10.3 Recharge from landscape
a. Groundwater model
The Department of Land Resource Management use the Finite Element Subsurface Flow system (FEFLOW) to estimate the natural water movement to and from the groundwater store within the Daly region.
FEFLOW estimates groundwater movement for the entire extent of the Oolloo aquifer and the Tindall aquifer, which extends beyond the Daly region boundary as shown in the figure below. The volumes reported in this account refer to the natural water movement that occurs within these aquifers within the Daly region boundary.
Map of the groundwater model area relative to the Daly region boundary
The Oolloo and Tindall aquifers are karstic and were modelled as an equivalent porous media with relatively limited storage. The groundwater model was calibrated using regional aquifer parameters to reproduce the observed groundwater levels and discharge to the rivers, as outlined in Knapton et al. (2010).
b. Supporting information
The volume recognised in the water accounting statements (2,970,000 ML) represents the volume of diffuse recharge to groundwater stores within the Daly region from the landscape during the 2011–12 year.
FEFLOW groundwater model.
Department of Land Resource Management.
Diffuse recharge from the landscape into aquifers within the region was estimated using the FEFLOW. Recharge into the aquifers occurs via the following pathways:
- direct recharge of excess soil moisture;
- precipitation 'channelled' through the unsaturated zone via macropores; and
- localised indirect recharge of surface water that is channelled into karstic features such as dolines (sinkholes).
Detailed information on the model calibrations are provided in Knapton et al. (2010).
Assumptions, limitations, caveats and approximations
It has been found that this methodology has not quantified the increase in recharge during wetter periods in the rainfall record when compared to groundwater level hydrographs and gauged flows.
The uncertainty estimate was not quantified.