NRA-Water Quality Series 23 The Mersey Estuary a R e p o r t o n E nvironmental Q u a l i t y WATER QUALITY SERIES NO 23 NRA National Rivers Authority Guardians of the Water Environment National Rivers Authority Rivers House Waterside Drive Aztec West Almondsbury Bristol BS12 4UD Tel: 01454 624 400 Fax: 01454 624 409 © National Rivers Authority 1995 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise without the prior written permission of the National Rivers Authority. First Edition 1995 ISBN No.O 11 885844 0 Other titles in the water quality series 1. Discharge consent and compliance policy: a blueprint for the future 2. Toxic blue/green algae 3. Bathing water quality in England and Wales 1990 4. The quality of rivers, canals and estuaries in England and Wales 5. Proposals for statutory water quality objectives 6. The influence of agriculture on the quality of natural waters in England and Wales 7. Water pollution incidents in England and Wales 1991 8. Bathing water quality in England and Wales 1991 9. Water pollution incidents in England and Wales 1992 10. Discharges of waste under the EC Titanium Dioxide Directives 11. Bathing water quality in England and Wales 1992 12. The quality of the Humber Estuary 1980-1990 13. Water pollution incidents in England and Wales 1992 14. Abandoned mines and the water environment 15. Contaminated land and the water environment 16. Implementation of EC Shellfish Waters Directive 17. Discharge consents and compliance 18. Bathing water quality in England and Wales 1993 E n v ir o n m e n t A g e n c y 19. The quality of rivers and canals in England and Wales 1990 to 1992 20. Implementation of the EC Freshwater Fish Directive 21. Water pollution incidents NATIONAL LIBRARY & 22. Bathing water quality in England and Wales 1994 INFORMATION SERVICE HEAD OFFICE Rio House. Waterside Drive, Designed and produced by: Aztec West, Almondsbury, Stotts, 14 Frederick Place, Clifton, Bristol. Bristol BS32 4UD Printed and bound by: Harlequin Colourprint, Bristol. ——————————_ Awarded for excellence The Mersey Estuary a Report on Environmental Quality The Information Centre National Rivers Authority Waterside Drive Aztec West Almondsbury Bristol BS12 4UD Due for return 7- 7 - 1 7 - 7 - 1 * .I Rivers Authority nion Centre >fffce o ENVIRONMENT AGENCY LONDON: HMSO Accession N A w Trt =r» ( 0 9 9 5 8 3 CONTENTS Executive Summary vi Chapter 1 An introduction to the Mersey Estuary 1 1.1 Geography 1.2 Hydrography 1.3 Freshwater Inputs 1.3.1 Riverine Inputs 1.3.2 Manchester Ship Canal Flows 1.4 A Historical Perspective of the Mersey Estuary 1.4.1 Early Development and Growth 1.4.2 The Industrial Revolution 1.5 Land Use Patterns around the Estuary 1.5.1 Ownership 1.5.2 Recreation 1.5.3 Conservation Status Chapter 2 The regulatory framework 7 2.1 Introduction 2.1.1 The Rivers Pollution Prevention Act, 1876 2.1.2 Pollution Prevention Acts, 1951-1961 2.1.3 Water Act, 1973 2.1.4 Control of Pollution Act, 1974 2.1.5 North West Water Authority 2.1.6 The Mersey Basin Campaign 2.2 International Legislation 2.2.1 European Community Directives 2.2.1.1 Dangerous Substances 2.2.1.2 Bathing Waters 2.2.2 North Sea Conference Declarations 2.3 The Water Act, 1989 and Water Resources Act, 1991 2.4 The Environmental Protection Act, 1990 2.5 Future Initiatives 2.5.1 Urban Waste Water Treatment Directive 2.5.2 Integrated Pollution Prevention and Control Chapter 3 The processes which influence estuarine water quality 11 3.1 Introduction 3.2 Physical Processes 3.2.1 Tides 3.2.2 The Impact of Tides on Water Quality 3.2.3 Tidal Excursions 3.2.4 Freshwater Run-off 3.2.5 The Flushing Time of the Estuary 3.2.6 The Behaviour of Dissolved Constituents 3.3 Chemical Processes 3.3.1 Types of Chemical Reaction 3.3.2 Oxygen Demanding Reactions 3.3.3 Temporal Variations in the Oxygen Regime 3.3.3.1 Seasonal Effects 3.3.3.2 Inter-tidal Differences 3.3.3.3 Intra-tidal Differences 3.3.4 Primary Production and Nutrient Dynamics 3.4 Summary ii Chapter 4 Pollution of the Mersey Estuary 4.1 Introduction 4.2 Biochemical Oxygen Demand 4.3 Ammonia 4.4 Dissolved Oxygen 4.5 Heavy Metals 4.5.1 Mercury 4.5 .2 Lead 4.5.3 Cadmium 4.5.4 Other Heavy Metals 4.6 Organic Pollutants 4.6.1 Pentachlorophenol 4.6.2 Carbon Tetrachloride 4.6.3 1,2 -Dichloroethane 4.6.4 Other Chlorinated Hydrocarbons 4.7 Historical Records of Metals in Dated Salt Marsh Sediment Cores Chapter 5 Quality status of the Mersey Estuary 5.1 Estuary Classification 5.2 Dissolved Oxygen 5.3 Nutrients 5.4 Compliance with Environmental Quality Standards (EQSs) 5.4.1 List I Dangerous Substances 5.4.2 List II Dangerous Substances Chapter 6 The biology of the Mersey Estuary 6.1 Introduction 6.2 Water Quality 6.2.1 Birds of the Mersey Estuary 6 .2 .2 Fish of the Mersey Estuary 6.2.3 Estuarine Communities of the Mersey Estuary 6.2.3.1 Biological Status of Inter-tidal Sediments 6 .2 .3 .2 Bioaccumulation Study 6.3 The Future Chapter 7 Future prospects for the Mersey Estuary 7.1 Quality Objectives for the Estuary 7.1.1 Achievement of Objectives 7.2 Improved Effluent Treatment for Industrial Discharges 7.2.1 Waste Minimisation 7.3 Recreational Activities 7.4 The Mersey Estuary Management Plan 7.5 Conclusion Bibliography 38 Glossary of Terms 39 Appendices 40 Appendix 1 : Regulations Implementing EC Directives in England and Wales 40 Appendix 2 : Dangerous Substances Surface Water Regulations, 1989 and 1992, EQSs for List 1 Substances under the Classification of Coastal Waters and Relevant Territorial Waters (DS2 and DS3) Appendix 3 : National Environmental Quality Standards for List II Metals for the Protection of Salt W ater Life 41 Appendix 4 : Bathing Water Directive 76/160/EEC, Compliance Assessment (1989 - 1994) Appendix 5 : UK Red List 42 Appendix 6 : Annex la Substances 43 List off Figures Figure 1.1: The Mersey Estuary 1 Figure 1.2: Riverine Inputs to the Mersey Estuary 2 Figure 1.3: Recreational Uses of the Mersey Estuary 6 Figure 3.1: Tide Curves in Open Sea 11 Figure 3.2: Tide Curves in the Mersey Estuary Figure 3.3: Volumes of Water Upstream of Given Points in the Estuary at High and Low Water 12 Figure 3.4: Effect of Freshwater Flow on the Distribution of Salinities 13 Figure 3.5: Average Flushing Times in the Mersey Estuary Figure 3.6: Behaviour of Dissolved Constituents during Mixing 14 Figure 3.7: Typical Observed Differences in Dissolved Oxygen between Spring and Neap Tides 15 Figure 3.8: Effect of Tidal Advection on Dissolved Oxygen Levels Figure 3.9: Typical Ammonia and Silicate Depletion Patterns during a Plankton Bloom 16 Figure 4.1: Biochemical Oxygen Demand, Mersey Estuary 17 Figure 4.2: Improvements in Water Quality at Howley Weir 18 Figure 4.3: Reductions in Load Inputs of Mercury to the Mersey Estuary from Chlor-Alkali Plants Figure 4.4: Mercury in Mersey Estuary Sediments 19 Figure 4.5: M ercury and Lead in M ersey Fish, 1 9 9 2 -9 3 Figure 4.6: River Irwell - Pentachlorophenol EQS Monitoring 20 Figure 4.7: Inputs of Pentachlorophenol to the Mersey Estuary 21 Figure 4.8: Inputs of Carbon Tetrachloride to the Mersey Estuary Figure 4.9: Inputs of 1,2-Dichloroethane to the Mersey Estuary 22 Figure 4.10: Inputs of Chloroform to the Mersey Estuary Figure 4.11: Concentrations of Metals in Widnes Warth Core Sample 1 23 Figure 4.12: Concentrations of Metals in Widnes Warth Core Sample 2 Figure 5.1: Mersey Estuary Classification 24 Figure 5.2: Dissolved Oxygen Profiles Figure 5.3: Temporal and Spatial Variations of the Major Nutrients in the Mersey Estuary, 1993 25 Figure 6.1: International and National Designations on the Mersey Estuary 27 Figure 6.2: Winter Maxima of Bird Populations on the Mersey Estuary 28 Figure 6.3: Mean Metal Concentrations found in Fish Tissue from the Mersey Estuary 30 Figure 6.4: Mercury Levels present in the Muscle Tissue of Eels taken from the Mersey Estuary and the Solway Firth 31 Figure 6.5: Distribution of Macrobenthos in different Substrata in the Mersey Estuary, May 1988 32 Figure 6.6: Metals in Nereis diversicolor in the Mersey Estuary, 1991 33 Figure 6.7: Mercury Levels in Mytilus edulis 1980 to 1991 34 List of Tables Table 1.1: The Mersey Estuary: Statistics 1 Table 3.1: Time Differences in Minutes between Local High Water and High Water at Prince's Pier 12 Table 4.1: Types of Sewage Treatment 17 Table 4.2: Biochemical Oxygen Demand Reductions through Sewage Treatment Table 4.3: Estimated Loads of Cadmium Discharged to the Estuary from Industrial Sources 20 Table 4.4: Causes for Reduced Discharges of some Heavy Metals to the Mersey Estuary Table 5.1: Mean Concentrations of List 1 Substances in the Mersey Estuary, 1993 26 Table 5.2: Mean Concentrations of List II Metals in the Mersey Estuary, 1993 List of Plates Plate 1.1: The Mersey Estuary viii Plate 1.2: Liverpool Docks, present day 3 Plate 1.3: Shell's Complex at Stanlow 4 Plate 1.4: Oil Spill, August, 1989 Plate 1.5: Eastham Locks, Manchester Ship Canal 5 Plate 4.1: ICI Runcorn, overlooking the Mersey Estuary 19 Plate 7.1: Sailing on the Mersey Estuary 37 EXECUTIVE SUMMARY 1 Introduction The Mersey Estuary is widely regarded as one of the most polluted estuaries in Europe.