Long-term persistence and connectivity of in-channel refuge waterbodies in the Darling (Baaka) River

Long-term persistence and connectivity of in-channel refuge waterbodies in the Darling (Baaka) River

Journal article: Persistence and connectivity of in-channel waterholes in the Darling (Baaka) River – An analysis using satellite imagery and graph theory 

• In-channel persistent surface water provides critical refuge habitat for aquatic organisms in the Murray–Darling Basin. Refuge habitats ensure the survival of aquatic organisms during low and cease to flow conditions, which have increased in frequency and duration since pre-development in the Basin.
• This project provides scenario evaluations for the presence and connectivity of aquatic habitat under different flow regimes (e.g., under climate change and water use).
• This document outlines the methods, results and discussion on GIS, graph theory and model use and performance, response to climate change, and management implications.

• Connectivity of persistent aquatic habitat varied throughout the river: upper segments showed seasonal changes, middle segments had both stable and fluctuating habitats, and lower segments were more consistent in water coverage. The central region contained important habitats acting as hubs for ecological activity. Connectivity was influenced by the distance between habitats, with more isolated areas being less connected.
• Weirs impacted the persistence and connectivity of the Darling (Baaka) River. Weir pools provided areas of persistent water upstream of the weirs. However, downstream of the weirs there were long stretches of river containing few, isolated persistent aquatic habitats that were more often disconnected than connected, presenting a significant dispersal challenge for fish.
• Flow levels were the most significant predictor of connectivity, with climate trends and rainfall also influencing connectivity. Future climate models suggested that wetter conditions would slightly increase connectivity, whereas drier conditions would reduce it.
• Using logistic regression, the study predicted the connectivity of nine selected water bodies, showing that higher flows are needed to connect isolated habitats.
• These models help in river management by forecasting connectivity under different scenarios and can be updated with new data or applied at different scales (e.g. whole basin). The study emphasises the ecological importance of these habitats in the Darling (Baaka) River and the need for effective flow management to sustain them.