“…Models are needed to quantify these fluxes, however, the inherent complexity of subsurface processes presents substantial challenges for numerical modeling and associated predictions (e.g., Beven, 2018;Gassmann, 2021), particularly in clay till settings characterized by preferential flows (Badawi et al, 2023;Villholth & Jensen, 1998). The presence of preferential flow pathways, such as macropores and root channels, creates a heterogeneous and non-uniform water content, leading to faster solute transport with less likelihood for degradation and thus potential for contamination of groundwater resources (Badawi et al, 2023;Brown et al, 2000;Karan et al, 2021;Nimmo, 2012;Rosenbom et al, 2014). A major challenge in numerical modeling of the variably saturated zone in settings with preferential flow paths is a lack of data to constrain the models adequately (N. Jarvis et al, 2007;Šimůnek et al, 2003).…”