Long-term changes to water levels in Thirlmere Lakes – drivers and consequences Samira Schädler A thesis in fulfillment of the requirements for the degree of Masters of Philosophy Centre for Ecosystem Science School of Biological, Earth and Environmental Science Faculty of Science University of New South Wales August 2014 ORIGINALITY STATEMENT 'I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and lingu· · ex ression is acknowledged.' S1gned 521. ~[tA t/1 ?ftJ&c Date ?,~j&J:1q Abstract Many of the world’s rivers and wetlands have degraded with alteration of flow regimes. Mostly this is due to impacts of structures (i.e. dams and weirs), but increasingly mining and access to groundwater have affected flooding regimes to wetlands. We investigated water levels within Thirlmere Lakes National Park, which are primarily filled by rainfall but interact with shallow groundwater. We focused on the three of the five lakes, with the most historical data, and compared inputs from rainfall and water levels over 113 years (1900–2012). This first step required development of three- dimensional models of the lakes, using topographic surveys. We then superimposed historical aerial photographs and ground photographs, allowing determination of water levels (1884–2012, n= 49 photographs/maps). We also investigated trends in groundwater levels (1999-2011) and created groundwater contour maps for two periods, before and after 1982, when longwall coal mining began. Rainfall and catchment inflow patterns were examined at three nearby water bodies (Avon, Warragamba and Nepean Dams), acting as ‘control sites’. There were no significant long-term trends in rainfall at the three ‘control sites’, although rainfall increased significantly at Thirlmere Lakes (1900 – 2012). There were similar evaporation patterns at all sites and inflows at the three dams had not decreased. Contrastingly, there was a severe decline in water levels at Thirlmere Lakes. The disassociation of inflows and water levels (1930 -2011) had steadily increased, especially since the 1980’s and we detected sudden drops in water levels in 1999, 2000 and 2004 in three lakes. This did not coincide with the main period of water extraction for steam engines and Picton Tuberculosis Village at Thirlmere Lakes (1884-1910). Groundwater levels in the shallow aquifer declined by up to 40m after mining commenced in 1982 and the number of groundwater bores had increased exponentially (1940-2011). Although there were no publicly available data on how much groundwater was extracted each year, the serious decline in water levels coincided with increased groundwater development and longwall mining (29 longwall panels (2010)). The changes to water levels were not climate related and so are perhaps best explained by anthropogenic impacts. Either there was considerable pumping of groundwater or longwall coal mining disrupted the groundwater aquifers, causing diversion of groundwater resources that drained Thirlmere Lakes. Or, changes could be due to a combination of these two anthropogenic factors. The implications are significant for the ecological character of the Thirlmere Lakes. There are many affected obligate aquatic species or species reliant on wet habitats, including five species of waterbirds (Australasian bittern i Botaurus poiciloptilus, Australian painted snipe Rostratula australis, great egret Ardea alba, cattle egret Ardea ibis, and Latham’s or Japanese Snipe Gallinago hardwickii) one fish species (Macquarie perch Macquaria australasica), two frog species (giant burrowing frog Heleioporus australiacus, Littlejohn’s tree frog Litoria littlejohni) and two plant species (smooth bush pea Pultenaea glabra, Kangaloon sun orchid Thelymitra Kangaloon) that are also listed as threatened. There are serious implications for governments and their responsibilities for managing the values of Thirlmere Lakes National Park along with the Blue Mountains World Heritage Area of which it is a part. These major changes in flooding regimes to Thirlmere Lakes will continue to degrade the National Park, its ecological, cultural and recreational values. ii Acknowledgements There were times I did not believe I would finish this degree and I am grateful for all the people who helped me get over the finishing line. I cannot express how thankful I am for all the support and guidance of my supervisor Richard Kingsford. Thank you Richard for giving me the opportunity to do this research project; thank you for your expertise and patience; thank you for letting me take a break when I was ill; thank you for all the time and effort you have devoted to this project and the countless revisions of my writing. I would also like to thank my Co-Supervisor Scott Mooney for sharing knowledge and data. I also particularly thank David Edwards who spent many frustrating hours in the field and helped me convert the survey data into topographic maps. Bryce Kelly shared his great knowledge of groundwater flow and how to detect changes in these complex systems. I would also like to thank the NSW National Parks and Wildlife Service, especially Ben Owers for sharing important local knowledge and getting access to the site. I also thank Peter Briggs from the Australian Water Availability Project and the Sydney Catchment Authority for access to crucial data on rainfall, evaporation and inflows as well as Philip and Steven Pells for sharing data on water levels at Thirlmere Lakes. I could not have done this project without all the volunteers who helped with the survey of the Thirlmere Lakes and have spent many hours in the rain, mud and thick undergrowth. A special thanks to Jai and Nathan who volunteered their time and came out with me to Thirlmere Lakes, not just once but many times. I am also grateful for all the help I received from the staff at the National Library of Australia, the State Library of New South Wales and the State Records Authority of New South Wales when trying to locate historical documents on Thirlmere Lakes. The members of the Australian Railways Historical Society NSW Division helped me find out how much water steam trains used. I am also enormously grateful for all the colleagues from the Centre for Ecosystem Science, especially Sharon Ryall for her support in all things and Rachel, Sam, Jo, Sylvia, Celine and Andrew for being great friends. Thank you all for the fun times, chats, humorous and serious, for helping with fieldwork and for sharing all your knowledge. I am grateful for the financial support from the Liechtenstein Government that allowed me to study in a unique country. iii Love to my family and friends supporting me from the other side of the globe and always believing in me. And finally to Marc for being at my side through all the ups and downs and for being awesome. iv Table of Contents Abstract i Acknowledgements iii CHAPTER 1 - INTRODUCTION 1 CHAPTER 2 - METHODS 6 2.1. Study Site 7 2.2. Rainfall and evaporation 10 2.3. Water levels Thirlmere Lakes 12 2.3.1. Water extraction 18 2.4. Groundwater 19 2.5. Other sites 19 CHAPTER 3 - RESULTS 21 3.1. Bathymetry 22 3.2. Abiotic drivers - rainfall patterns, 1900-2013 25 3.3. Abiotic drivers – inflows 27 3.4. Abiotic drivers – evaporation patterns, 1900-2013 29 3.5. Water extraction from Thirlmere Lakes 32 3.6. Groundwater 32 3.7. Water levels at Thirlmere Lakes 35 CHAPTER 4 - DISCUSSION 39 4.1. Conclusion 44 REFERENCES 46 APPENDIX 1 - IMAGERY 52 APPENDIX 2 - EPBC ACT PROTECTED MATTERS REPORT 55 v Chapter 1 Introduction Chapter 1 - Introduction Wetlands continue to be lost, degraded and altered globally, more than other ecosystems (Millennium Ecosystem Report 2005). This reflects increasing human populations and economic development, associated with growing demand for food production, energy and water, mediated by climate change (Millennium Ecosystem Report 2005; Vörösmarty et al. 2010; Palaniappan & Gleick 2011; Bogardi et al. 2012; Junk 2012). The critical factor for all wetlands is the maintenance of a natural flow regime, including quantity, variability and quality (Mitsch & Gosselink 2000). Natural flooding regimes are altered by flow interception, degrading wetlands and affecting dependent biodiversity (Bunn & Arthington 2002; Arthington & Pusey 2003; Nilsson et al. 2005a; Kingsford 2011; Watts 2011). Dams, weirs and direct pumping of water from rivers, wetlands and groundwater aquifers ubiquitously impact (Bernadez et al. 1993; Elmore et al. 2006) on freshwater ecosystems (Kingsford & Thomas 2004; Nilsson et al. 2005; Kingsford et al. 2006; Vörösmarty et al. 2010). Increasingly, there is also recognition of the impacts of mining on freshwater ecosystems, either through direct or indirect pollution, or alteration of surface and groundwater flow regimes supplying wetland systems (Whitfield 1988; Dawkins 1999; Itasca 2002; Booth 2006; Booth 2007; McNally & Evans 2007; Jankowski et al. 2008; Marandi et al. 2013). Concerns about the adverse effects of coal mining on the environment, especially rivers and wetlands continue to increase with the expansion of mining (Kay et al. 2006; Krogh 2007). Australia’s coal mining industry makes up 1.8% (2011/2012) of gross value added (Davidson & de Silva 2013) and continues to grow. Thirlmere Lakes are in the Hawkesbury-Nepean Catchment (Fig. 1), affected by mining, agriculture, river regulation and urbanisation. Tahmoor Colliery, adjacent to Thirlmere Lakes National Park has completed mining of 29 longwall panels by 2010, the closest being only 600m from the lakes (Russell et al.