The Australian Government's Geological and Bioregional Assessment (GBA) Program is assessing potential impacts of shale and tight gas development on water resources and the environment in three onshore basins: Cooper, Isa and Beetaloo. The Isa GBA region is host to two major groundwater systems: a deeper Proterozoic system and a shallower system associated with sediments of the Carpentaria and Karumba basins, collectively part of the Great Artesian Basin. If shale gas were to be developed in the future there could be potential to impact groundwater and surface water and the ecosystems that rely on these resources.
Surface water – groundwater interactions are a key component of the hydrological system, important for supporting a variety of environmental assets. Analysis of earth observation data in this remote region has helped assess the interactions between surface water and groundwater where the availability of other spatial and temporal datasets is limited. In particular, new remote sensing methods have enabled rapid and consistent mapping of parts of the landscape with potential dependence on groundwater.
Two remote sensing products (Water Observations from Space summary statistics and Tasselled Cap Index wetness exceedance) were used to investigate the persistence of surface water and soil moisture in the landscape. In this region, areas that retain water for at least 80% of the time or are wet during the dry season (May to October) are likely to have a reliable groundwater source or access to groundwater during periods of limited rainfall. These areas most likely support groundwater dependent ecosystems, including springs.
Preliminary analysis of earth observation data has enhanced understanding of surface water – groundwater interactions in the Isa GBA region, complementing analysis of sparse streamflow, groundwater and hydrochemistry data. Targeted field validation could improve understanding of groundwater dependence in the landscape and enhance confidence in the findings of this assessment.