A New Visual Method to Determine Infiltration Rate from Infiltration Capacity Models

Abstract

It is challenging to demonstrate the ideas of infiltration capacity and actual infiltration rates into soil from a water supply (such as rainfall) event because infiltration capacity models are usually given as a function of time. This article outlines a new visual method by which the actual infiltration rate can be demonstrated using an Excel spreadsheet file. The visual method is appropriate for junior/senior and graduate students interested in water resources management courses such as hydrology, groundwater engineering, or soil physics. The first step is to construct a relationship between the capacity infiltration rate and the cumulative infiltration depth. This relationship serves as the basis to determine the actual infiltration rate. The next step is to use a visual iterative approach in Excel to determine the timing of runoff and the actual infiltration rates. Three representative examples are presented to illustrate the method. The first example represents a case of constant water supply rate. In the second example, we present a scenario with unsteady water supply rate, but having large enough rate to sustain continuous runoff once it started. The third example is a case of unsteady water supply rate with intermittent runoff after it started. This new approach is a valuable tool by which students and researchers can better understand the concepts related to infiltration capacity and actual infiltration rate in real-world applications. Impact Statement Relationships between water supply rates and actual infiltration rates into a soil are important concepts of many real-world applications. This article outlines a new visual method by which the actual infiltration rate can be determined using a spreadsheet file in a trial-and-error manner. With this new method, the infiltration and runoff concepts can be quantitatively demonstrated to better understand the difference between the infiltration capacity and actual infiltration.