Assessing spatial variability in nitrate reduction by catchment scale modelling

A.L. Højberg, P.K. Engesgaard, C. Kjærgaard, B.V. Iversen, S. Jessen, I. Karlsson, R.J. Petersen, J. Koch, J.C. Refsgaard

Publikation: KonferencebidragAbstract ved konference


Regulation and management to reduce the N-loads has often been based on a uniform approach, imposing the same restrictions for all areas. However, nitrate may be reduced by natural processes in the groundwater and surface water system, but the amount of nitrate being reduced varies spatially due to natural heterogeneity in the hydro-geochemical conditions. The present trends is thus to move towards a spatial targeted approach, where restrictions are focussed towards areas, where the natural removal of nitrate is low. To support such approaches integrated large-scale models are required, which, at the same time, can be used at the regional/national scale relevant for policy and decision making, while at the same time being able to account for the small scale natural variability.

Taking the first step towards a more cost-effective regulation based on a spatially differentiated approach, a Danish National Nitrogen Model has been developed and used to prioritise the use of mitigation measures as part of the implementation of the EU Water Framework Directive (WFD) in Denmark. To further advance our understanding on the controlling processes, their spatial variability and quantify their importance the research project TReNDS Transport and Reduction of Nitrate in Danish Landscapes at various Scales ( combines detailed field studies and model simulations with focus on upscaling the process understanding to catchment scale models. Primary transport pathways considered are 1) artificially drainage, whereby nitrate is transported directly to the surface water system with limited reduction. For this alternative drain representations and calibration strategies are analysed, 2) the source-sink functioning of riparian lowlands, where the complex interaction between flow paths and reducing compounds control the reduction potential, and a new upscaling approach for quantifying the reduction are developed and tested, and 3) transport and N reduction below the redox interface, separating the oxic and anoxic parts of the subsurface, where a new method for constructing a national map of the interface and its associated uncertainty has been developed.
StatusUdgivet - 2018
BegivenhedAGU Fall Meeting 2018 - Washington, USA
Varighed: 10 dec. 201814 dec. 2018


KonferenceAGU Fall Meeting 2018


  • Programområde 2: Vandressourcer


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