Modelling the Water Flow Dynamics in a Subsurface Drained Agricultural Landscape Characterized By Spatial Variability in the Geological Stratified Heterogeneity.

The HYDRUS 2D software package had been used to produce a hydrogeological model for simulating the water flow dynamics across hydro-topographical gradients and drainage sequences in a Danish morainic subcatchment (605 ha) characterized by spatial variability in the geological stratification. The studied catchment was divided into different drainage catchments based on the hydro-topographical gradients and the interconnection between the mapped tile drainage systems. Preferential flow via macropores was known to have a major impact on drainage dynamics and water balance in the studied clayey subsurface drained agricultural field. A dual porosity model was therefore expected to be capable of simulating the expected flow process. By using HYDRUS 2D and considering the various flow patterns in the subsurface, a sequence of integrated hydrogeological models was set up for simulating the tile drain flow dynamics in the catchment. For the calibration of the model, data generated by a conducted electromagnetic survey at the study area, maps of the soil hydraulic properties of Denmark, as well as the analysis of the tile drain flow pattern from installed monitoring stations were used. The model, once calibrated, was used for the reproduction of the subsurface drainage water dynamics at the specific agricultural landscape. The output of this work together with the planned experimental work will be used as the foundation for the design of a hydrogeobiochemical model in order to simulate solute transport and nitrogen dynamics in the studied landscape. This will contribute to the generation of a valuable tool with respect to the Danish water resources management regarding the modifications of the currently performed agricultural practices in the area.