VISUALIZING GROUNDWATER FLOW BY MODIFYING A LABORATORY FLUME FOR USE AS A DARCY TUBE

Studying groundwater flow can help students understand contamination issues and remediation efforts, as well as to develop an appreciation for keeping potable aquifers clean. Well fields have been installed to analyze groundwater flow in aquifers, but these do not allow users to see flow through the aquifer, and their use relies, in part, on storm pulses for data. Well-field construction is expensive and the unpredictability of weather patterns creates potential scheduling issues for classes. In the lab, Darcy tubes are commonly used to measure hydraulic conductivity, water retention and many other factors influencing groundwater flow without relying on a storm pulse. Here, we present our initial efforts to simulate Darcy flow in a laboratory flume that was modified to enable experiments at a larger scale. We created a large confined aquifer that allowed for precise grain-size characterization of different stratigraphic layers, measurement of both horizontal and vertical conductivity, and discharge measurements. The design also allows for introduction of “contaminants” (food coloring) so that students can visualize a contaminant plume. PVC piping, PVC valves, Plexiglas, and silicon caulk were used to build the flume Darcy tube. Plexiglas was used to enclose the flow, creating a confined aquifer, while PVC valve piping at each end of the tube regulated the flow. Stratigraphic layers of different grain sizes were used to more realistically simulate natural conditions. Plexiglas tubes (“wells”) were fitted through the upper confining Plexiglas lid and installed into each layer of sediment to enable visualization of artesian flow conditions, extraction and/or introduction of contaminants, and measurement of vertical conductivity. This design can be useful in introductory level classes and community outreach to help students and the public visualize groundwater flow and contaminant transport, and in advanced undergraduate classes to illustrate the Darcy experiment and enable students to measure head changes, discharge and conductivity.