Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 8, 4045-4067, 2015
https://doi.org/10.5194/gmd-8-4045-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Model description paper
21 Dec 2015
Coupling global models for hydrology and nutrient loading to simulate nitrogen and phosphorus retention in surface water – description of IMAGE–GNM and analysis of performance
A. H. W. Beusen1,2, L. P. H. Van Beek3, A. F. Bouwman1,2, J. M. Mogollón1, and J. J. Middelburg1 1Department of Earth Sciences – Geochemistry, Faculty of Geosciences, Utrecht University, P.O. Box 80021, 3508 TA Utrecht, the Netherlands
2PBL Netherlands Environmental Assessment Agency, P.O. Box 303, 3720 AH Bilthoven, the Netherlands
3Department of Physical Geography, Faculty of Geosciences, Utrecht University, P.O. Box 80.115, 3508 TC Utrecht, the Netherlands
Abstract. The Integrated Model to Assess the Global Environment–Global Nutrient Model (IMAGE–GNM) is a global distributed, spatially explicit model using hydrology as the basis for describing nitrogen (N) and phosphorus (P) delivery to surface water, transport and in-stream retention in rivers, lakes, wetlands and reservoirs. It is part of the integrated assessment model IMAGE, which studies the interaction between society and the environment over prolonged time periods. In the IMAGE–GNM model, grid cells receive water with dissolved and suspended N and P from upstream grid cells; inside grid cells, N and P are delivered to water bodies via diffuse sources (surface runoff, shallow and deep groundwater, riparian zones; litterfall in floodplains; atmospheric deposition) and point sources (wastewater); N and P retention in a water body is calculated on the basis of the residence time of the water and nutrient uptake velocity; subsequently, water and nutrients are transported to downstream grid cells. Differences between model results and observed concentrations for a range of global rivers are acceptable given the global scale of the uncalibrated model. Sensitivity analysis with data for the year 2000 showed that runoff is a major factor for N and P delivery, retention and river export. For both N and P, uptake velocity and all factors used to compute the subgrid in-stream retention are important for total in-stream retention and river export. Soil N budgets, wastewater and all factors determining litterfall in floodplains are important for N delivery to surface water. For P the factors that determine the P content of the soil (soil P content and bulk density) are important factors for delivery and river export.

Citation: Beusen, A. H. W., Van Beek, L. P. H., Bouwman, A. F., Mogollón, J. M., and Middelburg, J. J.: Coupling global models for hydrology and nutrient loading to simulate nitrogen and phosphorus retention in surface water – description of IMAGE–GNM and analysis of performance, Geosci. Model Dev., 8, 4045-4067, https://doi.org/10.5194/gmd-8-4045-2015, 2015.
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Short summary
The IMAGE-Global Nutrient Model (GNM) is used to study the impact of multiple environmental changes on N and P delivery to surface water and transport and in-stream retention in rivers, lakes, wetlands and reservoirs over prolonged time periods. N and P are delivered to water bodies via diffuse sources (agriculture and natural ecosystems) and wastewater. N and P retention in a water body is calculated on the basis of the residence time of the water and nutrient uptake velocity.
The IMAGE-Global Nutrient Model (GNM) is used to study the impact of multiple environmental...
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