Water budget and hydrodynamic models are nearing completion for the Arthur R. Marshall Loxahatchee National Wildlife Refuge. The Refuge is a remnant of the historic northern Everglades ecosystem, and has been impacted by hydrologic modification, and elevated nutrient and mineral concentrations in inflowing water. These models will be used to provide a quantitative framework for scenario analyses and management decisions related to inflow and outflow quantities, timing, and water quality. The simple water budget model was developed as a 2-compartment (double-box) model that predicts canal compartment and marsh compartment volumes and stages. This model, implemented in an Excel workbook, was calibrated for the 5-year period of record between January 1995 and December 1999, and validated with data for the 5-year period of record between January 2000 and December 2004. Statistical analyses demonstrate the applicability of this model to predict temporal variation of water levels in both the marsh and the Refuge perimeter canals. A simplified 4-compartment water quality model has been linked to the water budget model. A complex 2-dimensional model is also being developed that will provide higher spatial resolution predictions. This project illustrates the value of simultaneously developing models at two levels of complexity.