Analyzing Plant Root - Capillary Fringe Interactions For Improved Groundwater Management

Abstract

The plant wilting point is generally believed to occur at a matric potential value of -1500 kPa for all plant species in all environments. In this study, I strive to illustrate how varied the plant wilting point can actually be and to show how using a constant value for all species may be a source of error. Matric potential values are determined through the use of the van Genuchten soil water characteristic curves, where each soil has its own curve. Additionally, the maximum depth of the groundwater table was studied. The maximum depth was determined based on the rooting depth of the plant species and the height of the capillary fringe water at the plant wilting point. Since no acceptable calculation for capillary fringe height at plant wilting could be found in the literature, my own technique is presented here. It involves the use of the capillary height equation presented by El-Kadi and Ling, which was taken as the maximum height of the capillary fringe in a soil. Then, a relationship between the volumetric water content at the plant wilting point and the capillary fringe height was developed and employed. Summing the rooting depth and the capillary fringe height resulted in the maximum depth of the groundwater table. Data was collected through a literature review and was categorized based on twelve soil types, four ecoregions, and three vegetation classes. These categories allowed me to identify patterns within subsets of data points. Based on these patterns, guidance tables for managing the groundwater table depth are presented.