A method to model compartmentalized groundwater systems is described. The method is based on the evaluation of a data set of pore pressure measurements from vibrating wire piezometers and open standpipe piezometers. Measurements were obtained from an area of approximately 5 mi2 (13 km2). The method was developed in light of the prohibitive cost of installing instruments in each of the approximately 300 groundwater compartments in the study area. Modeling pore pressure across the groundwater compartments is accomplished through the use of reliability methods that account for the range of pore pressures by elevation and material type. The method is most applicable for modeling extensive, highly compartmentalized groundwater systems in heterogeneous material types. As the method relies solely on pore pressure measurements and does not take into account pumping rates, boundary conditions, aquifer characteristics, or other aspects for modeling a transient system, only limited forward projection of the pore pressure distribution is possible.