Indicators of Catchment Condition in the Intensive Land Use Zone of Australia – Suspended sediment load ratio

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It should be noted that this data is now somwhat dated!

Suspended sediment in waterways influences catchment condition by causing turbidity, usually with higher levels of salts, phosphorus and nitrogen, and more sluggish water movement. Elevated levels of salt, nitrogen and phosphorus can make streams uninhabitable for many aquatic species and reduce its quality for human uses. Turbidity restricts light transmission and can restrict photosynthesis and oxygen uptake by aquatic species. Phosphorus bound with clay particles may be released in water and with nitrogen, can lead to toxic algal blooms.

Many waterways are ephemeral but the amount of suspended sediment can have a major effect on biota that need to use this water resource opportunistically. Large waterways such as the Darling and Murray Rivers have high suspended sediment ratios but, as a proportion of the total catchment, are restricted in their overall impact on catchment condition. Increases in the suspended load of Australian streams reflect increases in rates of erosion in the wider catchment (both hillslope and channel), typically an outcome of human-induced land degradation. Turbid water adversely affects stream water quality and aquatic habitat.

The eroding areas require some level of management intervention to retard process and/or repair surface condition. The data set will be of use to researchers and policy makers in need of national or regional scale land-use data. Erosion is sensitive to land-use practice.

The data sets used to estimate stream sediment loads are the vector streams coverage generated from the AUSLIG 9eDEM data set and the 1:1 M scale National Land-Use Mapping data set (NLWRA). Data has been mapped at 1:250K. The ratio of current suspended sediment load to natural suspended sediment load is used to indicate turbidity changes in Australian rivers since European settlement.

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.