CSIRO LAND and WATER Ecological History of the Tuggerah Lakes Final Report By Anthony Scott CSIRO Land and Water, Canberra Technical Report 18/99 June 1999 &6,52/$1'DQG:$7(5 (FRORJLFDO+LVWRU\RIWKH7XJJHUDK/DNHV )LQDO5HSRUW %\$QWKRQ\6FRWW -XQH 3URGXFHGE\&6,52/DQGDQG:DWHUDQG6DLQW\ $VVRFLDWHV IRU:\RQJ6KLUH&RXQFLO &6,52/DQGDQG:DWHU&DQEHUUD 7HFKQLFDO5HSRUW-XQH Acknowledgements I would like to thank the residents of Wyong Shire who provided much of the information collected for this report. It was a pleasure to meet so many friendly people and to be given the opportunity of recording their memories of the Tuggerah Lakes. In many instances they also lent me their old photos, newspaper clippings and maps. Their enthusiasm and support for this project is something I will always remember. I would also like to thank Wyong Shire Council for their financial support and in particular Greg Walkerden, Danny Roberts and Sharon Cummins. Both their technical assistance and their patience at what seemed to be a never-ending task was greatly appreciated. Also Geoff Sainty and Kathryn Duchatel of Sainty & Associates for project management and technical contributions to the project, and Phil Morley of the Wyong District Museum & Historical Society who spent a great deal of time searching through their records for relevant documents and photos. The report was reviewed by Graeme Batley (CSIRO Energy Technology), Ann Gronell (CSIRO Division of Marine Research), Ross Higginson (NSW EPA), Gary Henry (NSW Fisheries), Phil Morley (Wyong Historic Society), Ian Webster (CSIRO Land & Water) , Robert King (School of Biological Science, University of NSW), Alan Morris (NSW National Parks & Wildlife Service), Glenn Sharrock (Delta Electricity), Ken Grantham and Terry Gibbs (Wyong Shire Council), Addresses; Anthony Scott CSIRO Land and Water GPO Box 1666 Canberra ACT 2601 Geoff Sainty Sainty and Associates PO Box 1219 Potts Point, NSW 2011 Greg Walkerden Environmental Systems Manager Wyong Shire Council PO Box 20 Wyong NSW 2259 Front cover photo; Constructing the first ‘Long Jetty’, circa 1915. (supplied by Wyong Historical Society) 2 Table of Contents ACKNOWLEDGEMENTS................................................................................................................................................2 SUMMARY.................................................................................................................................................................4 1 INTRODUCTION ..............................................................................................................................................6 1.1 OBJECTIVE ....................................................................................................................................................6 1.2 INTERPRETATION OF HISTORICAL INFORMATION ...........................................................................................6 1.3 THE TUGGERAH LAKES .................................................................................................................................7 2 SETTLEMENT OF THE TUGGERAH LAKES ............................................................................................9 2.1 ABORIGINAL SETTLEMENT ............................................................................................................................9 2.2 THE FIRST EUROPEAN SETTLERS (1820S – 1870S).........................................................................................9 2.3 DEVELOPMENT ACCELERATES AFTER THE OPENING OF THE RAILWAY (1880S – 1950S)..............................10 2.4 URBAN DEVELOPMENT (1960S – 1990S) .....................................................................................................11 3. AQUATIC PLANTS AND ALGAE................................................................................................................13 3.1 AQUATIC PLANTS ........................................................................................................................................13 3.2 ALGAE.........................................................................................................................................................16 3.3 SEAGRASS AND MACROALGAE – GETTING THE BALANCE RIGHT..................................................................17 3.4 HISTORY OF ‘WEED’ GROWTH IN THE TUGGERAH LAKES............................................................................17 3.5 WEED GROWTH – LONG TERM CHANGES .....................................................................................................27 3.6 EUTROPHICATION IN COASTAL AREAS OF AUSTRALIA.................................................................................30 4. CHANGES ALONG THE SHORELINE.......................................................................................................33 5 AQUATIC FAUNA ..........................................................................................................................................36 5.1 FINFISH – ANECDOTAL EVIDENCE................................................................................................................36 5.2 FINFISH – ASSESSING THE CATCH STATISTICS..............................................................................................39 5.3 PRAWNS – ANECDOTAL EVIDENCE ..............................................................................................................46 5.4 PRAWNS – ASSESSING THE CATCH STATISTICS.............................................................................................47 5.5 ASSESSING THE RECREATIONAL CATCH OF FINFISH AND PRAWNS ...............................................................48 5.6 OTHER MARINE SPECIES ..............................................................................................................................49 6 NUTRIENTS IN THE TUGGERAH LAKES ...............................................................................................52 6.1 SOURCES OF NUTRIENTS ..............................................................................................................................52 6.2 CHEMICAL AVAILABILITY............................................................................................................................52 6.3 NUTRIENT LIMITATION ................................................................................................................................54 6.4 NUTRIENT BUDGET FOR THE TUGGERAH LAKES..........................................................................................55 6.5 SEDIMENT AND NUTRIENTS FROM THE UPPER CATCHMENT .........................................................................57 6.6 SEWAGE POLLUTION....................................................................................................................................58 6.7 URBAN STORMWATER .................................................................................................................................60 7 OPENING OF THE ENTRANCE CHANNEL .............................................................................................62 8 MUNMORAH POWER STATION................................................................................................................65 8.1 IMPACTS OF THE POWER STATION ...............................................................................................................65 9 WATERBIRDS.................................................................................................................................................74 10 OTHER IMPACTS ......................................................................................................................................78 11 CONCLUSIONS...........................................................................................................................................79 REFERENCES .........................................................................................................................................................81 APPENDIX 1 SOME NOTES ON CALCULATING NUTRIENT LOADS......................................................85 3 Summary The Tuggerah Lakes are on the Central Coast of NSW and consist of three interconnected coastal lagoons, Lake Munmorah, Budgewoi Lake and Tuggerah Lake. There has been rapid urban development over the last 20-30 years and this has resulted in a number of environmental pressures being placed on the lakes’ ecology. One of the problems facing the managers of the Tuggerah Lakes is the lack of scientific data available that provides an indication of what the lakes were like in pre-development times. To overcome this problem, historical information was collected to provide an insight into the long term ecological changes of the lakes. This included historical documents, old newspapers and anecdotal records from residents who have lived in the area for up to 90 years. The historical information was then combined with more recent scientific studies of the lakes to provide a better understanding of the ecological changes to the lakes since European settlement. Pressures and impacts The evidence collected suggests that European settlement has placed a number of pressures on the ecology of the lakes, including; • Rapid urban development around the lakes, with associated problems with sewage and stormwater disposal, • Operation of a coal-fired power station which used lake water for cooling purposes, • Land clearing and logging of the upper catchment, and