Soil Physics Teaching Tools: Steady-State Water Movement in Soils

Abstract

Understanding water movement in soils is essential for understanding other soil physical processes. This generally means the introduction of Darcy's equation for saturated systems and the Darcy–Buckingham equation for unsaturated soils. Although these equations look relatively simple, they can be complex and their predictions are not always intuitive. Solving these equations can be difficult for many conditions; therefore, many aspects of water flow are presented qualitatively or omitted in texts and classes. We developed interactive Java applets that allow users to specify soil hydraulic properties and to define flow systems of interest. The software calculates the steady-state rate of water movement in those systems and displays graphs of total, matric, or gravitational potential, hydraulic conductivity, driving force, or water content in the soil as functions of position. The applets can be run from common Web browsers. An instructor can use the software to demonstrate principles while lecturing, or incorporate it into assignments, educational material, and examinations. Since the tools are available on the Web, users can access supplemental material that explains concepts. Moreover, the applets can be incorporated into Web-based decision-support systems to enhance a decision-maker's understanding of these processes. Numerical experiments utilizing the applets are available. These tools enable users to discover flow principles, calculate flow in specific systems, and gain insight into the sensitivity of water movement to hydraulic parameters needed to describe soils and flow systems. They provide a visual means of comprehending these abstract equations and the complex manner in which water moves through soils.