Following closure of the Ranger Uranium Mine in 2026, the rehabilitated site will be a source of both contaminated surface water runoff and exfiltrating groundwater with elevated magnesium sulfate (MgSO4), derived from the leaching of waste rock capping. The sandy creek beds of Magela Creek adjacent to the mine have a relatively high hydraulic conductivity and will be a pathway for the transport of contaminants, including MgSO4, from the site. Little is known of the groundwater ecology of Magela Creek, nor of the potential impacts of this contaminant on these communities.
The aims of this study are to: 1) Characterise the shallow groundwater communities, and associated habitat and water quality, in Magela Creek; 2) Assess the sensitivity of these communities to contaminants arising from Ranger minesite; and, 3) Investigate the implications of elevated contaminants for ecological functions of these communities.
Initial results for this study observed elevated concentrations of Mg and SO4 in subsurface sands downstream of the mine compared to upstream values. During the dry season, after all surface waters dried or receded to small isolated pools, a resident fauna was observed in the dry and moist surface sands of Magela Creek. Invertebrates in the top 0.20 to 1.5 m of the sands were a mix of taxa commonly observed in surface waters, terrestrial taxa (soil fauna), and stygofauna (primarily harpacticoid copepods and syncarids).
Stygofauna are considered particularly sensitive to disturbance because they are adapted to near steady-state environment conditions and have narrow spatial distributions. Changes to environmental conditions, such as those predicted to occur in Magela Creek sand channel after closure, place stygofauna at potential risk.
The initial findings of the project will be presented, together with an outline of the proposed direction and design of this PhD study.