A Method for Characterizing the Vadose Zone and Monitoring Solute Transport

EPA Grant Number: R827114
Title: A Method for Characterizing the Vadose Zone and Monitoring Solute Transport
Investigators: Yeh, Tian-Chyi J.
Current Investigators: Yeh, Tian-Chyi J. , Warrick, Arthur W.
Institution: University of Arizona
EPA Project Officer: Lasat, Mitch
Project Period: October 1, 1998 through September 30, 2001 (Extended to September 30, 2002)
Project Amount: $359,955
RFA: Exploratory Research - Physics (1998) RFA Text |  Recipients Lists
Research Category: Land and Waste Management , Air , Engineering and Environmental Chemistry


The objective of this proposed study is to develop a cost-effective method for identifying distributions of heterogeneity and moisture content in the vadose zone. Scientifically, we hypothesize that information about moisture content, and pressure distributions will enhance our ability to delineate heterogeneity in the vadose zone. The arrival time of wetting or drying fronts at some depths will allow us to determine hysteretic characteristics of unsaturated hydraulic properties. We also postulate that the electrical resistivity of unsaturated porous media will have hysteresis effects and variability in the resistivity will increase as moisture content decreases and is correlated in space.


The proposed method combines a stochastic inverse approach for flow in porous media and that of electrical resistivity tomography (ERT) in an iterative manner. As a result, it can take advantage of the three-dimensional information about changes in the water content sensed by the ERT, statistical information of heterogeneity, well logs, and core samples to estimate spatially varied hydraulic properties and moisture distributions. Such a joint inversion process provides much better estimates than those could be obtained from interpreting the data types individually. Furthermore, the proposed approach is a geostatistically based estimation technique; the estimates represent the conditional mean hydraulic property fields and moisture distributions. It quantifies the uncertainty of the estimates as well as the estimates themselves. The performance of our proposed approach under realistic field conditions will then be tested.

Expected Results:

The proposed research will produce a new technology that allows us to rapidly and economically identify spatial distributions of heterogeneity and moisture or concentration in the vadose zones such that effective remediation operations can be designed and their progresses can be monitored. This tool is critical to cleanup operations at many Superfund sites. In addition, it provides means to assist risk assessment and risk management related to groundwater pollution problems.

Publications and Presentations:

Publications have been submitted on this project: View all 13 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 5 journal articles for this project

Supplemental Keywords:

hydrogeophysical joint inversion, vadose zone, risk assessment; risk management, and uncertainty., Scientific Discipline, Water, Waste, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, Physics, Restoration, Ecology and Ecosystems, Aquatic Ecosystem Restoration, Engineering, Chemistry, & Physics, Groundwater remediation, hydraulic properties, sloute transport monitoring, moisture content, solute transport monitoring, remediation, aquatic ecosystems, environmental rehabilitation, pressure distribution, groundwater contamination, electrical resistivity tomography, vadose zone, groundwater pollution

Relevant Websites:


Progress and Final Reports:

  • 1999 Progress Report
  • 2000 Progress Report
  • 2001 Progress Report
  • Final Report