Roles of land use resolution and unit-area load rates in assessment of diffuse nutrient emissions

• Published in: Journal of environmental management Vol. 69; no. 1; pp. 39 - 46
• Main Authors: Baginska, Barbara, Pritchard, Tim, Krogh, Martin
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.09.2003; Elsevier; Academic Press Ltd
• Subjects: Agriculture; Animal, plant and microbial ecology; Applied ecology; Australia; Biological and medical sciences; Bootstrap; Cities; Diffuse nutrient emissions; Ecotoxicology, biological effects of pollution; Emissions; Environmental Monitoring; Environmental Pollutants - analysis; Freshwater; Fundamental and applied biological sciences. Psychology; General aspects; Land use; Models, Theoretical; Nitrogen - analysis; Nutrient generation rates; Phosphorus - analysis; Terrestrial environment, soil, air; Unit-area load model; Australia; New South Wales; Oceania; North America; Europe; Bootstrap; Unit-area load model; Nutrient generation rates; Diffuse nutrient emissions; Emission; Confidence limit; Phosphorus; Trophic status; Nitrogen; Environmental management; Land use; Watershed; Nutrient; Models
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/S0301-4797(03)00112-9

In contrast to its counterparts in Europe and North America, the Australian National Pollutant Inventory (NPI) includes estimates of aggregated emissions of nutrients (total nitrogen and total phosphorus) from catchments and facilities. Sparse or inadequate data limit the extent to which nutrient exports may be estimated from direct observations. The paucity of data for calibration and simulation limits the use of sophisticated models in most Australian catchments. Therefore, a simple unit-area load model—Catchment Management Support System (CMSS)—was selected to estimate aggregated catchment emissions for the NPI. Estimates from models like CMSS are sensitive to spatial and categorical resolution of land uses identified within the catchment and to nutrient generation rates selected for each land use category. Using three Hawkesbury–Nepean subcatchments, we show that while high spatial resolution of land use mapping is useful, only four or five major land use categories with carefully selected generation rates were required to estimate potential nutrient exports sufficiently well and to determine subcatchments contributing most. Nutrient emission estimates proved to be highly dependent on selection of generation rates so a bootstrap technique was adopted to reduce subjectivity and to improve estimates of confidence limits. This led to a specification of new generation rates for Natural, Unimproved pasture, Rural and Urban land uses and to establishment of uncertainty limits.