Corangamite CMA Anglesea River Estuary Flow Assessment Final Approved Report January 2016 Table of contents Executive Summary ................................................................................................................................. v 1. Introduction..................................................................................................................................... 1 1.1 Anglesea River estuary ........................................................................................................ 1 1.2 Purpose of this report........................................................................................................... 3 1.3 Scope and limitations ........................................................................................................... 4 Part 1: Physical, ecological and social changes to the Anglesea River estuary ...................................... 5 2. Predicted physical changes to Anglesea River estuary ................................................................. 5 2.1 Objective .............................................................................................................................. 5 2.2 Approach .............................................................................................................................. 5 2.3 Review of Relevant Literature and Data .............................................................................. 6 2.4 Conceptual Models and Modelling Framework ................................................................. 12 2.5 Multi-Annual Water Balance Model ................................................................................... 16 2.6 June 2012 Winter Hydrodynamic Modelling ...................................................................... 20 2.7 Geochemical Modelling - Winter 2012 ............................................................................... 23 2.8 Marshy Creek Observations .............................................................................................. 26 2.9 Summary of predicted physical changes ........................................................................... 28 3. Predicted ecological changes ...................................................................................................... 29 3.1 Objective ............................................................................................................................ 29 3.2 Approach ............................................................................................................................ 29 3.3 Floodplain and aquatic vegetation communities ................................................................ 29 3.4 Floodplain Fauna ............................................................................................................... 33 3.5 Aquatic ecology .................................................................................................................. 36 4. Social (and Economic) Impacts ................................................................................................... 42 4.1 Objective ............................................................................................................................ 42 4.2 Approach ............................................................................................................................ 42 4.3 Summary of impacts to social and economic value ........................................................... 46 5. Key Findings Part 1 ...................................................................................................................... 47 5.1 Summary of predicted physical changes ........................................................................... 47 5.2 Summary of predicted ecological changes ........................................................................ 47 Part 2: Assessment of options to manage changes to the Anglesea River estuary .............................. 49 6. Options Assessment .................................................................................................................... 49 6.1 Objectives .......................................................................................................................... 49 6.2 Approach ............................................................................................................................ 49 6.3 Summary of options assessment ....................................................................................... 54 6.4 Key Findings Options Assessment .................................................................................... 57 7. Conclusions .................................................................................................................................. 58 8. References ................................................................................................................................... 61 GHD | Report for Corangamite CMA - Anglesea River Estuary Flow Assessment 31/33459 | i Table index Table 1 Sum of major water balance terms over the water balance model application period (volumes in m3) ....................................................................................................... 17 Table 2 Geochemical concentration inputs for geochemical modelling. Colour coding re data sources is outlined in Table 3 .................................................................................... 23 Table 3 Colour legend for description of data source ..................................................................... 24 Table 4 Mixing ratio inputs for geochemical modelling ................................................................... 24 Table 5 PHREEQC geochemical modelling results ........................................................................ 25 Table 6 Anglesea Estuary: Ecological Vegetation Classes and their relative estuarine water dependency .............................................................................................................. 30 Table 7 Anglesea Estuary: Estuarine Dependant EVC’s and Habitats .......................................... 31 Table 8 Summary of current (status quo) estuarine conditions influencing vegetation communities ....................................................................................................................... 31 Table 9 Summary of changes to vegetation communities should groundwater pumping cease.................................................................................................................................. 32 Table 10 Summary of likely changes to terrestrial fauna resulting from mine and power station discharge (status quo) to in the Anglesea River estuary ....................................... 34 Table 11 Summary of likely changes to terrestrial fauna of changing mine and power station discharge to the Anglesea River estuary ............................................................... 35 Table 12 Summary of expected response of aquatic organisms in the Anglesea River estuary to the increase in summer flows and water height following the commencement of the mine and power station discharge ................................................ 39 Table 13 Summary of the expected response of aquatic organisms to the removal of the mine and power station discharge to the Anglesea River estuary .................................... 40 Table 14 Social and economic values impacted by physical and ecological changes resulting from reduced water levels and ecological changes as a result of ceasing the mine and power station discharge ................................................................. 44 Table 15 Feasibility impact and benefit screening process .............................................................. 50 Table 16 Summary assessment of mitigation opportunities to reduce the impact of changes to water levels and water quality as a result of ceasing the mine and power station discharge. The assessment defines the relative benefit of each mitigation option to key values ........................................................................................... 52 Table 17 Relation between estuarine levels, volumes and areas .................................................... 64 Table 18 Monthly evaporation estimates for Anglesea from BoM. ................................................... 64 ii | GHD | Report for Corangamite CMA - Anglesea River Estuary Flow Assessment 31/33459 Figure index Figure 1 View of Anglesea catchment highlighting major tributaries, mine and power station’s operations and the Anglesea River estuary .......................................................... 2 Figure 2 Mid-estuary pH of surface waters (source mine and power station from Pope (2006) in Maher (2011)). ...................................................................................................... 6 Figure 3 Inflow pH from June 2010 to May 2011 (from Maher (2011)). ............................................ 7 Figure 4 Rainfall and pH of Salt Creek, Marshy Creek and Anglesea River estuary at mine monitring site from November 2010 to January 2011 (Parsons 2011). ...................... 7 Figure 5 Salt Creek discharge and Al concentrations (data from mine and power station and Barwon Water in Pope (2010)). .................................................................................... 8 Figure 6 Temperature and salinity for top and bottom waters at Coogarah Park site (Pope 2006).