Starting as a research project in 1996, a national water resources model (DK-model) was developed by the Geological Survey of Denmark and Greenland to advance the assessment of groundwater quantitative status accounting for interactions with surface water and anthropogenic changes, such as extraction strategies and land use, as well as climate change. Through continuous development the model is gradually improved and increasingly applied by research projects and for decision support e.g. the Danish implementation of the EU Water Framework Directive (WFD) as well as other decisions related to protection of water resources (quantitative and chemical status), ecosystems and the built environment.
The DK-model is a mechanistically, transient and spatially distributed groundwater-surface water model. It includes a 3D hydrogeological description of the entire 43.000 km2 in Denmark, initially based on a national interpretation, but gradually updated based on detailed studies by regional water authorities and other national research institutions. By incorporating new knowledge, the model is kept up to date and ensures a common basis for assessments at various scales by different authorities.
The hydrological interpretation has been utilised in a 3D georeferenced delineation of groundwater bodies and aquifers for the entire country. Linking the model to the national database on groundwater extraction and chemical analysis, assessments of groundwater quantitative and chemical status at the groundwater body level, required for the implementation of the WFD, have been made possible.
Since the first application of the DK-model in 2003 to assess the national exploitable groundwater resource, the model has constituted an essential tool in the quantitative assessment and regulation at national and regional levels. Utilising predicted climate changes the model has further been applied to estimate future changes in groundwater levels and recharge at national scale. These results have been used by local authorities in a screening phase for formulating climate change adaption strategies. Combining the DK-model with supplementary models on nitrogen leaching and retention in surface water systems, the DK-model is the backbone of national model on nitrogen transport, supporting the national regulation on nitrogen.
Core publications on the construction and update of the model:
Højberg AL, Troldborg L, Stisen S, Christensen BSB, Henriksen HJ (2013) Stakeholder driven update and improvement of a national water resources model. Environmental Modelling & Software 40, 202-213.
Henriksen HJ, Troldborg L, Højberg AL, Refsgaard JC (2008) Assessment of exploitable groundwater resources of Denmark by use of ensemble resource indicators and a numerical groundwater–surface water model. Journal of Hydrology, 348, 224-240
Henriksen HJ, Troldborg L, Nyegaard P, Sonnenborg TO, Refsgaard JC, Madsen B (2003). Methodology for construction, calibration and validation of a national hydrological model for Denmark. Journal of Hydrology, 280(1-4), 52-71
Publications on the application of the model:
Olsen M, Troldborg L, Henriksen HJ, Conallin J, Refsgaard JC, Bøgh E (2013) Evaluation of a typical hydrological model in relation to environmental flows. Journal of Hydrology 507, 52-62.
Rasmussen J, Sonnenborg TO, Stisen S, Seaby LP, Christensen BSB, Hinsby K (2012) Climate change effects on irrigation demands and minimum stream discharge: impact of bias-correction method. Hydrology and Earth System Sciences 16, 4675-4691.
Seifert D, Sonnenborg TO, Refsgaard JC, Højberg AL, Troldborg L (2012) Assessment of hydrological model predictive ability given multiple conceptual geological models. Water Resources Research 48(6) W06503.
Sonnenborg TO, Hinsby K, van Roosmalen L, Stisen S (2012) Assessment of climate change impacts on the quantity and quality of a coastal catchment using a coupled groundwater-surface water model. Climatic Change 113(3), 1025-1048.
Stisen S, Højberg AL, Troldborg L, Refsgaard JC, Christensen BSB, Olsen M, Henriksen HJ (2012) On the importance of appropriate precipitation gauge catch correction for hydrological modelling at mid to high latitudes. Hydrology and Earth System Sciences 16, 4157-4176.
Sonnenborg TO, Christensen BSB, Nyegaard P, Henriksen HJ, Refsgaard JC (2003). Transient modeling of regional groundwater flow using parameter estimates from steady-state automatic calibration. Journal of Hydrology, 273(1-4), 188-204