Surface Water Allocation Subareas for Western Australia were derived in consultation with the regional offices, and geometry is based on hydrographic catchments. Regional Department of Water officers identified areas of similar management requirements to define boundaries or aggregations of hydrographic subcatchments. Regions with notable management concerns both currently and possibly in the future were identified to become management subareas. Allocation subareas will be used in the calculation of sustainable yields, flow rates and ultimately these calculations will be available for water allocation and natural resource management decisions. In addition, native vegetation clearing values have been calculated for each of the subareas located within the extent of the South-West region of Western Australia, for input into the allocation process.

The Surface Water subarea data was developed in order to give a clear understanding of surface water availability and to provide management tools to make good water allocation and natural resources management decisions.