Introduction
Murray River is one of the Murray darling systems which flows in about 500km.it is located in South Australia. It passes through the lower Lakes and Coorong wetlands and drain to the sea. It covers about 300,000km2 of Southern Australia and it consists of sequence of Proterozoic to Mesozoic igneous and metasedimentary rocks Lawrence, 1975, 1988; Brown, 1989; Evans & Kellett, 1989). Murray River basin is about 600m thick.
Murray River is managed by the series of nested plants which is under the Natural Resources Management Act 2004 (NRM Act).the part of the River that is defined as prescribed water course is managed by Water Allocation Plans (Government Gazette Notice, 1978).
Murray River basin underlie low salinity is about TDS less than 5000mg/l ground water lens. Its lens is recharged through the riverbank with unlimited recharge from the flood plains. The lense recharge mostly occurs during the high river levels and low salinity water which forms base flows to various rivers when it reaches low river levels.
In 1990s to the mid 2000s Murray River lens shrunk during this time when there was drought. It will continue to shrink until a regular high flows is established in River Murray. The regional water table will rise due to land clearing which will increase the hydraulic radiant between the regional ground water and the lens ground water which can make it to degrade. When the low salinity ground water in the lens is replaced with saline ground water, it will automatically increase the salinity of the river while reducing the utility for the water supply which will impact to riverine ecosystems (Cartwright, Weaver, Simmons, Lawrence & Robert, 2009).
Impact if climate change on Murray River Basin
The world is going through a climate change and South Australia has not been left behind. Its climate is changing over the last century. South Australia has been experiencing high temperature, change in seasons and low rainfall which has impacted negatively on the stream flow (Department of Agriculture Forestry and Fisheries et al., 2008).this will result to reduction of water consumption across Murray darling basin by about 42 to 53 percent (Wentworth Group of Concerned Scientists, 2010).
The current development modeling for service water and 1997 to 2006 climate scenario discovered that the average annual rainfall and modeled runoff for the current climate in the Murray region which consists of Victoria and South Australia planning area. They were lower by 8 percent and 21 percent than in a long term average will fall to about 27 percent. The were predictions that the average service water availability in Murray region will decrease by 30 petcent, end of system flows at the Barrages would reduce by 50 percent . The total diversion would reduce by 13 percent (CSIRO, 2008),
Anthropogenic climate change is predicted to decrease the overall rainfall in South Australia (inter-governmental panel on climate change, 2007). This may continue reducing the drainage of Murray River basin. Even thogh the net river discharges are reduced, it is critical that during high environmental river flows are maintained or else this and other low salinity ground water lenses in the Murray dam basin will continuously shrink.
Geological and ecological features
Murray River basin consists of three sub-basins or provinces which include Riverline, Scotia & Mallee limestone which are separated by basement ridges
Murray river basin shows the depth of the basement and underground flow path. The MLP stands for Mallee Limestone Provision, RP stands for Riverin Provision, SP stands for Scotia Provision. The boundaries between the Riverin and Scotia/ Mallee Limestone provision which is indicated by dash line and the boundary that separates Scotia and Mallee is the Murray River (MR). NSW stands for New South Wales, SA stands for South Australia, Vic stands for Victoria (b) stratigraphic cross section between x and x1(a) indicates a major unit in murray basin (Evans & Kellett, 1989). Groundwater flow is deflected upwards by the Geera clay (Brown, 1989).
The groundwater flow on salinity map of the Mildura Swan hill region (Telfer et al., 2006) hydrolic head and ground water flow parts are located in Parilla Aands.
history of human settlement
The land around Murray River basin was claimed by United Kingdom in 1788 when the European settled in around these areas.
Settlement around Murray River basin was slow therefore, the railroad was introduced later to the river towns which had a major impact on the steamers along the Murray. In 1887, Irrigation was introduced Canada citizen known as George Chaffey around Mildura in Victoria and Renmark which is located in South Australia. This boosted the rate of settlement and exploitation of the Murray river’s water supply.
It is believed that from about thousands years Aboriginal people have been relying on the Murray river’s abundance. The Aborigines were hunter gatherers and they used a simple mechanism to attain their achievements. They attained a remarkably complex social Organization and spiritual beliefs and practice which were key tribal and territorial. Every individual had a strong association with their piece of country and their own language group. Though the hierarchical, Aboriginal society was very open and they did not have any established with the system of chiefs or any institutionalized political or social governance arrangements. They did not believe in national identity and lived a remarkable balance with what the nature provides.
Aboriginal society population started to decline between 1830 and 1860oMurra due to introduction of disease such as measles, influenza and smallpox and they did not have immunity for them. The other reason for their decline is the direct conflict which they had with Europeans. Rufus River Massacre which is near Lake Victoria in 1841 is most commonly known. Later on in 1850 during the gold rushes of the, Aboriginies replace European workers on many Murray stations and fenced the land.
Some researchers indicates that they have a higher number of population which is three quarters of a million by the time European settlement began. Aboriginal society are about 410,000 which is 2.2 percent of the total population.
Various groups settled along the land around the Murray River basin who include Ingalta, Moorundie, Goodwarra, Parrian kaperre, Tongwillum, and Yoorlooarra. The Ngarrindjeri people lived in the River land South Australia ,and the Coorong lived along the lands which surrounds the Murray and they are the largest Aboriginal community in South Australia. Irrigation and fishing is the major source of food to people living in areas around Murray River basin.
Climate change
There was a rapid extension of irrigation development in the MDB which was introduced between 1950s and 1980s. It did not consider change in climate. The observation was done during the wet period and it had an exemption of four years dry period. During wet, expansion period the mean and variance of annual rainfall raised (Khan, 2008) and they were relatively higher between 1900 and 1950.
Fig 4: annual rainfall anomaly, Murray Darling basin.
Murray River basin management Plan
Limit in water consumption
Water Resource plans is a crucial when it comes to management plan in Murray River basin. A new rule has been set on the amount of water that can be used from the system which will help to make sure that sustainable diversion limit is not exceeded in future.
Respond to climate change
Recent studies that has been conducted on projected climate change in Murray Darling basin shows that the future average temperature will increase while the rainfall will reduce which results to decrease in water flow in Murray River. The sea level in South Australia is predicted to rise by at least 30 centimetres by 2050 and 1 metre by 2100.
South Australia is considered to bea leader in capturing and recycling of stormwater and wastewater. They have desalination plant which can provide half of metropolitan Adelaide with a water supply that has been harvested during the rainy seasons.
Reserches and projects are launched in order to support the river’s irrigation industry to use water more efficiently and diversify into areas that use less water.
Implementing the Basin Plan will also help the River Murray adapt to a changing climate. Reducing the amount of water taken from the river and returning to a more natural cycle of wetting and drying will better prepare the river system to cope in dry times and reduce the impacts of extreme drought like the one happened thousands years ago.
The Basin Plan was startedin November 2012, when the Commonwealth reached an agreement with each of the Basin states which include Queensland, New South Wales, Victoria, South Australia and the Australian Capital Territory.
South Australia is working hard in making sure that the Basin Plan is implemented and meets its intended objectives. A significant progress has been made towards the implementation.
Basin Plan implementation progress
● Over 2000 gigalitres of water for the environment has been secured.
● More than 750 watering events since 2013 to 2014 that are delivering real environmental benefits across the Basin.
● Irrigated agriculture has been maintained at around $7 billion annually even with recovery of water for the environment
Conclusion
Murray River basin has been negatively affected by climate change in South Australia. It has resulted to reduction of water flow. It has been predicted that the change in climate will continue which can lead to dryness of Murray River if the implementation plan by South Australia government fails.
Decrease in rainfall and streamflow, and increase in temperature has affected the natural cycle of floods and droughts which change the hydrology of the Murray river basin system. This is a major risks which has a significant consequences for the environmental health of the Murray Darling Basin.
Changes in global and regional climate patterns are have an effect on the availability of water for both communities and the environment throughout the Murray Darling Basin
The government and the residence has a big role to play to make sure that the river water level is maintained. Water harvesting will play a big role in maintainace of water level.
Adaptive future changes needs to be embraced in order to responses to climate change which can be further developed through monitoring of, and investigations into, climate change impacts. These will be a long term strategy and the Short term plan can be the environmental watering priorities.
References
Brown, C.M., 1989. Structural and stratigraphic framework of groundwater occurrence and surface discharge in the Murray Basin, southeastern Australia.Bureau of Mineralogy Resources Journal of Australian Geology and Geophysics 11, 127–146.
Cartwright, I., Weaver, T.R., Fifield, L.K., 2006. Cl/Br ratios and environmental
isotopes as indicators of recharge variability and groundwater flow: an example
from the southeast Murray Basin, Australia. Chemical Geology 231, 38–56.
Cartwright, I., Weaver, T.R., Fulton, S., Nichol, C., Reid, M., Cheng, X., 2004.
Hydrogeochemical and isotopic constraints on the origins of dryland salinity,
Murray Basin, Victoria, Australia. Applied Geochemistry 19, 1233–1254.
Cartwright, I., Weaver, T.R., Stone, D., Reid, M., 2007. Constraining modern andhistorical recharge from bore hydrographs, 3H, 14C, and chloride concentrations:applications to dual-porosity aquifers in dryland salinity areas, Murray Basin,Australia. Journal of Hydrology 332, 69–92.
Cartwright, I., Weaver, T.R., Tweed, S.O., 2008. Integrating physical hydrogeology,hydrochemistry, and environmental isotopes to constrain regional groundwaterflow: Southern Riverine Province, Murray Basin, Australia. In: Carrillo, R.J.J.,Ortega, G.M.A. (Eds.), International Association of Hydrogeologists SpecialPublication 11, Groundwater Flow Understanding from Local to Regional Scale. Taylor and Francis, London, UK, pp. 105–134
Evans, W.R., Kellett, J.R., 1989. The hydrogeology of the Murray Basin, southeastern Australia. Bureau of Mineral Resources Journal of Australian Geology and Geophysics 11, 147–166.
Government of South Australia, 1978. River Murray Prescription – Government Gazette Notice, 10 August.
Government of South Australia, 2009. South Australian Murray Darling Basin Natural Resources Management Board Water Allocation Plan for the River Murray Prescribed Watercourse (as amended July 2009).
Lawrence, C.R., 1975. Geology, Hydrodynamics and Hydrochemistry of the Southern Murray Basin. Geological Survey of Victoria Memoir 30, Melbourne, Australia. 359p.
Lawrence, C.R., 1988. Murray Basin. In: Douglas, J.G., Ferguson, J.A. (Eds.), Geology of Victoria. Geological Society of Australia (Victoria Division), Melbourne, Australia, pp. 352–363.