Indicators of Catchment Condition in the Intensive Land Use Zone of Australia – Rivers in salt hazard

It should be noted that this data is now somwhat dated! The proximity of parts of a river network to saline soils is an indicator of the propensity for saline river flows. This information can be used to guide catchment scale planning and management towards land management practices to maintain water tables at depths well below the surface in near-stream areas. Sensitivity is a function of how rapidly land-use changes cause hydrological changes affecting stream flow and groundwater conditions.

The most detailed river data available is the AUSLIG 1:250K TOPO data. This scale is appropriate to catchment scale analyses and has been used for this indicator. The saline soils coverage is derived from the Atlas of Australian Soils (Northcote, 1968), which was mapped at 1:2M scale.

This indicator is calculated as length of stream draining saline soils divided by total length of stream. The quality and reliability of the data set is limited by the coarseness of the soil mapping.

Broadly, it is reasonable to expect that if the sources of salt within a catchment are close to streams, stream water will be more saline than for areas where salt sources are remote from streams. However, interpretation is not unequivocal as the hydrologic connectivity of alluvial soils is not spatially uniform and the quantity of salt within asalt hazard soilsa and its availability are not defined. The indicator has not been validated against stream salinity data, but the relationship is easy to understand by users. Some level of validation could be achieved using the stream reach and exceedence data when available. The greatest density of high salt risk is in the north and west-flowing tributary catchments of the Murray and Darling Rivers, most notably the Broken River, Loddon, Avoca, Murray-Riverina, Lachlan, Mallee, Wimmera-Avon Rivers, Moonie, Gwydir, Namoi, Castlereagh, and the Macquarie-Bogan Rivers. The Gawler, Wakefield and Broughton Rivers in South Australia are shown as in the poor category (high risk). The Burdekin, Don, Calliope and Boyne River basins in Queensland have an indicated moderately poor condition. The upper reaches of the Greenough, Blackwood and Avon River Catchments (WA) have a relatively poor condition.

Data are available as:

• continental maps at 5km (0.05 deg) cell resolution for the ILZ;
• spatial averages over CRES defined catchments (CRES, 2000) in the ILZ;
• spatial averages over the AWRC river basins in the ILZ.

See further metadata for more detail.