Water allocation to River Murray wetlands: a basin-wide modeling approach

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The primary aim of this project was to relate the water regime preferences of wetland plants to hydrology throughout the Murray River Basin and to predict the volume of additional water required to achieve optimal plant species diversity.

This report details the methods and key findings of the project which examined the impact of regulation and changes in water allocation on the community composition of wetland plants through the Murray River basin. Due to a lack of primary data, it deals only with a subset of wetlands. The study includes 2,746 wetlands with a total area of 53,303 hectares, spanning 16 hydrologically distinct reaches (Table 1). Geographically, these wetlands are restricted to areas of NSW and Victoria because no commence to fill (CTF) (sill height) data were available for wetlands in South Australia. This subset is approximately one-third of the wetlands spread through the NSW-Victorian portion of the river. A statistical modeling approach was used to analyse the relationship between discharge, CTF, wetland connectivity and the probability of occurrence of wetland plant species. This approached enabled a basin wide analysis. A key assumption was that the amount of water required for wetlands is that which optimizes plant species diversity at the regional spatial scale (here the 16 defined reaches).