Understanding the contribution of groundwater to total evapotranspiration (ET) is critical for effective water resource management, particularly in groundwater-dependent ecosystems. This study focuses on partitioning total plant ET to quantify the proportion derived from groundwater sources. We applied a validated groundwater partitioning model—originally developed using a unique dataset from plantation forests in Mount Gambier—to floodplain environments. The model integrates field-scale soil moisture measurements taken at 2–4 week intervals throughout the soil profile down to the water table, enabling accurate estimation of groundwater uptake by vegetation. Model outputs were validated against observed groundwater fluctuations and demonstrated high reliability in representing groundwater extraction dynamics.
We applied this model to two pilot floodplain regions, Bookpurnong and Mallee Cliffs, where long-term groundwater depth data are available. These data support an additional validation method through comparison of modelled groundwater extraction with observed fluctuations. By combining remote sensing-derived actual ET (AET) and climate inputs, the model produces spatially explicit estimates of groundwater-sourced ET at the pixel level.
This approach advances a scalable method for identifying groundwater-dependent ecosystems (GDEs) and their water requirements across large floodplain areas. It provides a critical tool for assessing ecological risks, such as salinity impacts, and informing sustainable groundwater management. Deliverables include model validation in plantation settings and implementation for floodplain pilots, setting the stage for broader regional application.