water resource issues in the lower murray darling basin
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Water resource issues in the Lower Murray Darling Basin. Dr John Tibby Senior Lecturer Geographical and Environmental Studies [email protected]. Murray Darling Basin. Identified as key threatened system in global scale assessments. Kundzewicz et al . in IPCC (2007). Key questions. - PowerPoint PPT PresentationTRANSCRIPT
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Water resource issues in the Lower Murray Darling Basin
Dr John TibbySenior LecturerGeographical and Environmental [email protected]
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Murray Darling Basin
Kundzewicz et al. in IPCC (2007)
Identified as key threatened system in global scale assessments
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Key questions
Will a weir be built across the River Murray at Wellington?
Can it be justified in terms of the “natural” state of Lake Alexandrina
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A weir: why?
Construct across bottom of River Murray to raise/maintain water levels upstream
Karlene Maywald, Water Security Minister, recently said a 30% chance of being built (The Australian, 6th Aug)
Up from 10% last year
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Australia is becoming warmer…
Most of the last 20 years have been warmer than average…
Source: www.climatechangeinaustralia.gov.au
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And drier…
Source: www.climatechangeinaustralia.gov.au
Drying trend for last ~ 50 years
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Predicted to get worse…
50% chance of 5% rainfall decline Perhaps a 25% reduction in stream
flow
Source: www.climatechangeinaustralia.gov.au
% change
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Water balance in MDB: 2006 Average natural flow to the sea:
14,000 GL: Average irrigation extraction:
11,000 GL
source: Ladson (2008)source: Ladson (2008)
Open channel cotton irrigation near Open channel cotton irrigation near St George, southern QueenslandSt George, southern Queensland
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Water “users” in MDB in 2020
Canberra bushfire regrowth: 130 GL Revegetation: 550-700 GL/yr Climate change: 1100 GL Living Murray Initiative: 500 GL/year?
source: adpated from Lawrie and source: adpated from Lawrie and Williams (2004)Williams (2004)
Revegetation near Myponga Revegetation near Myponga Reservoir, southern FleurieuReservoir, southern Fleurieu
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Sth Australian use of Murray
Have a “guaranteed” allocation of 1850 GL 570 GL: irrigation 170 GL: domestic water
(mainly Adelaide) 1110 GL: environment
Total storage Total storage volume in Basin: volume in Basin: 2300 GL2300 GL
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Adelaide water balance 2003 water use: ~280 GL Groundwater (bores): 6% Rainwater tanks: <1% Desalination plant: 50-80 GL/year average: 60% from Adelaide Hills
catchments, 10% in drought years
Mannum: Adelaide Mannum: Adelaide water offtakewater offtake
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Water level is going below offtakes…
Water level at Morgan (m above sea level)
2
4
6
8
10
Jul-74
Jul-77
Jul-80
Jul-83
Jul-86
Jul-89
Jul-92
Jul-95
Jul-98
Jul-01
Jul-04
Jul-07
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So…
Will a weir at Wellington be constructed? My money is on “yes”
Can it be justified in terms of the environment?
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Lake Alexandrina: naturally estuarine? Many claim Lake Alex would have
had regular marine incursions Don’t have a time machine… Not quite…
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The answer is in the mud…
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Lake Alexandrina diatoms
Modified, with permission from Fluin et al. 2007, Hydrobiologia 591
Little marine incursion Little marine incursion in 7000 yrsin 7000 yrs
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In conclusion
Can’t justify letting in marine water in terms of naturalness
However can prevent other environmental problems
Now your questions…
Swanport wetland, Swanport wetland, Murray BridgeMurray Bridge
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References
Fluin, J., Gell, P., Haynes, D., Tibby, J. and Hancock, G. 2007. Palaeolimnological evidence for the independent evolution of neighbouring terminal lakes, the Murray Darling Basin, Australia. Hydrobiologia 591(1): 117-134.
Ladson, A. 2008. Hydrology-An Australian Introduction. South Melbourne, Oxford University Press.
Lawrie, K. and Williams, M.A.J. 2004. Improving salinity hazard predictions by factoring in a range of human impacts in the context of climate change. In: I.C.Roach (ed.) Regolith 2004: Proceedings of the CRC LEME Regional Regolith Symposia, 199-203. Cooperative Research Centre for Landscape Environments and Mineral Exploration
Climate change in Australia: http://www.climatechangeinaustralia.gov.au/
The Intergovernmental Panel on Climate Change, 4th Assessment Report: http://www.ipcc.ch/