Development and validation of a nation-scale framework to characterize the fate and transport of key agricultural contaminants

A hydrological framework encompassing nitrogen (N), phosphorus (P) and microbial (E. coli) transfer from land to water was developed to provide a consistent and rapid approach for assessing the potential impacts of land activity on water quality in New Zealand. Application of the framework in four catchments highlighted the importance of local catchment knowledge of dominant hydrological processes that was needed to ensure flow partitions derived were a realistic representation of transport processes. Additional refinements are needed to improve process representation (e.g. effects of groundwater lags) and ensure input data (e.g. soil attributes) have appropriate resolution to describe hydrological pathways. We contend that such a framework would provide a consistent and relatively rapid approach for identifying contaminant transfer pathways from land to water that can inform assessments of the potential consequences of land use change and intensification.