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

Core Ideas Relation between water supply and actual infiltration rates is essential for plant growth and water budget studies. A new visual method is developed to quantitatively estimate actual infiltration for students and professionals interested in water resources management education. The new visual method helps students understand complex relations between water supply and actual infiltration. The method fits the need of students in hydrology and other water resources classes in understanding the concepts of capacity and actual infiltration.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.