Data used to produce the predicted pH map for the Cadna-owie - Hooray Aquifer in the Hydrogeological Atlas of the Great Artesian Basin (Ransley et.al., 2015). There are four layers in the Cadna-owie - Hooray Aquifer pH map data A. Location of hydrochemistry samples (Point data, Shapefile) B. Predicted Concentration (Filled contours , Shapefile) C. Predicted Concentration Contours (Contours, Shapefile) D. Prediction Standard Error (Filled contours , Shapefile) The predicted values provide a regional based estimate and may be associated with considerable error. It is recommended that the predicted values are read together with the predicted error map, which provides an estimate of the absolute standard error associated with the predicted values at any point within the map. The predicted standard error map provides an absolute standard error associated with the predicted values at any point within the map. Please note this is not a relative error map and the concentration of a parameter needs to be considered when interpreting the map. Predicted standard error values are low where the concentration is low and there is a high density of samples. Predicted standard errors values can be high where the concentration is high and there is moderate variability between nearby samples or where there is a paucity of data. Coordinate system is Lambert conformal conic GDA 1994, with central meridian 134 degrees longitude, standard parallels at -18 and -36 degrees latitude. The Cadna-owie - Hooray Aquifer pH map is one of 14 hydrochemistry maps for the Cadna-owie - Hooray Aquifer and 24 hydrochemistry maps in the Hydrogeological Atlas of the Great Artesian Basin (Ransley et.al., 2014). This dataset and associated metadata can be obtained from www.ga.gov.au, using catalogue number 81696 References: Hitchon, B. and Brulotte, M. (1994): Culling criteria for 'standard' formation water analyses; Applied Geochemistry, v. 9, p. 637-645 Ransley, T., Radke, B., Feitz, A., Kellett, J., Owens, R., Bell, J. and Stewart, G., 2015. Hydrogeological Atlas of the Great Artesian Basin. Geoscience Australia. Canberra. [available from www.ga.gov.au using catalogue number 79790]