Durham E-Theses Water quality in estuarine impoundments Wright, Julian Paul How to cite: Wright, Julian Paul (2002) Water quality in estuarine impoundments, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/4027/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk AK; eq xov avxov TCOTafiov OVK dv 8|j.pairiq. (You can't step twice into the same river.) Heraclitus, in Plato "Cratylus". Water Quality in Estuarine Impoundments Julian Paul Wright The copyright of this thesis rests with the author. No quotation from it should be published without his prior written consent and information derived from it should be acknowledged. I 8 JUH 2003 Thesis submitted in accordance with the regulations for the degree of Doctor of Philosophy in the University of Durham, Department of Geological Sciences, 2002. Abstract Water Quality in Estuarine Impoundments Julian Paul Wright The impounding of estuaries is currently a popular approach to urban regeneration in the UK, with barrages constructed (Tees, Wansbeck, Tawe, Cardiff Bay, Lagan and Clyde) or proposed (Usk, Loughor, Neath, Hayle, Avonmouth and Ipswich) nationwide. Impounding fundamentally alters the dynamics of estuaries with consequences in terms of sedimentation patterns and rates, ecology, flooding, groundwater, etc. This thesis presents the findings from research into the effects of impounding on estuarine water quality. A series of surveys of a range of physical and chemical parameters were carried out within four estuaries representing the complete range of tidal modification by barrage construction. Internal versus external controls on water quality are distinguished. General water quality in estuarine impoundments is good, but significant problems occur where water bodies show entrenched density stratification, with anoxia and associated increases in ammonia and metal concentrations developing. Stratification related problems are worse in partial than total tidal exclusion impoundments (although a higher rate of tidal overtopping shortens the isolation periods of deep anoxic waters), and low water quality at depth is observed over the majority of the year. The potential for eutrophication is increased by barrage construction, although phosphorus (generally the limiting nutrient) is shown to be catchment sourced, with internal cycling from sediment insignificant. Sediment thickness is shown not to be a control on water quality, although sediment build-up over time eventually leads to a loss of amenity value. Sterol fingerprints are used to identify sewage inputs to the impoundments. Advice for barrage planners and designers is given, including the exclusion and removal of saline water, provision of destratification/aeration devices, control of nutrient inputs, and modelling of sediment loads and deposition. This study has shown that catchment management is fundamental in the sustainability of estuarine impoundments. Acknowledgements I would like to thank my supervisor, Fred Worrall, for his tireless support throughout this research. Fieldwork would not have been possible without the assistance of Jens Lamping, Bernard McEleavey, Steve Richardson, Ruth Stadnik, Anna Reed, Mareike Leiss, John Collins, Heather Handley and Alex Gardiner, all of whom endured variable weather and erratic boat driving with stoicism. Thanks go to Norman Howitt of the Cambois Rowing Club for allowing storage of the RV, Terry Gamick of Wansbeck District Council for discussions on management of the Wansbeck impoundment, and John Dickson of British Waterways for information on management of the Tees Barrage. I would like to thank all those who made my stay in Swansea so enjoyable and productive, particularly Hugh Morgan and Sam Taylor of Swansea City Council. The principles and operation of the ICP machines were taught with patience by Chris Ottley of the Department of Geological Sciences, University of Durham. Frank Davies and Derek Coates of the Department of Geography assisted with the particle size analyses, and many thanks go to Brian Whitton, Robert Baxter and the members of laboratory 9 of the Department of Biological Sciences for allowing use of the nutrient autoanalyser. Alison Reeve of the University of Dundee, Martin Jones of the University of Newcastle and particularly Marie Russell of the Department of Geography, University of Durham, helped with the analyses of sterol biomarkers. Many from the Environment Agency of England and Wales provided useful data, comment and discussion, including Michael Stokes, Richard Vaughan, Jeff Hoddy, Eddie Douglas and Roger Inverarity. Excellent and varied logistical support was given by the staff of the Department of Geological Sciences, University of Durham. This work was supported financially by EPSRC Grant GR/M 42299. Finally I would like to thank all those who have provided friendship and support during my time in Durham. Particular mention must go to my family, Rebecca, Mrs. Grant, Dr. Mark, Dave and Hannah, the BC Boys, the Graduate Society Hockey Club and the postgraduate members of St. John's College and the Department of Geological Sciences. HI I confirm that no part of the material presented in this thesis has previously been submitted by me or any other person for a degree in this or any other university. In all cases material from the work of others has been acknowledged. The copyright of this thesis rests with the author. No quotation from it should be published without prior written consent and information derived from it should be acknowledged. Signed: Date: O] /o/o::s IV Contents Title page i Abstract ii Acknowledgements iii Declaration iv Contents v 1 Introduction l 1.1 Outline of the problem 1 1.2 Research objectives and structure of the thesis 1 1.3 Introduction to the study areas 3 1.3.1 Estuaries studied 3 1.3.2 The Tees Estuary 4 1.3.2.1 Tees River 4 1.3.2.2 Tees Barrage 6 1.3.3 The Wansbeck Estuary 8 1.3.3.1 Wansbeck River 8 1.3.3.2 Wansbeck Barrage 8 1.3.4 The Tawe Estuary 10 1.3.4.1 Tawe River 10 1.3.4.2 Tawe Barrage 10 1.3.5 The Blyth Estuary 12 1.3.5.1 Blyth River 12 1.3.5.2 Blyth Estuary 13 1.4 Water quality in estuarine impoundments; definitions and review 13 of research 1.4.1 Types of barrage 13 1.4.1.1 Tidal power barrages 14 1.4.1.2 Flood protection barrages 14 1.4.1.3 Water storage barrages 15 1.4.1.4 Urban redevelopment and amenity barrages 15 1.4.2 Water quality issues 16 1.4.2.1 Stratification 16 1.4.2.2 Dissolved oxygen 16 1.4.2.3 Sedimentation 17 1.4.2.4 Eutrophication 17 1.4.2.5 Remediation schemes 18 1.4.3 Summary of related issues 19 1.4.3.1 Ecology 19 1.4.3.2 Fisheries and fish passes 20 1.4.3.3 Groundwater 20 1.4.3.4 Flooding 21 1.4.3.5 Amenity use 22 1.4.3.6 Costs and benefits 22 Water Quality Surveys 24 2.1 Survey desien 24 2.1.1 Experimental design 24 2.1.2 Estuaries studied 24 2.1.3 Sampling stations 25 2.1.4 Depths sampled 29 2.1.5 Replicates 30 2.1.6 Dates sampled and hypothesis testing 30 2.2 Sampling procedure 32 2.2.1 Safety precautions 32 2.2.2 Procedure 32 2.3 Water quality parameters measured 34 2.3.1 Introduction 34 2.3.2 Physical/chemical 35 2.3.2.1 Dissolved oxygen 35 2.3.2.2 Biochemical oxygen demand 35 2.3.2.3 pH 36 2.3.2.4 Alkalinity 36 2.3.2.5 Eh 37 2.3.2.6 Conductivity 37 2.3.2.7 Temperature 38 2.3.2.8 Transparency 38 2.3.2.9 Total Suspended Solids 38 2.3.3 Nutrients 38 vi 2.3.3.1 Nitrogen 39 2.3.3.2 Phosphorus 40 2.3.3.3 Silicon 41 2.3.4 Major elements 41 2.3.4.1 Sodium 41 2.3.4.2 Potassium 42 2.3.4.3 Magnesium 42 2.3.4.4 Calcium 42 2.3.4.5 Sulphur 42 2.3.5 Minor and trace metals 43 2.3.6 Flow 44 2.4 Analytical methods 46 2.4.1 Dissolved oxygen 46 2.4.2 pH 47 2.4.3 Eh 48 2.4.4 Conductivity 49 2.4.5 Temperature 50 2.4.6 Transparency 51 2.4.6 Alkalinity 52 2.4.7 Total suspended solids 52 2.4.8 Biochemical oxygen demand 53 2.4.9 Nitrate, ammonia and phosphate 54 2.4.9.1 Nitrate 55 2.4.9.2 Ammonia 55 2.4.9.3 Phosphate 56 2.4.10 Metals and non-metals by ICP-OES 56 2.5 Overview of data collected during the water quality surveys 61 2.5.1 Data handling and quality assurance 61 2.5.2 Fulfilment of experimental design 61 2.5.2.1 Rivers/estuaries studied 62 2.5.2.2 Dates sampled 62 2.5.2.3 Sites and distances sampled 62 2.5.2.4 Depths sampled 62 2.5.3 Data summary 63 2.5.3.1 One-way ANOVA between estuaries 63 vii 2.5.3.2 Graphical presentation of data as boxplots 65 2.5.3.3 Tidal height and overtopping 66 2.5.3.4 River flow 66 2.5.3.5 Temperature 68 2.5.3.6 Dissolved oxygen 69 2.5.3.7 BOD 72 2.5.3.8 pH 73 2.5.3.9 Alkalinity 74 2.5.3.10 Conductivity 74 2.5.3.11 Eh 77 2.5.3.12 Transparency 78 2.5.3.13 TSS 79 2.5.3.14 Nutrients 80 2.5.3.15 Major elements 83 2.5.3.16 Minor and trace metals 86 Seasonal Effects on Water Quality 89 3.1 Introduction 89 3.2 Tees 89 3.2.1 Temperature 90 3.2.2 Dissolved oxygen 91 3.2.3 BOD 96 3.2.4 pH 100 3.2.5 Alkalinity 103 3.2.6 Conductivity 105 3.2.7 Transparency