Groundwater modeling of Krycklan catchment and evaluation of the groundwater discharge distribution

Abstract: This thesis aimed to evaluate the groundwater discharge distribution in the Krycklan catchment by developing a groundwater flow model using COMSOL Multiphysics and assuming a topography- controlled groundwater surface. Previous research has shown that the groundwater surface can be modeled as a subdued replica of the topography in humid climate regions where the permeability of the subsurface is low and where the groundwater surface is shallow. In earlier studies by Mojarrad (2021), it has been shown that the modeled infiltration becomes higher than the observed infiltration when a topography-controlled groundwater surface boundary is used and that a solution to this is to decrease the resolution in recharge areas. This method was therefore used in the thesis; however, the modeled infiltration was unsuccessfully lowered. This is thought to be due to differences between the model and the previous study and which are discussed further in this thesis. The discharge and recharge areas were identified using the direction of the vertical component of Darcy velocity, and the discharge flow distribution was evaluated in ArcMAP. The discharge flow distribution in the landscape was compared to real geographical data of surface water to identify a discharge threshold value for when the water balance is upheld by surface water flow or by evapotranspiration. The evapotranspiration discharge flow distribution was also evaluated, where the highest flow values were found in riparian zones of the landscape.