Derwent Catchment Review PART 1 Introduction and Background Prepared for Derwent Catchment Review Steering Committee June, 2011 By Ruth Eriksen, Lois Koehnken, Alistair Brooks and Daniel Ray Table of Contents 1 Introduction ..........................................................................................................................................1 1.1 Project Scope and Need....................................................................................................1 2 Physical setting......................................................................................................................................1 2.1 Catchment description......................................................................................................2 2.2 Geology and Geomorphology ...........................................................................................5 2.3 Rainfall and climate...........................................................................................................9 2.3.1 Current climate ............................................................................................................9 2.3.2 Future climate............................................................................................................10 2.4 Vegetation patterns ........................................................................................................12 2.5 River hydrology ...............................................................................................................12 2.5.1 Overview....................................................................................................................12 2.5.2 Long-term flow patterns in the Derwent...................................................................17 2.5.3 Diversions out of the Derwent...................................................................................21 2.5.4 Short-term flow variability in the Derwent ...............................................................22 3 Water allocations and use ..................................................................................................................26 3.1 Water usage....................................................................................................................26 3.2 Water licenses, allocations and surety levels .................................................................26 3.3 Water allocation by region..............................................................................................28 3.3.1 Lower Derwent River and Tributaries........................................................................28 Water Use Restrictions...........................................................................................................30 3.3.2 Upper Derwent River and Tributaries (Above Meadowbank Dam) ..........................33 3.3.3 Ouse River..................................................................................................................35 3.3.4 Clyde River .................................................................................................................39 3.3.5 Other Tributaries .......................................................................................................43 3.4 Hydro Storages................................................................................................................45 3.5 Irrigation schemes (future) .............................................................................................45 3.5.1 Shannon Clyde Irrigation Scheme..............................................................................45 3.5.2 South East Irrigation Scheme.....................................................................................47 3.5.3 Future irrigation expansion and sustainable yields ...................................................48 3.6 Drinking Water Supply ....................................................................................................48 Page i PART 1 Derwent Catchment Review 3.7 Non-consumptive water use...........................................................................................52 3.7.1 Hydro-electric power generation ..............................................................................52 3.7.2 Aquaculture and fisheries..........................................................................................52 4 Land uses and natural values..............................................................................................................53 4.1 Land Use..........................................................................................................................53 4.1.1 Industry and urban centres........................................................................................56 4.2 Natural values .................................................................................................................56 4.2.1 Wetlands....................................................................................................................56 4.2.2 Geoconservation........................................................................................................57 5 Water quality and quantity management ..........................................................................................60 5.1 Overview .........................................................................................................................60 5.2 Protected Environmental Values ....................................................................................60 5.3 Water quality guidelines.................................................................................................60 5.4 Water Management Plans ..............................................................................................64 5.5 Rivercare and Conservation Action Plans .......................................................................64 5.6 Hydro Tasmania management and issues ......................................................................64 6 Known inputs to the Derwent and identified water quality threats ..................................................66 6.1 Land Use driven inputs....................................................................................................66 6.2 Sewage Treatment Plants ...............................................................................................66 6.3 Level 2 activities..............................................................................................................67 6.4 Forestry ...........................................................................................................................67 6.5 Agriculture.......................................................................................................................67 6.6 Pesticides ........................................................................................................................69 6.7 Fish farms........................................................................................................................69 6.8 Threats to natural systems and conservation areas.......................................................70 6.9 Climate change................................................................................................................70 6.10 Salinity.........................................................................................................................70 6.11 Impacts of regulated flow regimes .............................................................................70 Page ii PART 1 Derwent Catchment Review Table of Figures Figure 1 Greater Derwent catchments .......................................................................................2 Figure 2 Map of the study areas showing major waterbodies, towns and rivers within the greater Derwent catchment. ......................................................................................................4 Figure 3 Broad geological features of mainland Tasmania, based on Seymour et al, 2006.......5 Figure 4 Geomorphic river types of the greater Derwent catchment........................................7 Figure 5 Location of karst systems within the greater Derwent catchment. ...........................8 Figure 6 Rainfall at Lake St Clair National Park, and at Bushy Park showing variability within catchment ...................................................................................................................................9 Figure 7 Average rainfall & runoff (mm) for the River Derwent, compared to major rivers in Tasmania...................................................................................................................................10 Figure 8 Projected rainfall variation for near future (2010 – 2030) under scenario A2 high emissions ..................................................................................................................................11 Figure 9 Schematic representation of power developments in the Derwent Catchment ......14 Figure 10 Schematic of Derwent catchment showing main flow paths and water storages in Hydro system. ...........................................................................................................................16 Figure 11. Monthly flow analysis for select waterways in the Derwent catchment based on average daily flow data. ..........................................................................................................17