NSW Department of Land and Water Conservation
PO Box 2185, Dangar, NSW, 2309
Phone (02) 4960 5019, Fax (02) 4960 5042
Estimates of the area of land in NSW currently affected by dryland salinity range from 120,000ha to 174,000 ha (NSW Government, 2000), and this will increase substantially if current landuse practice continues. Identifying the more significant groundwater recharge areas across the catchment is an essential first step in dealing with the causes, rather than the effects, of salinisation processes. It is also the foundation for catchment scale planning by Catchment Management Boards and other bodies, which will have far-reaching implications for landuse and vegetation management now, and in the future.
Recharge areas can be assessed from direct physical measurement (which is labour intensive, expensive, and usually point-source data); from hydrologic and geospatial modelling (which usually has long development times); or from a more qualitative, but quicker, approach using a GIS. The GIS-based approach was used in this project to produce broadscale recharge maps for catchment-scale planning. The method draws on existing information (climate, landuse, soil conditions and hydrogeology) to provide a first approximation for defining recharge areas across NSW.
The Hunter catchment, in eastern NSW, has been used to trial this approach. Initial results, based on a simple recharge model, have been calibrated against more detailed information, based on soil landscape mapping, using a data modelling approach. The results have then ‘validated’ against a separate area (with good data coverage), before application across the catchment. The methodology is outlined in detail, and recharge maps described. This approach has also been used in the Lachlan catchment, in southwest NSW. Whilst the results obtained are no substitute for detailed hydrologic assessment (and other limitations also need to be addressed), they can provide timely information for community groups for use in catchment-scale planning.
NSW Government (2000). Taking on the challenge. NSW Salinity Strategy. ISBN 0 7347 5146 X. NSW Department of Land and Water Conservation.