In the past two decades groundwater workers have relied chiefly on new specific quantitative data. Yet, hydrogeologists should get advanced knowledge from looking and thinking backward at geologic and hydrogeologic phenomena and processes and then working forward from known or assumed causes to effects. This basic scientific method of retrodictive linkage represents interpretation and explanation of past actions and events inferred from laws that are assumed to have governed them. Retrodictive linkage can be derived from a cognitive network that includes (1) a concise store of key generalizations and inferences, (2) assignment of qualitative values to key factors, and (3) arrangement of interrelations of factors that lead by inference to useful associations and patterns. Skillful application of retrodictive linkage allows needed information to be derived synergistically before new data are collected.

Excessive emphasis on quantitative data may produce a mindset that limits reasoning for retrodictive linkage. In logical narrative form, a needed Prior Conceptual Model Explanation (PCME) can be systematically and reliably prepared quickly by using retrodictive linkage. This method allows early perspective and high synergistic value with existing information. Linkage of interrelated factors provides interlocking evidence that reasoning is on the right track. The PCME has primary use as input into detailed studies and for explanation of hydrogeologic conditions to non-experts.

An example on the retrodictive linkage method is presented with application to the complex hydrogeology of the fractured-rock region of the Southeastern States, producing a generic conceptual model and an early plateau of knowledge of a site not attainable in other ways.