Integrated surface-subsurface hydrological modeling of an agricultural plot affected by salinization

Understanding the hydraulic properties of the vadose zone, crucial for understanding water movement dynamics in agricultural areas with diverse soil characteristics. Catchment hydrology (CATHY) is considered as an effective tool for the estimation of soil-water dynamic behaviours comparing to field observations such as volumetric water content (VWC), soil-water pressure head (ψ) and groundwater table (h). The laboratory-derived results underwent rigorous validation through the Rosetta model and the Multipoint Triangle method. The primary aim of this study is to incorporate both hydraulic and Van Genuchten (VGM) parameters in the simulation and to optimize each parameter to achieve the best model performance by calibrating the model through SCE-UA method in the research site area of a 21-ha agricultural field situated along the southern edge of the Venice Lagoon affected by salinization. The calibration was aimed at optimizing three variables of pressure head, water content, and water table at the same time, which is very challenging. As the results, the model produces calibrated hydraulic and VGM parameters with hydraulic conductivity (Ks) of silt loam of 22.4 cm/day,porosity (θs) of 0.367, n of 1.28, residual porosity (θr) of 0.0912, and inverse α of 0.229. Furthermore, the CATHY simulation provides insight into soil-water dynamics. The simulations of water content dynamics reveal discrepancies across borehole, with notable underestimations observed, particularly at certain depths. Challenges also arise in replicating pressure head fluctuations due to data gaps. In water table comparisons, it initially shows underestimations but gradually increase over time. Statical analysis of Kling-Gupta Efficiency (KGE) index highlights varied model performance, emphasizing the importance of continuous data collection and comprehensive modeling approaches for understanding and managing hydrological processes of soil-water dynamics in heterogeneous geological environments. Overall, ongoing efforts are essential to enhance the model’s accuracy in capturing soil-water dynamics in the vadose zone. Keywords: CATHY, soil-water dynamic, KGE index, hydraulic parameter, VGM parameters, SCE-UA method, Rosetta model