The volumetric value for the line item is 53 ML. Regional groundwater flow across the Murray–Darling Basin (MDB) region boundary is only considered important in aquifers underlying the MDB surface drainage outlet to the Southern Ocean. The boundary through which groundwater flow is estimated is highlighted in the figure included in Quantification approaches for Line Item 15.1.1, but only for sections of the MDB boundary that are not co-incident with the coastline.
Bore locations and groundwater level data in South Australia were sourced from the Water Regulations 2008 (category 2A) information returns provided by Department for Water South Australia (Provider Code W0078) to the Bureau of Meteorology.
The geographic information system (GIS) data relating to the boundaries of the aquifers and Groundwater Management Units (GMUs) were extracted from the Interim Groundwater Geodatabase developed for the Bureau of Meteorology by Sinclair Knight Merz (SKM 2010a).
Bureau of Meteorology.
Regional groundwater flow across the MDB regional boundary is only considered important in aquifers underlying the MDB surface drainage outlet to the Southern Ocean. The boundary through which groundwater flow is estimated is highlighted in the figure included in Quantification approaches for Line Item 15.1.1. Groundwater flow was estimated for the Murray Group Limestone and the Renmark Group Aquifers where the identified boundary is not co-incident with the coastline.
Groundwater flow was calculated using a simple GIS approach based on Darcy’s Law. Groundwater levels were interpolated for seasons using the ArcGIS Topo-to-Raster tool from reduced groundwater levels measured at monitoring bores. Seasonal groundwater flow-grids were derived from groundwater level grids, aquifer thickness and hydraulic conductivity using a modification of the ArcGIS Darcy Velocity tool. Groundwater flow across selected flow boundaries (see the figure included in Quantification approaches for Line Item 15.1.1) was then calculated using a simple GIS analysis and seasonal values were aggregated to the 2009–10 reporting period.
The uncertainty is ungraded.
The uncertainty in the field-measured data (e.g. groundwater levels, hydraulic conductivity) were not specified and unknown, and hence the impacts of such uncertainty on the calculated groundwater flow is not estimated.
The regional flow estimations were based on the interpolated groundwater level grids produced using ArcGIS Topo-to-Raster tool. Use of different interpolation methods may impact on the values of the groundwater level grids and hence the estimated regional flow.
Groundwater flow was estimated for a simplified boundary constructed from a series of line segments. Groundwater flow across this boundary was calculated using the method described above. The uncertainty surrounding this simplification was not analysed.