The volumetric value for the line item is 2,117 ML. Groundwater discharge to the sea can only occur across the Murray–Darling Basin (MDB) boundary in the area near the mouth of the Murray River in South Australia. This flow was estimated for the highlighted boundary shown in the figure included in Quantification approaches for Line item 15.1.1 but only where the identified boundary is 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 of 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.
Groundwater discharge into sea across the MDB regional boundary is only considered to be significant in the area near the mouth of the Murray River in South Australia. 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 where the identified boundary is co-incident with the coastline. Groundwater discharge into sea was estimated for the Murray Group Limestone Aquifer and Renmark Group Aquifer.
Groundwater discharge into sea 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.
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.
National Water Account 2010
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