Nutrient Exports and Land Use in Australian Catchments

In Australia, eutrophication and reduced river flows have lead to an increase in the frequency and severity of algal blooms. To combat eutrophication, catchment managers need to assess catchment nutrient loads and, for long-term planning, annual average nutrient loads provide a sufficiently good measure. Land use is known to be an integrator of many environmental attributes that influence nutrient export, and is a simple and convenient predictor of nutrient loads. Nutrient export data from Australian studies are limited, and reference to North American data is usually necessary. In this paper we summarise the reliable Australian data on nutrient report from different broad land use types and compare them to the more extensive North American data sets. We also discuss the effects of a number of important environmental attributes on nutrient export. We conclude that while nutrient export rates are well established for North American conditions, these export rates are often significantly higher than Australian export rates and may not always be suitable for supplementing the sparse Australian data set. In addition, while the general effects of several environmental attributes (such as land slope) are fairly well established in both Australia and North America, the effects of others (such as geology) have been studied, but the results are inconclusive. The available data make it impossible to account for any environmental attribute precisely, but we propose that in some cases the data are sufficient to allow approximate adjustments to nutrient export rates. In particular, approximate adjustments can be made in certain circumstances for variations in rainfall intensity and runoff volume.