The Ecological Elements Method for adjusting the Murray–Darling Basin Plan Sustainable Diversion Limit: Overview of method development and evaluation

[摘要] The Murray–Darling Basin is one of Australia’s premier environmental assets, and is a vital resource for Australian agriculture, industry and local communities. The Australian federal and Basin state governments are committed to the Murray–Darling Basin Plan to protect this asset and ensure it is managed sustainably.Adjusting sustainable diversion limitsThe Basin Plan (MDBA, 2012) aims to achieve a healthy, sustainable, working Basin by balancing environmental, economic and social considerations. A key component of the plan is ‘sustainable diversion limits’ (SDLs). These are the maximum amount of surface and groundwater that can be taken from the Basin for agricultural and human consumptive use. The Murray–Darling Basin Authority (MDBA) estimated that the environmentally sustainable level of take is 10,873 gigalitres per year (GL/y), averaged over the long term. This has been set as the current SDL. This is, on average, 2,750 GL/y less than what was used in the Basin in June 2009.The Basin Plan allows SDLs to be increased or decreased (within limits) as long as environmental, social and economic outcomes are maintained or improved. SDLs can be increased if changes to infrastructure or water management or river operating practices enable the same environmental outcomes to be achieved with less water. The plan includes details of an ‘environmental equivalence test’ which the MDBA will use to assess whether environmental outcomes are maintained if the SDL is increased. CSIRO has developed a method to test the environmental equivalence of potential SDL adjustments — the Ecological Elements Method. The Ecological Elements Method compares environmental outcomes at the regional scale for benchmark and SDL-adjusted scenarios. The test requires the region environmental outcome score for the SDL-adjusted scenario to be equivalent or higher than the score for the benchmark scenario. The region is the southern connected Basin of the Murray-Darling Basin.Developing and using the Ecological Elements MethodA CSIRO-led team has developed the Ecological Elements Method over two years. The method uses 12 elements from three ecological classes: vegetation, waterbirds and fish. It takes into account the life cycles, breeding and recruitment requirements to define stress and recovery times for each ecological element (expressed as preference curves). The development of the method involved developing the preference curves and rules which relate ecological response to changes in flow, metrics for weighting environmental significance and rules for combining scores to provide an aggregate environmental outcome score at the region scale. The method was based on published literature sources and the expert knowledge of scientists and consultants engaged as part of the CSIRO-led team. It also took account of input from an independent review panel, Basin governments, and the MDBA. The method is consistent with requirements of the Basin Plan (Chapter 7 and Schedule 6), including that the method be independently reviewed. An independent panel of scientists have reviewed the method at key stages throughout the method development and subsequent trial (Jones et al. 2014; Jones et al. 2015). (See also Development of the Murray–Darling Basin Plan SDL Adjustment Ecological Elements Method, CSIRO, 2014)Trialling and reviewing the Ecological Elements MethodFollowing an initial testing phase on two reaches in the River Murray, the MDBA trialled the method over all reaches in the southern connected region. The CSIRO-led team designed a program to test the trial results, reviewed the trial implementation for consistency and fidelity with the Ecological Elements Method, and assessed whether ecological outcome scores are ‘ecologically meaningful’ at local and regional scales (i.e. scientifically justifiable and fit-for-purpose). CSIRO also examined scaling and sensitivity issues.

[发布日期] 2015-07-27 [发布机构] CSIRO

[学科分类] 地球科学(综合)