1.1.4 Hydrogeology and groundwater quality

Summary

The Galilee subregion consists of seven groundwater systems. These include: the Cenozoic units, the north-eastern part of the Eromanga Basin, the Galilee Basin, Adavale Basin, Belyando Basin, the north-western part of the Drummond Basin, and the underlying Mount Isa Inlier and Thomson Orogen. The groundwater systems most relevant to the Galilee subregion are the Cenozoic, Eromanga and Galilee basins. Very limited hydrogeological information is available for the Adavale, Belyando and Drummond basins, the Thomson Orogen and the Mount Isa Inlier, and this was not included in this contextual report. These basins and geological basement may require assessment in subsequent project components if considered relevant to the impacts of coal seam gas (CSG) and coal mining development. There is also minimal existing information on the hydrogeology of the Cenozoic units and hydrogeology and hydrochemistry data for the Galilee Basin.

The main aquifers of the Galilee Basin are the Triassic Warang and Clematis groups, and the Late Permian Colinlea Sandstone. The Carboniferous Lake Galilee Sandstone is the only aquifer of the Permian – Carboniferous Joe Joe Group, which also consists of partial aquifers such as the Aramac Coal Measures and the Jochmus Formation. The main aquifers of the Eromanga Basin include the Cretaceous Winton, the Mackunda Formation, the Wyandra Sandstone member of the Cadna-owie Formation, the Jurassic – Cretaceous Hooray Sandstone, and the Jurassic Adori and Hutton sandstones. The Mueller Sandstone is the main Cenozoic aquifer of the Lake Eyre Drainage Basin and it occurs in the north-western part of the Galilee subregion.

Based on the Australian Drinking Water Guidelines (NHMRC and NRMMC , 2011), the water qualities of the Wyandra, Hooray and Hutton sandstone aquifers are mostly fresh to poor, with some brackish groundwater. Those of the Winton and Mackunda formations are dominantly brackish, with subordinate fresh water. Groundwater qualities in the Cenozoic aquifers are commonly fresh to poor, with some being brackish and saline. Groundwater quality in all the aquifers varies with depth to a certain extent and both fresh and saline groundwater can coexist in the same location at different depths. The distribution of groundwater quality is three dimensional, with potential compartmentalisation within some aquifers of the basins.

The hydraulic head gradients of the Eromanga Basin aquifers are high in the east and decrease towards the west. Albeit based on limited data, the hydraulic gradient of the Triassic Warang and Clematis group aquifers of the Galilee Basin appear to decrease from the south-east towards the centre of the subregion, which may suggest discharge as baseflow to the Carmichael and Belyando rivers. This will be further examined in subsequent project components.

There are 28 Water Resource Plans across Queensland of which seven are relevant to the Galilee subregion. Only three of these refer to groundwater in addition to surface water. The Water Resource Plans that encompass the Galilee subregion include those for the Burdekin Basin, Cooper Creek, Fitzroy river basin, Georgina and Diamantina, Bulloo and Nebine catchments, Gulf, and the Great Artesian Basin.

The Great Artesian Basin Water Resource Plan provides water reserves for aquifers in the Triassic sequences of the Galilee Basin, as wells as aquifers in the overlying Eromanga Basin. As there is not one management unit that considers the water reserves for the whole Galilee subregion, they must be inferred from seven plans that overlap the basin.