 1995. By the time the predictions were received, however, it was often half way through the week to which the predictions applied. Consequently, daily phone calls were made to the two principal abstractors at Hampton Loade and Trimpley to get accurate up to date measurements of yesterday’s abstraction and to update the forecasts of today’s and future abstractions.

, Telemetered data loggers installed at Hampton Loade gave both daily and instantaneous pumping rates, as well as the level at Chelmarsh bankside storage reservoir. Similar equipment was not available at Trimpley, but is planned for late in the summer of 1996.

It often proved difficult to contact staff at Trimpley for daily updates of past and future abstractions, and data loggers would have been extremely useful. The forecasts given by the staff often bore little relationship to the actual abstraction, thwarting release efficiency. For example, the abstraction on 5th August was 131 Ml compared to a prediction of 85 Ml. These t problems were more significant in 1995 than in previous years because Trimpley’s abstractions were much greater. Complaints about poor contact and forecasts were passed on during meetings with Severn Trent Water Ltd, and the company agreed to collate actual and predicted Severn abstractions at their Barboume works and fax them to the Operations Team mid-week from early October. This helped to improve the'quality of Trimpley’s longer term abstraction forecasts, but daily phone calls were still required to update the actual abstractions.

A4.3.3 Causes and Effects of Changes to Predictions

The post card estimates tended to be on the high side, and actual abstractions were generally less than predicted. Since resources are released to meet the predicted future abstraction demands, over-prediction of abstractions will result in over-release of resources. Downward changes to the original (card) future abstraction plan notified during the daily telephone calls often came too late; the releases to serve the original predictions had already been made.

Reductions in abstraction may arise due to unforseen circumstances such as a pollution incident or pump failure. When summer thunderstorms occur after a prolonged dry period, the turbidity of the storm runoff can prevent abstraction on quality rather than quantity grounds, such that the storm water is itself a pollution incident. Thus, the short-lived surplus natural river flows cannot be utilised, and higher than normal abstractions (requiring higher releases) to top up the drawn down bankside storage follow when river flows have fallen.

1995 Drought Report Page A 20 Environment Agency - Midlands Region A4.3.4 Use of Bankside Storage

The South Staffordshire Water Ltd (SSW) abstraction at Hampton Loade averaged 184 Ml/d during the summer of 1995, and had a huge impact on the Bewdley flow. The water is pumped to Chelmarsh bankside storage reservoir where there is potential to modulate the Bewdley flow by deliberately keeping the reservoir partially drawn down. This,would create free storage capacity to make use of any surplus flows in the river caused by either natural runoff or accidental over-release, and abstractions on subsequent days could then be reduced, conserving release resources.

In 1995, SSW understandably tried to top up the bankside storage every night to provide maximum security of supply in the event of a major pollution incident preventing river abstractions for a few days. Additionally, by drawing on the reservoir storage in the daytime and refilling overnight, they were able to pump from the Sevem at the most economical rates, taking advantage of the cheaper nighttime electricity tariffs.

The National Rivers Authority, under a Section 20 (Water Resources Act 1991) Operating Agreement, reserve the right to request short-term abstraction restrictions to maintain the Bewdley flow. However, the NRA and SSW agreed a financial arrangement at the start of the 1995 designed to compensate for the additional costsentailed in pumping the required volume at a later time under less favourable electricity tariffs. The compensation payable was directly proportional to the volume of the abstraction restriction (compared to the original prediction). This was the first year that a strict compensation formula had been applied; previous; restrictions had been accepted on a goodwill basis, or with a nominal compensation payment. Consequently, the NRA tried to release sufficient support for the forecast abstraction requirements to be met.

A4.3.5 Spray Irrigation

Spray irrigation demands upstream of Bewdley are likely to have exceeded I 00 Ml/d in the hot dry spells early in the summer of 1995, probably averaging 70 Ml/d in June and July. The . abstractions are scattered throughout the catchment -and there is no practical means of collecting live data so it is difficult to quantify the effects on the Bewdley flows. Spray irrigation demands are not explicitly included in the release calculations, so any changes in irrigation abstraction rates will be reflected in the calculated recession. Gradually increasing demands will enhance the natural flow recession spreadsheet calculation, which can result in an over prediction of the future recession and consequent over release of resources.

A4.4 Rainfall * A4.4.1 Past Rainfall

When rain falls, the observed mean daily flow at Bewdley varies widely between days and will be significantly influenced by the chosen day boundary time. Unfortunately, this results in a very ’fuzzy’ estimate of the recent flow recession or rise, since the spreadsheet calculations are based on daily mean values and multiple (whole) day release travel times. Recession forecasting, guided by the recent observed recession, is therefore very difficult.

1995 Drought Report Page A 2 1 Environment Agency - Midlands Region A4.4.2 Future Rainfall

Estimation of the effects of future rainfall on the Bewdley flow recession is also very difficult. The releases from the three components can take up to four days to reach the control point at Bewdley, but the rainfall effect can be felt much earlier, so predictions of flow rises should ideally be made before the rain has fallen.

Real-time weather radar was of little use for forecasting rainfall more than a few hours ahead. The contracted 5-day weather forecasts were helpful in 1995, but it was difllcult to predict the cumulative overall effect (in terms of flow and timing) of all the storms upstream of Bewdley since the summer storms were often localised downpours, forecast with low confidence. Even forecasts of heavy rainfall could not be relied upon, and there was a large risk of failure to meet the maintained flow if releases were reduced too soon. Consequently, the regulation releases were often cut after the rain had fallen, inevitably wasting the releases already made that coincided with the naturally enhanced runoff. The rainfall quantity was measured by the regional raingauge network, and its influence on downstream flows was predicted using the regional flow forecasting model. Release requirements reductions could then be more accurately reassessed, although the performance of the flow forecasting model is limited at low flows since it was designed for flood flow modelling.

The monthly distribution of excess releases apportioned to rainfall after release shown on Figure A4.2 reflects the more frequent storms during, July and September. Total excess' releases were much lower during the exceptionally dry August when rainfall did little tp complicate the recession pattern. y

1995 Drought Report Page A22 Environment Agency - Midlands Region Bewdley Flow Ml/d 2000 1500 1000 500 * Figure : DailyA4.1AnalysisRiver of Severn Regulation Releases 1995 showing Bewdley flow and releases above normal minimum compensation minimum normal above releases and flow Bewdley showing RequiredRegulation J£L Releases uut etme Otbr November October September August

. Additional Releases

Natural Flow 5-Day ResidualFlow 5-Day NaturalFlow ede Bewdley Bewdley High Tide High Releases

Clywedog Maintenance ih Tide High Releases

Additional Release in Ml 00 - 4000 2000 5000 3000 6000 1000 iueA. : otl itiuino 95 ie een euainAdtoa Releases Additional Regulation Severn River 1995 of Distribution Monthly : A4.2 Figure June te eessctgr icue : includes category Releases Other Note - Severn Regulation was operational from 17/06 to 11/11 in 1995, hence the lower June and November totals November and June lower the hence 1995, in 11/11 to 17/06 from operational was Regulation Severn - Note ii) Additional Vyrnwy releases due to Noth West Water maintenance Water West Noth constraints to due operational to due releases releases Vyrnwy ii)Additional additional and testing Groundwater Shropshire i) iv) Additional releases made during change of resource for habitat survey ' - ' survey habitat for resource of fisheries protect to change storm during major made after releases releases Additional iv) Clywedog of cut-back gradual Deliberate iii) July August i .

1995 September I:: :* October paaij □ November Abstractors Rainfall Subsequent Error Margin Error Support Other Error Margin Error Forecasting ih Tide High Maintenance Clywedog Releases

APPENDIX 5 : RIVER DERWENT OPERATIONS 1995 - DIARY OF SIGNIFICANT EVENTS

Previous W inter- November 1994 to March 1995

Heavy rainfall during December, January and February of 156% Long term Average (LTA) ensured rapid winter refill and overtopping of the Derwent Valley and Ogston Reservoirs. Derwent Valley overflows peaked at over 3500 Ml/d on 28th January. Despite deliberate flood drawdown releases, the Derwent Valley reservoirs were still spilling on 1st April, while Ogston. was a healthy 97.3% full. Carsington Reservoir had refilled naturally to 99% full.

Spring - April 1995 to May 1995

- The Derwent Valley flood drawdown releases continued until towards the end of April when'releases returned to the normal 57 Ml/d compensation.

April was dry, with rainfall over the Derwent catchment only 43%LTA, leading to a reduction in reservoir inflows and a rapid decline in downstream river flows. Derby flows first fell below the 680 Ml/d threshold at the end of April. •

Storage at Ogston Reservoir began to fall rapidly. The Ogston Reservoir water suffered from algal quality problems, so a 45 Ml/d transfer of Carsington water direct to Ogston treatment works took place from 26th April. The transfer provided all the Ogston supply needs, so Ogston Reservoir levels' held steady. By 15th May, the Carsington transfer ceased and the first abstractions of 1995 from tl\e River Derwent at Ambergate to Ogston Reservoir commenced at 15 Ml per day. This is the maximum ’ rate allowed when Derby flows are between 340 and 680 Ml/d, and, since supply from Ogston Reservoir was greater than the inflows, the reservoir storage started to fall again.

Ju n e 1995

June was another dry month, with rainfall over the Derwent catchment only 29% LTA. Derby flows continued to fall and support from Carsington to maintain the 340 Ml/d flow was required by mid June, initially at a rate of 30 Ml/d. If the Derby flows fall below the 340 Ml/d threshold, abstraction allowances are reduced at Little Eaton and prevented at Ambergate, and additional compensation from •the Derwent Valley Reservoirs is required. Pumping from the Derwent to Ogston Reservoir stopped ■ while Carsington releases to support the Derwent were required, and the transfer of Carsington water to Ogston works recommenced at 22 Ml/d to reduce the rate of drawdown at Ogston.

At the same time, releases from the Derwent Valley Reservoirs were increased from 57 to 72 Ml/d. After a week, however, Derwent Valley releases were returned to normal and all support of the Derby 340 Ml/d flow threshold came from Carsington in preference. By the end of the month, transfer rates were increased to 50 Ml/d while the Carsington releases to the Derwent rose to 91 Ml/d.

Output from the Bamford treatment works (Severn Trent Water btd’s supply from the Derwent Valley Reservoirs) was reduced as the reservoir storage fell.

When Derwent flows are low, the effects of sluice gate and turbine operations in the liver are enhanced. On 29th June, the first major Belper Pound incident of the summer occurred when the turbines suddenly stopped running. This generated a short-lived low flow pulse downstream, resulting in a minimum flow at Derby of 163 Ml/d and a mean daily flow of 328 Ml/d. A more detailed description of the Belper Pound set-up and operational effects is given in Appendix 6.

1995 Drought Report Page A25 Environment Agency - Midlands Region July 1995

Storage at the Derwent Valley Reservoirs continued to be depleted, and crossed another control curve during July, restricting the Severn Trent Water Ltd supply to 155 Ml/d.

The Carsington to Ogston works transfer continued all month at a rate of around 50 Ml/d. The Carsington releases to the Derwent also continued, reaching 80 Ml/d by the middle of the month. After rainfall, Severn Trent Water slopped the Carsington release on 18th July, but they had underestimated the rate of recession, and Derby flows fell slightly below 340 Ml/d from 20th to 22nd July. The support release restarted on 20th at a rate of 80 Ml/d and gradually increased to 160 Ml/d by the end of the month.

Further Belper Pound turbine variations produced short lived low flows downstream on the 5th, 10th 1 1th and 25th July. The low flow pulses were often followed by high flow pulses, however, and the mean daily flows at Derby were maintained above the 340 Ml/d flow threshold except on 25th when the mean flow was 5 Ml/d short.

Low levels rather than low flows were a problem on 18th July. Courtaulds Ltd abstract around 220 Ml/d from the Derwent for cooling purposes and return about 200 Ml/d further downstream. Both their abstractionand return points are located on a meander of the Derwent, with Spondon (Derby) sewage effluent outflow located in between. The meander neck has been cut through to allow flood flows to take a more direct route, controlled by Spondon Sluices. The sluices had previously opened for high’ runoff following a storm; but had failed to close properly when flows receded. Flow continued to bypass the meander, causing low levels around the Courtau Ids site, and potential quality problems due to insufficient dilution of the sewage effluent in the meander.locality. The problem was solved by closing the back-up set of sluices (behind the main set) at Spondon.

August 1995

Hot weather and high supply demands continued into August. August rainfall was exceptionally low at only 12% LTA over the Derwent catchment, with three month totals only 29% LTA. Derwent Valley reservoir inflows fell to below 40 Ml/d. Natural flows in the Derwent continued to recede, with STW actively managing releases and abstractions in order to maintain the residual flow of 340 Ml/d at Derby, although on 25th flows fell slightly short of the target.

The continuing Carsington support to the Derwent increased to a peak of 186 Ml/d on 8th August, and was always greater than 130 Ml/d through to the end of the month. The Carsington to Ogston transfer was reduced from 50 Ml/d to 30 Ml/d at the time of the peak releases to the Derwent, but rose again when the Derwent releases reduced. The reservoir transfer was stopped on 24th to conserve Carsington storage for Derwent support later in the summer. The percentage storage at Carsington Reservoir was now lower than at Ogston Reservoir. ' ' '

J With the continuing high demands, Severn Trent Water Ltd took advantage of the additional natural and effluent inputs between Little Eaton and Draycott. From 3rd, abstractions to Church Wilne were split between the two abstraction points for the first time since March. Abstraction rates at Little Eaton continued at previous rates of 128 Ml/d while Draycott abstractions began at 35 Ml/d.

By the end of the month, storages had fallen to 44.0%, 66.7% and 63.2% at the Derwent Valley,. Ogston and Carsington reservoirs respectively. The Derwent Valley storage had been falling at 3.4% per week from mid June to mid August, while Carsington fell at a rate of 1.5% per week over the same period. The Carsington transfers direct to the treatment works had enabled Ogston Reservoir storage to hold almost steady.

1995 Drought Report Page A26 Environment Agency - Midlands Region Severn Trent Water Ltd (STW) imposed a regionwide hosepipe ban on 22nd August, which resulted in significant reductions in demand, although this also coincided with a period of cooler, damper weather. With reduced demands, STW supplies from the Derwent Valley Reservoirs were cut to 120 Ml/d, considerably below the control curves maximum supply recommendation, to slow down the rate of storage depletion. Additionally, the supply to Yorkshire Water Ltd was cut to below 40 Ml/d at the end of the month.

September 1995 _

Rainfall in September brought some relief to the serious drought situation, with rainfall over the Derwent catchment 113% LTA. This was the first month in the last six to receive above average rainfall. Reservoir inflows saw a welcome increase, but, with the cessation of the Carsington to Ogston transfer at the end of August, Ogston reservoir storage saw a rapid decline in.September of 4.8% per week, despite the wetter weather.

Following the wet periods, Carsington support to the Derwent was not required on several days between 1st and 11th. Carsingion releases to the Derwent recommenced on 14th at 112 Ml/d and continued through the rest of the month with one short break following rainfall.

Norweb activities at Belper caused flow fluctuations on 4th and 6th, but the Derby mean daily flow was maintained above the 340 Ml/d threshold. Emergency work on the mill.race structure at Belper. was taking place around the 11th, and the pound had been deliberately drawn down slightly. However, a sluice gate stuck open and drained the pound unnecessarily. Severn Trent Water Ltd observed the: resulting flow rise at Derby, unaware at that time of the Belper Pound drainage, and cut off their Carsington support. The manually adjusted pound refill rate was too rapid, and Derby mean daily flows reached a minimum of 262 Ml/d on 12th, with an instantaneous minimum flow of 106 Ml/d, causing STW to restrict their abstractions on 12th and 13th. Fortunately, no water quality or fisheries problems were reported.

October 1995 * . . '

. Drier weather returned in October, with the Derwent catchment receiving 51% LTA rainfall. Carsington support to the Derby flows continued at a rate of 75 Ml/d at the start of the month, rising " to 135. Ml/d by the end, with two short breaks following rainfall.

Ogston reservoir storage fell to its annual minimum of 28.2% on 29th. The Carsington to Ogston treatment works transfer recommenced after a two month break on 30th at a rate of 50 M l/d, allowing the reservoir storage to recover.

November 1995

Early in November, the Derwent Valley Reservoir storage crossed another control line and the Yorkshire Water supply was cut from 40 to 35 Ml/d. Minimum output from the Bamford works (STW supply) was maintained to conserve storage, and river abstractions were able to met the local demand shortfall with flexible use of the supply grid.

With a change in the weather to a more typical autumnal procession of frontal systems, natural river flows rose. Carsington support to the Derwent ceased on 9th but transfers to Ogston reservoir still continued at 50 Ml/d.

1995 Drought Report Page A27 Environment Agency - Midlands Region Now that Derwent releases were no longer required, pumped refill to Ogston from Ambergate commenced on 27th November after a break since the Spring. The flow at Derby was still below the 680 Ml/d threshold, so pumped refill was restricted to 15 Ml per day. Since it is impossible to simultaneously pump from the Derwent into Ogston Reservoir and transfer water from Carsington to Ogston works, the two activities took place for approximately 8 and 16 hours a day respectively at instantaneous rates of around 45 Ml/d. The reservoir storage began to show a slight recovery.

By the middle of the month, most of the Church Wilne abstraction was taken from the downstream Draycott intake at around 100 Ml/d, although smaller, intermittent abstractions still continued at Little Eaton.

Although the reservoir resources had been stretched through the 1995 summer drought, they were just sufficient to maintain supplies (with the hosepipe ban in force), but had ended the season severely drawn down. Severn Trent Water Ltd calculated that average runoff from December to April would just refill the Derwent Valley Reservoirs, and three months of uninterrupted pumping was required to refill Carsington and Ogston. A dry winter would restrict reservoir recovery, so preparations began for Drought Order applications to safeguard supplies in 1996.

Belper Pound activities were frequent during November. On the 1st, a rope on the sluice gates broke, causing the pound to empty. Severn Trent Water Ltd were understandably annoyed that their 130 Ml/d Carsington releases were wasted on refilling the pound. A tree trunk had become stuck in one of the sluices, so on 3rd it was opened fully to flush out the tree, again causing the pound to empty. The' resulting low flows downstream during the pound refill period could have caused serious quality problems if Courtaulds had taken their usual abstraction upstream of Spondon sewage works. Fortunately, Courtaulds kindly agreed to recirculate warm water and draw down their own lagoon for their cooling purposes until flows recovered. The mean daily flows at Derby were maintained above 340 Ml/d, but instantaneous flows fell below 100 Ml/d.

On 20th, Belper Pound was deliberately drawn down to allow the installation of electronics on the flood sluice gates, to enable automatic operation in high flow conditions. Since river flows were still relatively low, refill of.the pound was held off and downstream releases were controlled by manual sluice gate operations to keep the drawn down pound level stable. The NRA gave permission to commence refill on 28th at a very slow rate, spread over a few days. The sluice gates were manually adjusted with frequent monitoring by the NRA, and the mean daily flow at Derby was just maintained at 340 Ml/d with Severn Trent Water Ltd reducing their abstraction appropriately.

December 1995

Winter reservoir refill was hampered by low rainfall of only 82% LTA over the Derwent catchment during December. The Derwent Valley reservoir storage fell below the last control curve, and supply to Yorkshire Water was reduced to 27 Ml/d for two weeks around 22nd when the reservoirs reached a minimum storage of 20.2%.

End of year storages were only 23.5%, 37.1% and 38.6% at the Derwent Valley, Ogston and Carsington Reservoirs respectively. This was the minimum annual storage at Carsington.

Severn Trent Water Ltd took advantage of temporary high flows following rainfall, when Derby flows rose above the 680 Ml/d abstraction threshold for a few days towards the end of the month. The Carsington to Ogston works transfer temporarily ceased while pumping from the Derwent to both Ogston and Carsington took placeT Ogston pumped inflows rose to about 75 Ml per day (previously 15 Ml per day) while the Carsington pumped inflows commenced at over 100 Ml/d. These were the only Carsington pumped inflows during 1995.

1995 Drought Report Page A 28 Environment Agency - Midlands Region Following Winter - January 1996 to March 1996

Supply to Yorkshire Water Ltd from the Derwent Valley Reservoirs reduced further to just 25 Ml/d from early February 1996. Severn Trent Water Ltd’s own supplies were cut to below 100 Ml/d' in January and below 80 Ml/d in February to conserve Derwent Valley storage. In order to meet local supply demands, the flow in the Derwent Valley aqueduct was reversed:

The Carsington to Ogston works transfers finally ceased on 5th January 1996. Ogston pumped inflow continued at 15 Ml/d, but higher flows from the 6th allowed high pumped refill rates at both Ogston and Carsington.

Two Drought Orders were in force from 19th January 1996 until 18th April 1996 to assist with reservoir refill. The Derwent Valley Drought Order allowed a reduction in total compensation from 74 to 51 Ml/d. The River Derwent minimum compensation was reduced from 57 to 34 Ml/d while the River Noe minimum compensation was reduced from . 17 to 12 Ml/d. The Ambergate Drought Order reduced the threshold allowing high rates of abstraction from the Derwent at Ambergate to Carsington or Ogston Reservoirs from 680 to 500 Ml/d. Full details of these drought orders is given in Appendix

I .

The Ambergate Drought Order allowed combined Carsington and Ogston pumped inflow rates up to 180 Ml/d higher than they would otherwise have been. However, the mitigation measures required by p the Drought Order were not in place during January, and flows were naturally high during most of February, so the Drought Order concessions were not used, until early March. Most o f the additional abstractions were taken for Carsington rather than Ogston, due to the lower natural inflows. Total. Ambergate spring abstractions peaked at 269 Ml/d when river flows were high.

With the Drought Orders in force, reservoir storages had recovered to 60.7% at Derwent Valley, 70.3% at Ogston and 73.0% at Carsington by 1st April 1996. These figures compare with average storages of 97%, 88% and 92% respectively for the time of year (the Carsington average has been estimated based on idealised operation). January to March rainfall had been only 74% average over the Derwent catchment.

The regionwide hosepipe ban issued on 22nd August 1995 was not lifted until 29th April 1996 in the East Midlands districts.

1995 Drought Report Rage A29 Environment Agency - Midlands Region 1995 Drought Report Page A30 Environment Agency - Midlands Region APPENDIX 6 : RIVER DERWENT AT BELPER POUND

A6.1 Location of Bclper

The impoundment at Belper is situated on the River Derwent between Ambergate and Little Eaton. At Ambergate, Severn Trent Water Ltd abstract for pumped refill of Carsington and Ogston Reservoirs and release resources from Carsington to support downstream abstractions. These releases and abstractions are subject to sudden large changes, and sometimes operate on 8-hour daily cycles. At Little Eaton, Severn Trent Water Ltd abstract for public water supply.

The nearest flow gauging stations on the Derwent are at Whatstandwell, upstream of Ambergate, and Derby, downstream of Little Eaton. Therefore, the effects of Belper Pound activities are difficult to separate from the Ambergate and Little Eaton activities and the natural flow variations, allowing for the travel times between locations. Fortunately, telemetered data logging equipment has been installed to measure the abstractions and releases and the pound level.

A6.2 Flow Routes at Belper Pound

At Belper, the Derwent is impounded by a long horseshoe-shaped weir and sluice gate.. arrangement, effectively turning the river into a lake, known as Belper Pound. A mi If race to the electricity generating turbines run by-Norweb Generating enables a large proportion of tlfe; total Derwent flow to bypass the weir and sluice gates. The combined flow through the two turbines can exceed 1000 Ml/d with a suitable head of water in the pound. Incoming flows can^ therefore4ake three routes through Belper - over the weir, through the turbines or under the sluice gates. The flood sluice gates leak some flow everi under drought conditions, but can be raised to let high flood flows pass through.

A6.3 Automatic Turbine Control

The turbine guide vanes control the generating power and through flow, and are automatically adjusted according to an ultrasonic pound level measuring device. However, the automatic adjustments will only reduce throughflow to the minimum required for generation. There is no automatic control to stop turbine operation when pound inflows are insufficient to generate power, for example, under drought conditions or when there is a high flow through the sluices. Instead, the turbines will continue draw the minimum required flow through the mill race by running at their lowest output, thereby reducing over-weir flows and draining down the pound. Eventually, the low head will cause the electricity generated to drift out of phase with the grid supply and the turbines will cut out, but, by this time, the pound may have been drawn down below crest level. The turbines will automatically restart when the pound level has risen sufficiently.

A6.4 Effects of Turbine Changes on Downstream Flows

If the turbine suddenly stops operating, this component of the downstream flow immediately ceases. The flow over the weir will gradually increase to compensate, eventually reaching a new equilibrium weir level where the upstream inflows equal the over-weir and sluice gate outflows. The time lag between the instantaneous closure of the turbine outflow and the gradual compensatory increase in over-weir flows results in a low flow pulse downstream (the volume of which will'equate to the additional volume impounded by the increased pound level).

1995 Drought Report Page A3! Environment Agency - Midlands Region The resulting changes in the pound level may only be a few centimetres, and might appear insignificant at first glance, particularly when the pound remains full throughout the perturbations. However, the wide weir acts like a reservoir dam, and a small change in level represents a large change in the impounded volume, and causes large changes in the downstream flows. This effect is clearly illustrated on Figure A6.1.

If the pound level has fallen below the weir level (2.000m) when the turbines cut out, the only outflows remaining will be leakage through the sluices, so downstream flows will be extremely low until the pound refills and spill over the weir recommences. When the turbines are suddenly turned on, the opposite applies and a high-flow pulse results downstream.

Since the turbines are automatically controlled by the level upstream of the weir/on-ofF-on changes can occur in rapid succession causing the downstream low and high flow pulse to generate an S-shaped (zig-zag) flow pattern.

A6.5 Other Activities Causing Changes to Downstream Flows

The turbine operations discussed above- are the cause of most of the' downstream flow fluctuations at Bel per. The pound can also be drawn down or emptied for deliberate maintenance purposes, or due to accidental sluice gate openings, or due to sluice gates failing to close properly after opening for storm flows.

When the pound has been drawn down significantly below weir crest level at a time of low natural inflows, it may be necessary to increase the minimum downstream flows by opening the sluice gates further. This will delay the rate of refill of the pound, but may prevent water quality problems. Unfortunately, the required manual sluice gate adjustments are difficult to estimate, and the flow adjustments will not be observed at the nearest flow measurement site at Derby for several hours.

A6.6 Effect of Flow Changes on Downstream Water Quality and Abstractions

The short-lived low flows can cause quality problems, particularly with lack of dilution for Spondon sewage effluent, downstream of Derby gauging station. It may also limit abstractions, particularly at Courtaulds Ltd where gross abstractions are around 220 Ml/d just upstream of the Spondon sewage outfall.

Severn Trent Water Ltd’s Ambergate and Little Eaton abstractions depend on maintaining a mean daily flow of 340 Ml/d at Derby. This flow is supported by the release of valuable Carsington resources, which are available through winter pumping at great expense. Their abstraction plans can be ruined by Norweb’s activities, causing supply difficulties, and their Carsington support can be wasted during pound refill. With short lived turbine variations, the daily mean flow downstream may not always be adversely affected, as the high and low pulses may balance out. Obviously, this depends on the exact timing of the turbine changes in relation to the 09:00 GMT daily flow calculations. When the pound has been significantly drawn down, however, refill is usually gradual over a period of more than 24 hours and the Derby mean daily flow is inevitably reduced.

1995 Drought Report Page A 32 Environment Agency - Midlands Region Instantaneous Flow Rate (Ml/d) Figure A6.1 : Effect of Belper Pound on Derby Flows Derby on Pound Belper of Effect : A6.1 Figure Derby Flow Level Ogston Reservoir Ogston Level Flow (L. Eaton abstraction for Derby was constant at 5CTMI/d throughout the period) the 5CTMI/d throughout at constant was Derby for abstraction Eaton (L. Belper Pound Belper ae ndt rm 2ht 1t ue 1996 June 16th to 12th from data on Based NOTE : Belper.Pound crest level is 2.0 m 2.0 is level crest Belper.Pound : NOTE Abstractionto \ \ L. Eaton for Nottinghamfor Eaton L. ' Abstraction'at

......

Belper Pound Level (m) \

1995 Drought Report Page A34 Environment Agency - Midlands Region APPENDIX 7 : UPPER SEVERN COMPENSATION SYSTEMS

A7.T The Hadley Brook Compensation System

Severn Trent Water Ltd are required (under the licence conditions) to compensate the Hadley Brook catchment for loss of natural baseflow resulting from their groundwater abstractions in the Ombersley area. Informal operational guidelines relate the required compensation releases to the flow at Ward’s Bridgt gauging station on the Hadley Brook. A portion of the abstraction from the borehole at Dunhampton is released to three Hadley Brook tributary streams from outlets on the pipeline from the borehole to the treatment works. The maximum total compensation release of 2.0 Ml/d (according to the operational guidelines) compares with a total borehole output of about 3.5 Ml/d.

The compensation requirements and 1995 operations are detailed below in Figure A 7.1. This was the first year since the operational guidelines have been in force (1991) that the third stage of compensation was required, -

During a storm on 10th July, a lightning strike prevented automatic control of the compensation releases. All pumping ceased temporarily but, as natural river flows fell, the NRA requested that compensation recommence. All the borehole output was therefore used as compensation from 26th July for a few days until the electronics had been repaired.

STAGE Total Ward’s Bridge Control Flow 1995 DATES Compensation (7-day mean and current) (Ml/d) (Ml/d) Stage On Stage Off Stage On Stage O ff

I 0.6 < 20 > 25 09/05/95 . 10/01/96 11 1.5 < 7 >10 28/07/95 11/09/95

III 2.0 < 6 > 7 22/08/95 01/09/95

TOTAL Compensation over 1995/96 = 185 Ml = 60% of annua! max (306 MI)

Figure A7.1 Hadley Brook Compensation Requirements and 1995 Operations

A7.2 The Strine Catchment Compensation System

Severn Trent Water Ltd are required to compensate the Strine catchment for loss of natural baseflow resulting from their abstractions at four boreholes in the Strine Valley. The compensation releases are made from the Edgmond.borehole to the River Strine at rates up to 3.6 Ml/d when the flow at Crudgington gauging station on the River Strine falls below 30 Ml/d. i Compensation releases began on 26th June 1995 and continued until 25th September at an average rate of 3.2 Ml/d.

The Edgmond borehole provides good quality, low nitrate water. Discussions are currently taking place regarding the substitution of Edgmond water with releases from an old abandoned borehole at Newport. The quality of this water too poor for public water supply but may be adequate for compensation releases.

1995 Drought Report Page A35 Environment Agency - Midlands Region t

/

/

/ 995 Drought Report Page A 36 Environment Agency - Midlands Region