Establishment of a harmonized tool for calculating river discharge and nitrogen loads from unmonitored areas in Denmark

Abstract

The main objective of the present study is to detect and assess empirical relationships between river discharge and catchment characteristics to support the simulation of nitrogen losses on the regional and national scale. The empirical model derived provides the basis for a comprehensive and harmonized tool for the calculation of annual river discharge and nutrient loads from 49 Danish catchments to coastal waters. The model was applied for the years 1994 and 1995. Results from this application indicate that the simulated values are generally lower than the corresponding values from previous estimations. The main explanation is that precipitation as the most important model parameter shows a distinct gradient towards the coastal areas. This gradient has not been considered by the previously applied regional methods. Although the model results are generally reasonable, improvements are necessary, particularly with respect to the representation of subsurface properties.