Models play a key role in advancing our understanding of how the Critical Zone forms, operates, and evolves. CZOs provide an important opportunity to improve various models by using integrated measurements to parameterize, test and develop new representations of CZO processes.  The CZOs seek to extend and improve process specific models, such as the response of vegetation to water stress, as well as fully coupled models of atmospheric-hydrologic-ecologic and geomorphic processes. Comprehensive data sets from the CZOs provide a unique opportunity to evaluate models at different temporal and spatial scales and across a range of environmental settings. Models also provide a mechanism to generalize and extend observation-based results beyond the CZOs. CZO models will allow the prediction of the Critical Zone response to future climate and land use changes.The CZO modeling strategy can be generally categorized by two approaches: conceptual and numerical models.