Australian Irrigation Areas (Vector), Version 1A, National Land and Water Resources Audit

This data set shows designated and actual irrigation areas in Australia compiled by the National Land Use Mapping Project of the National Land and Water Resources Audit to assist in the identification of irrigation areas in Australia. Additional data custodians include Agriculture WA, Queensland Department of Natural Resources and Mines, Murray-Darling Basin Commission, New South Wales Department of Land and Water Conservation and Tasmanian Department of Primary Industries, Water and Environment Designated irrigation areas indicate areas with administratively defined boundaries which have associated rights and obligations pertaining to use of water for irrigation. The precise meaning of the term designated irrigation area varies from region to region. aActual irrigation areasa indicate areas with observationally defined boundaries within which irrigation is practised. The boundaries have been supplied by various agencies and cover the more important irrigation areas in Australia. Users of this data set should be aware that there are irrigated areas outside the designated and actual areas shown and that there are non-irrigated areas inside them. This is particularly true of Tasmania and the Murray-Darling Basin.The data set is available in both vector and raster formats. The raster data set can be used as a companion to the 1996/97 Land Use of Australia data set which is also in raster format. Both data sets have the same coordinate system, boundary coordinates and cell size so that they can easily be overlaid. Users may find, however, that some cells are classified as irrigated by the Australian Irrigation Areas data set and as non-agricultural land by the 1996/97 Land Use of Australia data set.The Version 1a data set may be of use to researchers and policy makers in need of national, regional or local scale irrigation data, though the scale of the source material is highly variable and completness of coverage is poor in some regions.

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Lineage: The data set was constructed in vector format by appending irrigation area boundary data sets supplied by various agencies. The component data sets are listed below. One of the component data sets which was supplied as separate tiles in ArcView shapefile format was assembled into a single shapefile data set in ArcView 3.1. All other processing was carried out in ARC/INFO 7.2.1 under SunOS using double precision coordinates. For all operations in which processing used a fuzzy tolerance, the value specified was 0.00001 degrees (about 1 m). The raster form of the data set was made from the vector form. 1) Ord River Scheme, Stage 1, irrigation area boundaries. This data set was supplied by Agriculture WA in ArcView shapefile format.2) Boundary of Gazetted Irrigation Areas in Queensland. This data set was supplied by the Queensland Department of Natural Resources and Mines in ARC/INFO export file format. It shows designated irrigation areas. The coordinate datum is not known with certainty and was assumed to be the Australian Geodetic Datum 1984.3) Northern Murray-Darling Basin irrigation area boundaries. This data set was supplied by the Murray-Darling Basin Commission in ARC/INFO export file format. It shows actual irrigation areas, based on interpretation of coarse scale imagery derived from Landsat TM images. The data set comprises 11 polygons. Of these, five have not been retained in the national data set because they largely coincide with the much higher resolution polygons of the Northern New South Wales Cotton Development data set. A sixth has not been retained because it proves to be almost entirely covered by a national park and a perennial lake. One of the polygons that was retained was edited to give precedence to a higher resolution polygon in the Boundary of Gazetted Irrigation Areas in Queensland data set which it partly overlies.4) Northern New South Wales Cotton Development data set. This data set was supplied by the New South Wales Department of Land and Water Conservation, in ArcView shapefile format, as 50 separate tiles. It shows actual irrigation areas and a variety of other land uses and land covers related to cotton growing. It is based on interpretation of aerial photography and satellite imagery with extensive field checking. Only the polygons showing irrigation areas were included in the national data set. The tiles were merged in ArcView using the merge function of the GeoProcessing Wizard. Further processing was undertaken in AR