The Murray Darling Basin Plan and the Basin-wide environmental watering strategy define a series of outcomes sought by the Plan through the return of flows from consumptive users (often termed environmental water) into the river systems. Non-flow based interventions, such as infrastructure works to provide fish passage and/or mitigate downstream effects of cold water releases from storages, in-stream snagging to provide fish habitat, restoration of riparian vegetation and removing barriers to floodplain connectivity, have been proposed as contributing to achieving the overall environmental outcomes and have been termed ‘complementary measures’. These interventions do not replace flow-based measures – however, they are recognised as being important to the achievement of environmental outcomes. Indeed, there are certain to be benefits provided by Complementary Measures that will not be achieved through flow-based measures, hence the term ‘complementary’. Despite this, to date there has been no agreed method to assess the important contribution complementary measures make to the delivery of the outcomes of the Basin Plan. The Murray-Darling Basin Authority requested CSIRO to lead the development of a method, underpinned by an evidence-based conceptual framework, for assessing the relative environmental benefits (and dis-benefits) of complementary measures in supporting the achievement of the Basin Plan’s environmental objectives.
CSIRO and the MDBA worked in partnership with an eminent group of freshwater ecologists to scope and develop a preliminary method to assess the relative environmental benefits of Complementary Measures in the MDB. Environmental benefit criteria were defined for the Basin-wide environmental watering strategy’s four key themes of: (1) native fish; (2) waterbirds; (3) native vegetation and (4) river flows and connectivity. The project used a preliminary list of Complementary Measures proposed by jurisdictions, but the method we developed is adaptable and can be applied to any complementary measure in the future. The method consists of three components (called modules): (1) a potential benefit assessment module, (2) a (biological) functional groups assessment module that utilises conceptual models, probability models and expert elicitation; and a (3) cumulative relative benefit assessment module. Although there is more work to do, our method lays the foundation for an accepted approach to capture the important contribution Complementary Measures make to achieving the environmental outcomes of the Basin Plan.
Capability is drawn from freshwater ecologists, hydrologists, decision scientists, informatics specialists and quantitative ecologists. Resourcing from five Universities (Charles Sturt University, Deakin University, Latrobe University, The University of Melbourne, and UNSW) and three private contractors were used to complement skills within the project team.
Using existing knowledge, ecological and hydrological information was used to develop a flexible method capable of measuring the environmental benefit of complementary measures at different scales and in different contexts, laying the foundation for future research.
Investment by governments in Complementary Measures should be founded on a scientifically robust conceptual basis that synthesises our understanding of how non-flow related measures could contribute to achievement of Basin Plan objectives in combination with environmental water in a complex ecological system with competing resource needs. The project provideds a practical framework for use by policy makers through providing information on which Complementary Measures have greatest prospect of enhancing environmental benefits and identifying where benefits can be best achieved in addition to those possible with environmental water