Measurement and Modeling of Flow and Transport in Macroporous Soils

University Of California-Riverside, Riverside CA

Investigators

Abstract

0106956 Mohanty Characterization of preferential flow and transport through soil macropores and fractures is one of the biggest challenges in vadose zone hydrology. Several conceptual models have been developed with different levels of complexity (e.g., equivalent continuum, dual porosity, and dual permeability approaches) to describe the macropore flow-transport process. However, no congruent conceptual model with a corroborating measurement technique is available to precisely describe this process. As gravity and/or capillary forces dominate the transport processes in the porous medium near saturation, various factors contribute to the initiation of macropore flow and its intensity, including pore geometry, distribution, and continuity. In addition soil energy status, the nature of top and bottom boundary conditions and textural layering, play important roles. We propose to quantify the effects of many of these factors on preferential flow and transport in a series of carefully controlled colunm experiments using novel designs. Concurrent measurement of soil water content, water potential, and concentration across distinct "macropore" and "no-macropore" regions, as well as of the volume and concentration of inflow and outflow with high temporal resolution, are some of the new features of our proposed study. Artificial macropores with known geometry, distribution, and initial/boundary conditions will make the data analysis and interpretation more thorough and meaningful. Several existing or newly developed conceptual models will be tested with the new data sets, ultimately leading to the formulation of more realistic preferential flow models that contain physically-based and measurable parameters. Findings of this research in ten-ns of different combinations of initial conditions, boundary conditions, macropore geometry and continuity, and other (controlled) flow and transport conditions that trigger, sustain, accelerate/decelerate or discontinue the fast flow-transport phenomenon will be valuable for better understanding and quantification of hydrologic and environmental processes at different scales.