Urban waterways are often associated with poor water quality. This is a result of both the altered hydrology of urban catchments and the high intensity of land use in these areas. Of particular concern is the nutrient loads entering waterways from urban systems. High nutrient loads often lead to eutrophication of receiving water bodies. Recent work on the eutrophic Lake Tuggeranong in the south of the Australian capital Territory indicated external nutrient loading from urban catchments is the major driver of eutrophication in the lake. To manage these nutrients there is a need to understand where the source.
Urban catchments are complex and include wide variety of land uses. Nutrient runoff will vary depending on the land use. In this study we investigated the nutrient loading from 27 sub-catchments that discharge into Lake Tuggeranong. Within the catchments land uses were categorised as commercial, recreational, residential, road, rural and sport. The nutrient loads from the sub-catchments were calculated and modelled against the proportion of the 6 land uses in each sub-catchment to determine if there were relationships between specific land use and nutrient loading. The relationship between the proportion of sporting fields in the sub-catchment and dissolved nutrient load was positively correlated. There were no other significant relationships between land use and nutrient loads. These findings will inform the management of nutrient loading in urban catchments and demonstrate the need to investigate urban nutrient inputs on a finer spatial scale.