Catchment characteristics predicting nitrogen and phosphorus losses in Finland

Abstract

AbstractEmpirical relationships between catchment properties and nutrient losses are often derived from spatially restricted data, which hampers the ability to more widely generalize the results. In this study, we regressed the catchment characteristics and the losses of total nitrogen (TN) and total phosphorus (TP) for all monitored catchments in Finland with adequate data (n = 59, from the year 2000 to 2011). TN loss was found to increase with the percentage of arable land and amount of point source loading and to decrease with increasing lake percentage. TP loss also increased not only with the percentage of arable land but also with fine‐grained soils (Cambisols) in the catchment and decreased with the percentage of lakes. Urban areas, scattered settlements, and N deposition were not significant explanatory variables, possibly due to their spatial covariation with arable land in Finland. Despite the fact that only a few significant explanatory variables were identified, the models explained the TN and TP losses by up to 91% and 92%, respectively.