Influence of urban expansion on groundwater recharge in southeast Melbourne, Australia. A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy Ben Hall BSc – Applied Geology (RMIT University) BSc (Hons) - Geophysics (Curtin University) School of Engineering College of Science, Engineering and Health RMIT University August 2018 DECLARATION I certify that except where due acknowledgement has been made, the work is that of the author alone; the work has not been submitted previously, in whole or in part, to qualify for any other academic award; the content of the project is the result of work which has been carried out since the official commencement date of the approved research program; any editorial work, paid or unpaid, carried out by a third party is acknowledged; and, ethics procedures and guidelines have been followed. I acknowledge the support I have received for my research through the provision of an Australian Government Research Training Program Scholarship. Ben Hall 25 May 2018 ii ACKNOWLEDGEMENTS Without doubt, this thesis would not have been completed without the vision, patience, good humour, encouragement, critical feedback and insight of my supervisor Dr Currell. Thank you Matt for all your help and support. Thank you also to Assoc. Prof. John Webb for providing high level input to research, thesis structure and editorial review. Funding for this research was provided by Melbourne Water and this, together with input and support from Judy Blackbeard, Micah Pendergast and Sarah Gaskill is greatly appreciated. I also benefited from tremendous help from RMIT staff and students during my research and thanks to Ramesh Dilipsingh, Steven Lee, Emily Hepburn, Josh Dean and Justin Scicluna for their assistance with fieldwork and research development. Thank you to La Trobe University and Monash University for use of their analytical laboratories and assistance from Rachelle Pierson, Farah Ali and Mario Gatineau. The Australian Institute of Geoscientists generously provided a travel scholarship to support conference attendance. The following organisations and people provided access to data that added depth and rigour to the research: Victorian Department of Environment, Land, Water and Planning (Mick Hoban). Southern Rural Water (Elissa McNamara and Liam Murphy). Royal Botanic Gardens Cranbourne (Warren Worboys). And of course, a big thank you to Jo, Liam, Asha and Audrey. I am not the person I am without them. iii CONTENTS Table of Contents Abstract ................................................................................................................................................... 6 1 Introduction .................................................................................................................................... 8 1.1 Urbanisation and groundwater recharge ............................................................................... 8 1.2 Research Objectives ................................................................................................................ 9 1.3 Thesis Outline ........................................................................................................................ 11 2 Previous scientific investigations of groundwater recharge and the impacts of urbanisation .... 14 2.1 Global population growth and urbanisation ......................................................................... 14 2.2 The influence of land use change on the hydrologic system ................................................ 15 2.3 Groundwater recharge.......................................................................................................... 18 2.4 Changes in groundwater flow dynamics from urbanisation ................................................. 19 2.5 Changes in groundwater recharge rates resulting from urbanisation ................................. 22 2.6 Changes in water quality from urbanisation ........................................................................ 24 2.7 Determining changes in recharge from urbanisation ........................................................... 30 2.8 Managing impacts to groundwater from urbanisation ........................................................ 34 3 Land use change, geology and hydrogeology of Western Port Basin ........................................... 37 3.1 Landscape and land use ........................................................................................................ 37 3.2 Geology ................................................................................................................................. 48 3.3 Hydrogeology ........................................................................................................................ 57 4 Methods ........................................................................................................................................ 67 4.1 Monitoring bore installation ................................................................................................. 67 4.2 Estimation of Hydraulic Conductivity .................................................................................... 69 4.3 Groundwater sampling ......................................................................................................... 71 4.4 Rainfall .................................................................................................................................. 75 4.5 Water level and salinity observations ................................................................................... 75 4.6 Soil Moisture ......................................................................................................................... 77 4.7 Data mining & integration .................................................................................................... 78 5 Results ........................................................................................................................................... 80 5.1 Geology and updated hydrogeological conceptualisation ................................................... 80 5.2 Hydraulic Conductivity .......................................................................................................... 87 5.3 Groundwater Salinity ............................................................................................................ 89 5.4 Major ions and physico-chemical parameters ...................................................................... 92 5.5 Radiocarbon (14C), stable isotopes of carbon (δ13C) and Tritium (3H)................................... 99 5.6 Aquifer renewal rates ......................................................................................................... 102 i CONTENTS 5.7 Stable Isotopes of water ..................................................................................................... 107 5.8 Rainfall ................................................................................................................................ 110 5.9 Time series water level and electrical conductivity data .................................................... 113 5.10 Soil moisture monitoring .................................................................................................... 116 6 Regional Recharge Dynamics ...................................................................................................... 120 6.1 Introduction ........................................................................................................................ 120 6.2 Rates of recharge ................................................................................................................ 121 6.3 Factors controlling groundwater recharge ......................................................................... 132 6.4 New conceptual understanding of regional recharge processes........................................ 139 6.5 Implications for water resource and land use planners ..................................................... 141 7 Influence of constructed wetlands on groundwater recharge ................................................... 143 7.1 Linsell Boulevard Constructed Wetland .............................................................................. 143 7.2 Conceptual Model for Surface Water – Groundwater Interaction of Linsell Boulevard Constructed Wetland ...................................................................................................................... 153 7.3 Potential additional focussed recharge .............................................................................. 157 7.4 Implication for water resource and land use planners ....................................................... 160 8 Conclusions ................................................................................................................................. 168 8.1 Summary of findings / Research aims & contributions ...................................................... 168 8.2 Effectiveness of various techniques for characterising recharge ....................................... 170 8.3 Recommendations for future research ............................................................................... 173 9 References .................................................................................................................................. 176 Appendices Appendix A: Bore Construction Logs ……………………………………………………………………………………………..199 Appendix B: Hydraulic