Water resources data for Christmas Island were assembled as part of ongoing groundwater investigations and monitoring undertaken on Christmas Island during the period from October 1996 to June 1999.

The shapefile ‘vh_vulnerability.shp’ contains polygon data indicating the approximate area of the perched aquifer that is at very high risk from water contamination and over extraction.

Accuracy: The estimated extent of the boundary is based on information from salinity monitoring boreholes and some estimation based on knowledge of freshwater aquifer behavior on the island. The boundaries are somewhat subjective and are in fact not fixed, as they will move according to wet and dry periods. Hence it is difficult to generate an accuracy estimate. It could be said that the very high vulnerability boundary would normally be within 30m of the boundary shown, but this could be greater during very dry or very wet periods.

Layers were supplied as ESRI shapefiles in CIG85 projection. In September 2003, Geoscience Australia projected these shapefiles into the MGA (GDA94) projection using an XY (X=550015, Y=8780001) shift.

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