lecturers-ankerAnker Lajer Højberg, Ph.D., is a Senior Researcher in the department of hydrology at the Geological Survey of Denmark and Greenland. His research covers a broad range of topics related to hydrology and groundwater, including model development, calibration and uncertainty assessments varying from small scale reactive transport to national scale assessments. He has participated/coordinated numerous national and international research projects primarily related to modelling and the implementation of the EU Water Framework Directive (WFD). For more than ten years he has managed the development of the Danish national water resources model and has recently lead the development of a Danish national nitrogen model. In addition to a close collaboration with Universities in research projects and supervision of master and PhD students, he has been supervising the Danish regional and national water authorities in the implementation of the WFD. In recent years Dr. Højberg has focused his research on transport and fate of nitrogen at various scales and how to introduce scientific based knowledge into legislation and is presently coordinating the research project TReNDS on nitrogen transport.

Lecture description:

Combating nitrogen by accounting for natural degradation

EU member states are challenged by nitrogen loads to groundwater and estuaries/inland freshwater systems impeding the achievement of good ecological status as required by the Water Framework Directive (WFD). Nitrogen regulation are commonly based on uniform regulation imposing the same restriction for all areas independent on drainage schemes, hydrogeochemical conditions in the subsurface and retention in surface waters. Recent research projects have, however, illustrated that natural degradation of nitrogen may be significant but with large spatial variations depending on the physical and biogeochemical conditions. A much more cost-effective regulation of nitrogen is thus possible if areas with high and low reduction can be identified, allowing to differentiate regulation putting most restrictions and mitigation measures in areas, where nitrate leaching is high and natural nitrogen reduction is low. Present challenges include the mapping of spatial variability in natural nitrogen degradation at sufficient small scale and with sufficient accuracy and the development of a concept by which the natural degradation can be accounted for in the regulation of nitrogen. These issues have been the topics for several recent research and innovation projects in Denmark, and the talk will draw on experiences and results from these studies.