River Murray ecological connectivity

The operation of multiple infrastructure assets and environmental flow delivery in the lower River Murray will alter riverine and floodplain hydraulics, and subsequently, the transport of resources, propagules (e.g. eggs, seeds) and biota from the floodplain to the river channel and along the river channel – processes that are critical for maintaining water quality and viable biotic populations in riverine-floodplain ecosystems. These processes may be expressed in altered ecological patterns, including changes to the occurrence of cyanobacterial blooms, hypoxic blackwater events and the recruitment of floodplain vegetation and large-bodied fish. Although the dependence of key ecological processes on inundation and hydraulics is known, there is limited specific knowledge available to describe the likely response to specific management scenarios.

This project adopted an empirical approach (with field, laboratory and modelling components) to investigate how inundation and hydraulic conditions alter the transport and transformation of resources (carbon and nutrients), propagules (e.g. eggs, seeds, larvae) and biota within and between the River Murray Floodplain and Channel and along the River Murray Channel. This has previously been identified as a key research need in the lower River Murray (see Goyder Project E.1.7 “River Murray Research Requirements”, Bice et al., 2014) and internationally (see “Challenges and Opportunities in the Hydrologic Sciences”, National Academy of Sciences, 2012).

The project utilised spatial and temporal gradients in hydraulic conditions in the Lower Murray to establish target conditions to facilitate the transport of resources, propagules and movement of biota between and through the river channel and floodplain. This included the use of managed inundation events only as there were no high flow events during the project timeframe. Various management scenarios were explored using hydrological and hydraulic models incorporating the available management levers. The model outputs were compared to the target conditions to describe the likely ecological response to the various management scenarios.