THE MILWAUKEE COLUMN: A SIMPLE COLUMN APPARATUS FOR TEACHING GROUNDWATER FLOW AND CONTAMINANT TRANSPORT

Hydrogeology teaching labs often utilize equipment and supplies that can cost hundreds to thousands of dollars to demonstrate the fundamentals of groundwater flow and contaminant transport. In an effort to make teaching hydrogeology more accessible, our goal was to design a simplified, affordable, and effective column apparatus that helps visualize groundwater flow and contaminant transport. With a budget of no more than $100, our apparatus utilizes two Mariotte bottles to supply a steady-state influent of water with two added solute tracers (green food coloring and chloride) into a translucent column filled with fine gravel. Effluent samples are easily collected by hand and visually analyzed to create a dye-tracer breakthrough curve; the chloride-tracer breakthrough curve is optional for labs already equipped with a bench-top ion-specific electrode and a multi-meter. The calculated mean arrival time of the tracer(s) can be compared to the estimated mean arrival time as predicted by Darcy’s law from volumetric flow rate, cross-sectional area, and porosity. Prototypes of the Milwaukee Column have been constructed and tested and current research is focused on downscaling the apparatus size and increasing its visualization. A ready-to-use version of the $100 Milwaukee Column is expected by the beginning of the new calendar year of 2022.