Making process-based knowledge useable at the operational level: a framework for modelling diffuse pollution from agricultural land

In much of Western Europe, Northeast US and parts of Australia, increased inputs of nitrogen and phosphorus to land in the form of fertilisers, manures and biosolids means that agricultural runoff now comprises a greater share of these nutrients in rivers and lakes and associated water quality problems. While numerous site-specific field studies have quantified the potential export of nutrients in agricultural runoff, it is clear that to meet the requirements of end-users, the research effort needs to shift towards developing generic models of diffuse source pollutant export from land that are based on expert knowledge but remains simple to use and easy to apply. Data-hungry process-based models, while elegant and all-encompassing, may not be suitable for the simple decision support frameworks required by end-users such as government agencies, water utilities and farmers.