USA - Advances in nutrient source apportionment in river basins using two state-of-the-art statistical models

We will in the pre-project elucidate the two models MESAW and SPARROW. Both models relate in-stream water-quality measurements to spatially referenced characteristics of river basins, including pollution sources and factors influencing terrestrial and str eam/riverine transport. Both models empirically estimate the origin and fate of pollutants in streams and rivers, and quantify uncertainties in these estimates based on model coefficient error and unexplained variability in the observed data. The model intercomparison will be conducted through a series of two workshops. The first workshop will be held in the USA at the University of California at Berkeley, hosted by the Department of Environmental Science, Policy, and Management. This workshop will b e devoted to practical work in order to apply the two models to consistent spatial (watershed) and temporal (base year for nutrient inputs) scales. Further, we will hold a second workshop in conjunction with a MARE project meeting to be held in Paris in f all, 2005. This workshop will include a much broader suite of collaborators who are interested in nutrient fluxes, where we will refine our results to investigate uncertainty and differences in the model predictions of nutrient inputs, fate within the lan dscape and aquatic ecosystem, and loadings to the Baltic Sea. Data from the major Swedish research program MARE (Marine Research on Eutrophication - a Scientific Base for Cost-effective Measures for the Baltic Sea; http://www.mare.su.se/) will be made a vailable for the pre-project. This bilateral pre-project with one of the leading institutes in the field of water processes in USA will thus be strategically important for further collaboration.