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WATERSHED LEVEL RISK ASSESSMENT OF NITROGEN AND PHOSPHOROUS EXPORT
Citation:
Wickham, J D. AND T G. Wade. WATERSHED LEVEL RISK ASSESSMENT OF NITROGEN AND PHOSPHOROUS EXPORT. COMPUTERS AND ELECTRONICS IN AGRICULTURE 37(1-3):15-24, (2003).
Impact/Purpose:
Our research objectives are to: (a) develop new methods using satellite remote sensor data for the rapid characterization of LC condition and change at regional to national scales; (b) evaluate the utility of the new NASA-EOS MODIS (Moderate Resolution Imaging Spectrometer) leaf area index (LAI) measurements for regional scale application with landscape process models (e.g., biogenic emissions and atmospheric deposition); (c) provide remote sensor derived measurement data to advance the development of the next generation of distributed landscape process-based models to provide a predictive modeling capability for important ecosystem processes (e.g., nutrients, sedimentation, pathogens, etc.); and (d) integrate in situ monitoring measurement networks with UAV and satellite based remote sensor data to provide a continuous environmental monitoring capability.
Description:
The distribution of different types of land cover across a watershed is a principal factor in controlling the amount of nitrogen and phosphorous exported from a watershed. A well developed literature of nutrient export coefficients by land-cover class was used to model the risk of equaling or exceeding specified levels of nutrient export. The model was applied to about 1000 comparatively small watersheds mapped for the state of Maryland for environmental analysis and planning. Risk estimates generally increased from east to west, but numerous areas of high variability were evident. Risk of exceeding specified levels of nitrogen and phosphorous export were non linearly related to the amount of forest in the watershed. Risk increased more dramatically for phosphorous and nitrogen when forest dropped below about 85 and 95 percent, respectively. Bifurcations in ths nonlinear relationship were the result of the relative abundance of agriculture and urban land in the watershed. The nonlinear relationship between percentage forest and risk increased more dramatically for phosphorous and less dramatically for nitrogen when urban was relatively more abundant than agriculture. Regional-scale variation in risk is discussed in terms of its relevance to environmental management.