The Murray-Darling Basin is the ‘food basket’ of Australia generating about $15 billion/year in agricultural production, a third of which is produced by irrigation. Irrigation (including conveyance) uses about 11,000 GL/year, representing 90% of the surface water consumed. On average these extractions reduce annual flows in the lower Murray by about 60%, and in dry periods flows are reduced by up to 96%.
This level of water use has contributed to wide ranging decline in the aquatic ecosystems of the basin. Evidence of this degradation led to the capping of surface water extractions in the mid-1990s. This was followed by the 2004 National Water Initiative and the Water Act 2007 (Cth) in which governments agreed to ‘…complete the return of all currently over-allocated or overused systems to environmentally sustainable levels of extraction’. The imperative for change was heightened by the Millennium drought which contributed further to environmental decline and involved previously unforeseen water scarcity for many consumptive users.
The Water Act 2007 established the Murray-Darling Basin Authority and tasked the Authority with preparing a Basin Plan to set sustainable diversion limits. The Basin Plan is likely to recommend significant reductions in extractions. Any reductions will involve socio-economic impact while a failure to significantly reduce extractions may result in further environmental decline.
A robust understanding of the relationships between water resource use, ecology and socio-economic impact is important in making the key policy decisions and communicating the basis of these decisions to stakeholders. Over many years Government and research institutions have developed an array of models that can assist. These include:
The application of these models to support whole-of-Basin policy is challenging due to the different spatial/temporal timescales, baselines and extension of the models beyond the purpose for which they were developed.
Questions
What models can, and have been used, to reconcile the competing claims over how much water should be allocated for environmental flows and how much for irrigation purposes?
What might be impeding accurate data collection and the development of models (ecosystem, hydrological, socio-economic) and their acceptance by decision-makers?
What systems/technologies/innovations could be developed to better model the consequences of policy decisions in the Murray Darling basin (eg the response of different vegetation types and fauna species to variable flow regimes)?
What additional resources or capabilities are required to achieve this?
What modelling and research, in addition to ecosystem models, may be required to inform the debate about water reform and to assist decision makers in their policy development for the Basin?
How important is a notional ‘baseline’ or pre-European system state for our management decisions, and can we determine that state?
What are some of the major uncertainties that must be considered in using models to inform policy?
How could models of this ecosystem be applied more broadly to other ecosystems (such as the other three breakout group scenarios)?
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