Nutrient generation and transport at the catchment scale

Abstract: Transport of nutrients (e.g., phosphorus) from different land uses within a catchment can negatively impact on our water resources. Nutrient generation is frequently studied at the paddock or farm scale, while the impacts on water quality occur at the catchment scale. Scaling nutrient generation and transport between the farm and catchment is important in understanding the impacts of land-use and land-cover change on water quality. There are many challenges in bridging these spatial scales including nutrient cycling through the catchment and data availability. This paper reports on the use of the Catchment Analysis Tool (CAT) linked to 2CSalt to investigate nutrient generation and movement in the Latrobe River Catchment. CAT uses spatially distributed characteristics including land-use, rainfall, slope and soil type, to describe hydrology, and this is coupled with a land-use based nutrient generation rate to describe nutrient mobilisation within the catchment. The study area in the Latrobe River Catchment, Victoria, Australia, contains a number of stream gauging sites, with monthly nutrient data used to validate the model outcomes. CAT linked to 2CSalt provided a good representation of catchment scale hydrology, with an acceptable coefficient of efficiency for stream flow at all ten gauges (>0.6). Nutrient generation rates based on published literature for each land-use category resulted in a good prediction of total nitrogen and total phosphorus