Multiple lines of evidence provide a holistic and testable conceptualisation of complex ecosystem-groundwater dynamics at the Doongmabulla Springs Complex, Queensland, Australia

The Doongmabulla Springs Complex (DSC) in Central Queensland, Australia, consists of over 160 individual springs ranging from vents less than 10 cm across supporting individual tussocks of grass to wetlands over 9 hectares with permanent pools of water. These unique springs are home to a variety of plant species (many endemic) that are specially adapted to the varied physical, chemical and hydraulic conditions of the local environment and the groundwater discharge on which they rely.

We have examined these springs across multiple spatial and temporal scales, using remote and field data acquisition techniques, to develop a detailed understanding of the water, soil and floristic characteristics and dynamics at a selection of these springs, quantifying spring extents and changes over time as well as documenting species zonation and vegetation dynamics related to seasonal and climatic variability and the local physico-chemical conditions. From these targeted studies we can interpolate and extrapolate to the other springs in the complex and identify where additional studies may be required to fill data gaps.

Critically, local multi-spectral and thermal drone imagery has augmented regional satellite imagery to constrain spatial discharge patterns of springs and provides spatial linkages that complement visual images taken at the same time. On-ground surveys have identified new springs in some areas and loss of others and can be linked to regolith variability and sub-surface source aquifer pressure controls. The thermal imagery provides a platform to observe and quantify spring discharge changes season to season. Spot sampling of surface waters and groundwater highlights inter-seasonal variability in water source chemistry, whilst isotopes highlight the changing importance of groundwater for maintenance of groundwater discharge and consequent support of spring health. Notably, water samples taken for chemical and isotopic analysis included run-of-river Radon-222 analysis that helps highlight the groundwater discharge constrains.

Underpinning the local-scale observations, regional groundwater pressures define the dynamics of the source waters, though spatially disparate bore data must be complemented by modelling interpolations. The multi-dimensional conceptualisation thus informs, and is informed by, a regional numerical groundwater model and links the regional observations with local-scale, spring-specific eco-hydrological modelling, which is described in a companion paper (Gibson, et al. these proceedings).  

The DSC conceptualisation must be coherent at all spatial and temporal scales and then it can be used to customise mitigation responses at individual springs based on groundwater impact modelling considering potential changes from climate change and local mining activities.