Reservoir Released Waves as a Transient Riverine Pollution Mitigation Tool An examination of the feasibility of using waves of water released from a reservoir as a response to pollution spills. Simon DeSmet Submitted in accordance with the requirements for the degree of Doctor of Philosophy The University of Leeds School of Geography December 2014 - ii - The candidate confirms that the work submitted is his/her own and that appropriate credit has been given where reference has been made to the work of others. This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. © 2014 The University of Leeds and Simon DeSmet - iii - Acknowledgements I have depended on God and faith to carry me though the preparation of this Thesis. A number of individuals have been of great assistance over the past few years. Firstly my two primary supervisors Dr Paul Kay and Dr Jonathan Carrivick have been immensely patient, taught me to write properly, vetted my ideas and have provided great wisdom and experience. Technical assistance with the Fluent software was provided by Dr Andy Sleigh and Dr Carl Gikeson. Access to the SORBY flume facility and input on ideas for the flume study were given by Dr Daniel Parsons and Dr Gareth Keevil. For help in designing the field study and collecting the data I would like to thank David Ashley, Rachel Gasior, Dr Pengfei Li, Dr Ben Gillespie and numerous individuals a the Environment Agency. Additionally I owe a thanks to Rachel Homer for assistance with statistics. Yorkshire Water Services have provide funding, site access, and industrial experience that has been invaluable. In particular I owe thanks to Mark Tinsdeall, James Kitson, David Townend, Joanne Baxter, Simon Wolmersley, and Jenny Banks. Finally Jacqui Manton, Jacqui Brown, Dr John Gibbons, Dr David Romero, Dr Balazs Kulik, Dr Gemma Dooling and Dr Carol White have all supported me in innumerable ways. 7 All the rivers run into the sea; yet the sea is not full; unto the place from whence the rivers come, thither they return again. Ecclesiastes 1:7 - iv - Abstract Pollution spills are a serious threat to rivers causing fish kills, and lasting damage to the biological systems of rivers. At present financial penalties are used to deter such incidents but no mitigation system exists. A multiple method approach involving a hydrological and water chemistry based field study, a flume tank experiment, a computer fluid dynamics model and a 1D flow model was under taken to examine the feasibility of using a wave of water released from a reservoir to dilute pollution spills. Nine waves were released from reservoirs on three different catchments. Water quality was measured downstream of sewage treatment works and the progress of the wave was tracked down the river with gauges. Additionally in one experiment a slug of rhodamine dye was released into the river ahead of a wave. To understand the impact of a wave on mixing processes within the water column, in particular longitudinal dispersion, a series of flume tank and computer fluid dynamics experiments were ran. In both experiment sets a wave was released from one end of a tank and a slug of either rhodamine dye, or tracked particles was released mid tank, the interaction between the wave and the dye was then captured as footage and analysed. Across the three sets of experiments waves were found to move significantly faster than the baseflow with mean velocities ranging between 0.86ms-1 1.63ms-1. In the Holme River a dye slug would be caught within 3 hours and 46 minutes. Catch up times and response times were both demonstrated with a dye test and estimated with a 1D model providing management focused results previously unreported in the literature. Dilution of water quality parameters including NH4 and conductivity was recorded during wave passage at the sewage treat works outflows in the majority of experiments. Peak dilutions of 59% for NH4 and 58% for conductivity were recorded. An increase in longitudinal dispersion with wave magnitude was observed in the computer fluid dynamics model but unclear within the flume tank. - v - Table of Contents Chapter 1. Introduction ................................................................................. 1 1.1 Thesis Structure .................................................................................... 1 1.2 Terminology ........................................................................................... 2 1.3 Key Questions ....................................................................................... 3 1.4 Aims ...................................................................................................... 6 Chapter 2. Literature Review ........................................................................ 7 2.1 The Importance of Water Quality ........................................................... 7 2.2 The Nature of Pollution .......................................................................... 8 2.3 The Focus of this Study: Pollution ....................................................... 12 2.4 The Conceptual Solution ..................................................................... 18 2.5 Conclusion........................................................................................... 22 Chapter 3. Reservoir Release Experiments: The Field Study Approach 23 3.1 Introduction .......................................................................................... 23 3.2 Literature ............................................................................................. 23 3.3 Aims .................................................................................................... 26 3.4 Methodology ........................................................................................ 27 3.5 Results ................................................................................................ 46 3.6 Discussion ........................................................................................... 74 3.7 Conclusions ......................................................................................... 82 Chapter 4. The Flume Study Approach ..................................................... 83 4.1 Introduction .......................................................................................... 83 4.2 Literature and Background .................................................................. 83 4.3 Aims and Objectives ............................................................................ 87 4.4 Methodology ........................................................................................ 89 4.5 Results .............................................................................................. 100 4.6 Discussion ......................................................................................... 119 4.7 Conclusion......................................................................................... 126 Chapter 5. Computer Fluid Dynamics Approach .................................... 128 5.1 Introduction ........................................................................................ 128 5.2 Literature ........................................................................................... 128 5.3 Aims .................................................................................................. 132 5.4 Methodology ...................................................................................... 133 5.5 Results .............................................................................................. 146 5.6 Discussion ......................................................................................... 157 - vi - 5.7 Conclusion ......................................................................................... 162 Chapter 6. Discussion and Application.................................................... 164 6.1 Key Question 1; How quickly can a wave of water released from a reservoir catch a slug of polluted water? ............................................ 164 6.2 Key Question 2; How much dilution can be achieved? ....................... 166 6.3 Key Question 3, What Mixing Processes Occur When a Wave Catches Polluted Water? ................................................................... 169 6.4 The 1D model .................................................................................... 171 6.5 Key Lessons of the Work ................................................................... 175 6.6 Challenges to using reservoirs as a mitigation tool ............................. 181 6.7 Conclusion and Evaluation ................................................................. 185 - vii - List of Tables Table 3-1 Rivers, and reservoirs used either in this study, or within the literature. Release is the maximum release magnitude recorded for the reservoir in question. Distance to measurement is the distance between the reservoir and the farthest downstream water quality measurement site used in each study. ..................................................... 28 Table 3-2. The reservoir release program employed in the current study. Program refers to the release design and purpose. An explanation of each is given below. .............................................................................. 35 Table 3-3. Water quality parameters on the YSI sonde device and the instrumentation used to measure them in the current study.