COMPLEXITY: THE CHALLENGE OF FORGETTING WHAT WE KNOW

Much of what we know about hydrogeological systems has come from creating simple idealizations of a much more complicated world. To wit, is the simplistic view of aquifers or regional groundwater flow systems. We operate under the assumption that complicated systems and process can be vastly simplified to aid understanding and analysis, while preserving the essential functional of the real-world system. Yet, this assumption is wrong and, more seriously, has stifled the evolution of new ideas. For example, a common understanding of lake/groundwater interactions has come from Tom Winter’s classic paper on the steady-state patterns of flow in the vicinity of lakes. Yet, lakes are unquestionably more complicated, as our detailed simulation results with HydroGeoSphere indicate. For example, temporal variability in lake chemistry or bottom-sediment properties can profoundly influence patterns of groundwater flow and the hydrologic function of lakes. Admitting lakes to be much more complicated has profound implications for the way lake archives can be interpreted in paleoclimate reconstructions. The simple view that contaminant plumes evolve as a consequence physical mass transport, as modified by retardation or kinetic decay, overlooks many levels of complexity. Our sand-tank modeling and reactive transport modeling with RetrasoCodeBright illustrate just how complex the coupling can be when reactions operate. An example is the simple case of the behavior of a dilute Fe(ClO₄)₃ solution, as it moves through a medium created by glass beads and crushed calcite. The spatial distribution of many aqueous species is coupled to the evolution of a reaction zone. Moreover, the shape and hydraulic properties of the reaction zone evolve in a complex manner depending upon the porous medium and other features. These examples suggest that the complexity of the real world is largely unappreciated and ignored. It is time to step out and to understand the vast implications of complexity. Unaccounted complexity in the behavior of lakes will change the way we think about paleoclimate reconstructions. Understanding of the behavior of plumes remains an elusive dream unless these spatially sophisticated and complex systems are studied in a realistic manner.