Arrow Energy has undertaken field investigations at four locations in the Surat Basin to understand if terrestrial ecosystems, identified through a desktop risk assessment, are dependent on the presence of groundwater.
The field investigations encompassed numerous complementary methods to derive multiple lines of evidence as to whether the ecosystems are groundwater dependent. The methods included coring to observe tree rooting depth, and assess hydrogeological conditions, assessment of soil moisture and leaf water potential, and stable isotope analysis of soil moisture, groundwater and xylem water.
Consequently, it was possible to identify, with a strong degree of confidence, the source zone of predominant moisture uptake and therefore hypothesise whether vegetation at each site was likely to fit the definition of a GDE.
This study provided multiple lines of evidence that up to three of the four locations are unlikely to fit the classical definition of a GDE and be reliant on groundwater from the regional water table aquifer, but rather are utilising shallow sources of soil moisture located above the regional water table aquifer, and that rooting depths of targeted tree species in the study areas are shallower than commonly thought.
The study’s outcomes have resulted in a more robust understanding of vegetation moisture uptake sources which in turn provides the basis for the revision of historical simplistic conceptual models of terrestrial GDEs in the Surat Basin and to provide direct evidence of the ability of targeted tree species to source water from the most accessible point within the ecosystem which is not always the regional water table aquifer.