AN INNOVATIVE EXPERIMENTAL COLUMN DESIGN FOR TEACHING THE CONCEPTS OF DARCY’S LAW AND HYDRAULIC CONDUCTIVITY

The basic understanding of how water flows below the ground surface through soil and rocks is of fundamental importance to the studies of groundwater hydrology. Darcy, a French engineer, was the first to conduct an experiment to demonstrate the relationship that exists between groundwater flow velocity, the hydraulic gradient causing the flow to occur and a constant, describing the ability of a geologic material to transmit water, also known as hydraulic conductivity. Darcy’s law is taught in almost every introductory geology, environmental geoscience, hydrology and hydrogeology class. Although the importance of hands-on learning in hydrogeology is well established, very rarely is the actual experiment used to teach this concept to our students. Often, a diagram is used to explain this concept. A recent Internet search was conducted to obtain a commercially available Darcy’s column to demonstrate his experiment in our classroom. The search was without success. Thus, we came up with an innovative experiential column design to teach Darcy’s law for the purpose of enhancing students’ learning and comprehension.

In this experiential design, transparent plastic pipes were utilized for better visualization of sediments and hydraulic head. The discharge (flow) through the column can be controlled to demonstrate that even if the flow rate through the column changes, the hydraulic conductivity remains the same. Similarly, the hydraulic heads can be manipulated by changing the angle of the column to illustrate that hydraulic conductivity remains constant, giving better understanding that groundwater flow is controlled exclusively by the total hydraulic head, not by the pressure head or by the elevation head alone. This newly developed, relatively simple and inexpensive Darcy’s column design could be utilized by educators at different levels (High School to College) to effectively teach the concept of groundwater flow.