Eleen Poeter’s lecture, “All Models Are Wrong: How Do We Know Which Are Useful?” detailed how the groundwater profession is searching for appropriate approaches to developing conceptual models, evaluating which are useful, and describing the uncertainty associated with their predictions. Formulation of a reasonable set of alternative conceptual models coupled with quantitative representation is critical to the process, but is unfortunately more difficult than numerical modeling as it must address the realm of human nature and judgment. In addition, the problem is exacerbated by the dense, opaque character of the subsurface that makes data acquisition expensive, causing the work to be accomplished with sparse, uncertain information. Nevertheless, movements to meet this challenge are gaining momentum in the groundwater profession. Poeter’s presentation discussed available practical approaches to the problem in down-to-earth terms, as well as addressed future challenges.