Risk mapping of phosphorus leakage - improved method using a Digital Elevation Model

Abstract: Eutrophication is an ongoing problem in the Baltic Sea and is therefore found as a topic of the Baltic Sea Action Plan as well as the environmental goals of Sweden. One source to eutrophication is the leakage of phosphorus from agricultural lands. This study was aimed to map risk areas of phosphorus leakage from surface runoff in a catchment located in the southern parts of Sege river, Scania. The process of mapping risk areas was carried out both with and without preprocessing a digital elevation model by filling sinks and the outcome of the two methods was compared against each other. Flows of clay rich sediment in and out of a sedimentation dam located in the study area was compared with climate data over a period of 4 months. The results indicate that highest risk of surface runoff erosion is in an area in the south, where clay content is 35-40 % and the topography highly varying with several natural depressions. The origin of clay rich sediments from surface runoff erosion was best shown by analysis on a filled digital elevation model. Correlation values of single climate parameters with measured phosphorus leakage were weak but indicate that the risk periods may be best described by the combined effect from several parameters.