We coupled a land surface model (CoLM - Common Land Model) with an analysis tool (PSUADE – Problem Solving environment for Uncertainty Analysis and Design Exploration) to evaluate processes controlling water table depth (WTD) through sensitivity analysis and parameter optimization. A small set of sensitive parameters governing WTD was identified, showing subsurface runoff controls average groundwater levels, while soil properties govern variability. A stepwise calibration was then suggested to improve accuracy. This framework offers a transferable pathway to enhance groundwater simulation.