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The episodic, seasonal hydrology of Lake Eyre Basin (LEB) rivers produce a series of waterholes which provide critical aquatic refugia and essential water supply during predominantly dry periods. This study used direct measures of water loss, regional meteorological data, and waterhole bathymetry to develop calibrated waterhole persistence models in a range of waterhole types throughout the Queensland portion of the LEB. Evaporation was a major driver of waterhole persistence, whereas the influence of other water balance parameters (e.g. groundwater discharge, seepage, vegetation utilisation) varied between waterholes and years. Estimates of waterhole persistence were extrapolated to the regional scale using a modelled time-series of waterhole level data and Landsat satellite imagery (1988–2019). Strong relationships were calculated between waterhole level and waterhole area (r2 = 0.88) and waterhole level and number of waterholes (r2 = 0.79) for all regional waterhole zones. Using these relationships and predicted evaporation rates under three possible future greenhouse gas scenarios, modelling showed that, by 2070, the number of persistent waterholes could reduce by up to 67% over 12 month period without flow. Similarly, reductions in waterhole area of up to 72% are possible under drier climate scenarios. These results potentially represent a significant risk to the aquatic ecosystems and other waterhole-dependent users for an already limited resource. • Evaporation is a major driver of Lake Eyre Basin waterhole persistence. • Waterhole persistence is modelled at an individual waterhole and regional scale. • Predicted higher evaporation rates under future climate change scenarios highlights significant reductions in waterhole persistence. • Estimated reductions represent a risk to aquatic ecosystems and other waterhole-dependent users. • Results highlight the need for climate change adaptation and management strategies that support waterhole sustainability. [ABSTRACT FROM AUTHOR]

Hydrological connectivity between rivers and wetlands is considered one of the key critical factors for the integrity of floodplain landscapes. This study is a comprehensive modelling exercise on quantifying flood-induced wetland connectivity and the potential impacts of climate and water storage in an unregulated river basin in northern Australia. Flood inundation was simulated using a two-dimensional hydrodynamic model and the connectivities between wetlands and rivers were calculated using geoprocessing tools in ArcGIS. Wetlands in the floodplain were identified using waterbody maps derived from satellite imagery. A broadly representative sample of 20 wetlands were selected from 158 wetlands in the Mitchell basin considering location, size and spatial distribution. Five flood events ranging from 1 in 2 to 1 in 100 years were investigated to evaluate how connectivity changes with flood magnitude. Connectivities were assessed for the current condition as well as for two scenarios of future climate (Cwet and Cdry) and one scenario of dam storage. Results showed that a 1 in 100 years event inundated about 5450 km2 of land compared to 1160 km2 for a 1 in 2 years event. Average connectivity of wetlands in the Mitchell basin varies from 1 to 5 days for the floods of 1 in 2 to 1 in 26 years. As expected, a large flood produces longer duration of connectivity relative to a small flood. Results also showed that reduction in mean connectivity under a dryer climate (up to 1.8 days) is higher than the possibility of increase under a wet climate (up to 1 day). The impacts of a water storage, in the headwater catchment, are highly pronounced in terms of inundation and wetland connectivity (e.g., mean connectivity reduced by 1.7 days). The relative change in connectivity is higher for a small flood compared to that of a large event. These results demonstrate that there is a possibility of both increase and decease in connectivity under future climate. However, any water storage will negatively impact the connectivity between floodplain waterbodies and thus reduce the material exchange resulting in a reduction in primary and secondary productions in rivers and wetlands. [ABSTRACT FROM AUTHOR]