BAYWIDE WATER QUALITY MONITORING PROGRAM MILESTONE REPORT NO.6 SEPTEMBER 2010 BAYWIDE WATER QUALITY MONITORING PROGRAM — MILESTONE REPORT NO. 6 EXECUTIVE SUMMARY Port Phillip Bay (PPB) is a large, shallow, almost landlocked bay under the influence of substantial urbanisation. Maintaining the key environmental processes of PPB is essential for sustainability. Water quality is important to a variety of assets, values and uses of PPB. There are several factors that can influence water quality in PPB, including: • Exchanges between the water column, sediment and atmosphere • Tidal flushing from Bass Strait • Sediment, nutrient and toxicant loads in freshwater inflows, particularly from the Yarra River • Discharges from industry and other users. These influences are reflected in the spatial and temporal variability of water quality parameters such as toxicants, nutrients and turbidity. This is the context for the Water Quality Baywide Monitoring Program (WQBMP) associated with the Channel Deepening Project (CDP). The WQBMP has been monitoring water quality in PPB on a monthly basis since November 2007, three months prior to the commencement of dredging activities for the CDP. Generally, the results of water quality monitoring in PPB over this period are within natural variability and the expected effects of the CDP, as determined by historical range and associated statistical analyses. For the most part, water quality was within accepted guidelines. EPA identified no major areas of concern from assessment of the six month reporting period, January – June 2010. The results reported here are consistent with an understanding of water quality in PPB derived from earlier studies and other monitoring programs. Water quality in PPB continues to be influenced by rainfall and associated catchment inputs. In particular, the large rainfall event in March 2010 resulted in an inflow of nutrients, particularly nitrogen from the catchments. Phytoplankton biomass was highest along the western shores and north of the Bay refecting this distribution of available nutrients. The results from this and other programs designed to monitor the health of PPB have indicated that changes in key environmental processes and assets are within the natural variability expected for PPB. Water quality throughout PPB remains as high as it has been for at least the past 20 years and is sufficient for maintaining assets and beneficial uses. 2 Table of Contents Baywide water Quality monitoring Program.........................................................................1 Milestone REport No.6.........................................................................................................1 September 2010 ..................................................................................................................1 Executive Summary.............................................................................................................2 1. Introduction...................................................................................................................9 2. Discussion ..................................................................................................................12 3. Conclusions ................................................................................................................23 4. References .................................................................................................................25 Appendix 1 - Background...................................................................................................30 Appendix 2 - Methods........................................................................................................33 Appendix 3 - Results..........................................................................................................44 Appendix 4 - QA/QC data and discussion........................................................................101 Appendix 5 - Results outside of natural/expected variability............................................104 Appendix 6. - Summary Statistics (July 2009 – June 2010).............................................108 List of Tables Table A1.1 SEPP (WoV) objectives and ANZECC trigger values......................................32 Table A2.1 Locations and corresponding SEPP (WoV) segments ....................................33 Table A2.2 EWMA control limits for listed water quality parameters..................................37 Table A2.3 Shewhart control limits for listed water quality parameters..............................38 Table A3.1 Field sampling dates and weather conditions (January – June 2010) .............44 Table A3.2 Summary of Exception Reports (January – June 2010) ..................................45 Table A3.3 Summary of exceedence of control limits for physico-chemical data and nutrients (January – June 2010) ........................................................................................53 Table A3.4 Temperature Stratification in PPB (January – June 2010)...............................59 Table A5.1 PoMC/EPA Assessment (January – June 2010) ...........................................105 Table A6.1 Yarra River at Newport summary statistics – Schedule F7 Yarra Port Segment Objectives........................................................................................................................108 Table A6.2 Yarra River at Newport summary statistics – Schedule F6 Hobsons Segment objectives.........................................................................................................................109 Table A6.3 Hobsons Bay summary statistics...................................................................110 Table A6.4 Corio Bay summary statistics ........................................................................111 Table A6.5 Long Reef summary statistics........................................................................112 Table A6.6 Central Bay summary statistics .....................................................................113 Table A6.7 POM DMG summary statistics.......................................................................114 Table A6.8 Patterson River summary statistics ...............................................................115 Table A6.9 Dromana summary statistics .........................................................................116 Table A6.10 Middle Ground Shelf summary statistics .....................................................117 Table A6.11 Sorrento Bank summary statistics ...............................................................118 Table A6.12 Popes Eye summary statistics.....................................................................119 3 BAYWIDE WATER QUALITY MONITORING PROGRAM — MILESTONE REPORT NO. 6 List of Figures Figure 1 Water Quality Monitoring Program sampling sites in PPB ...................................11 Figure A2.1 DPI Nutrient cycling continuous in-situ monitoring sites .................................40 Figure A2.2 Examples of IMOS shipborne data sampled from the Spirit of Tasmania. .....41 Figure A2.3 EPA and PoMC Beach monitoring sites .........................................................42 Figure A3.1 Victorian rainfall deciles Jan – June 2010 ......................................................47 Figure A3.2 Victorian rainfall deciles July – Dec 2009 .......................................................47 Figure A3.3 Victorian rainfall deciles Jan - June 2009 .......................................................48 Figure A3.4 Yarra River rainfall, river flow and storm events (January – June 2010) ........49 Figure A3.5 Patterson River rainfall and storm events (January – June 2010)..................49 Figure A3.6 IMOS shipborne track data (March 7 - 10 2010) ............................................50 Figure A3.7 Victorian temperature deciles (January – June 2010) ....................................51 Figure A3.8 Map of WQBMP exceedences (January – June 2010)...................................52 Figure A3.9 Two Bays continuous water quality monitoring measurements (10-23 January 2010)..................................................................................................................................54 Figure A3.10 Surface water temperature at Central Bay (January – June 2010)...............55 Figure A3.11 February surface water temperature across PPB and the Yarra River (2008 – 2010)..................................................................................................................................55 Figure A3.12 IMOS shipborne water temperature measurements for PPB (August 2008 – July 2009 and September 2009 – June 2010) ...................................................................56 Figure A3.13 Average salinity for PPB (January 2008 – June 2010).................................56 Figure A3.14 Hobsons Bay surface and bottom salinity measurements (December 2009 – June 2010).........................................................................................................................57 Figure A3.15 Yarra River at Newport CTD salinity profiles (January – June 2010) ...........57 Figure A3.16 Popes Eye CTD salinity profiles (January – June 2010) ..............................58 Figure A3.17 IMOS shipborne salinity measurements for PPB (August 2008 – July 2009 and September 2009 – June 2010) ...................................................................................58 Figure A3.18 Hobsons Bay surface salinity and chlorophyll-a