HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ferré, T. P. A. Articles by Simunek, J. Search for Related Content PubMed Articles by Ferré, T. P. A. Articles by Simunek, J. GeoRef GeoRef Citation Agricola Articles by Ferré, T. P. A. Articles by Simunek, J. Related Collections Soil Methods/Instrumentation Flow Experiment Design

The Effect of the Spatial Sensitivity of TDR on Inferring Soil Hydraulic Properties from Water Content Measurements Made during the Advance of a Wetting Front

Ty P. A. Ferré^*,a, Henrik H. Nissen^b and Jirka imnek^c

^a Department of Hydrology and Water Resources, University of Arizona, AZ
^b Department of Environmental Engineering, Institute of Life Sciences, Aalborg University, Denmark
^c George E. Brown, Jr., Salinity Laboratory, USDA-ARS, Riverside, CA

View larger version (76K): [in a new window]   Fig. 1. Finite element domain used to simulate the advance of a wetting front into a domain with an initial uniform pressure head of -0.5 m. The circular holes in the domain are no-flow boundaries to represent the obstruction to flow caused by a 2H(0.01) TDR probe. Schematic vertical cross-sections of 2V and 3H probes are shown as well. The rods lie in the horizontal plane for all of the probe designs.

View larger version (12K): [in a new window]   Fig. 2. The water content breakthrough curve at the midpoint of the domain with no rods present determined through forward modeling with HYDRUS-2D (Actual) and the water content breakthrough curve predicted (Fitted) based on optimized values for the saturated hydraulic conductivity and van Genuchten's (1980) and n parameters as determined by numerical inversion of the observed water contents with HYDRUS-1D.

View larger version (24K): [in a new window]   Fig. 3. The inverted soil hydraulic functions based on optimization of the actual water content at the center of the two-dimensional domain with no rods present lie within a very narrow range (region between the dashed lines) that includes the correct functions (thick lines). The fitted functions (thin lines) produce an excellent estimate of the correct functions.

View larger version (14K): [in a new window]   Fig. 4. Water content breakthrough curves at the mid-depth of the simulation domain with no TDR rods present and with 2H or 2V probes of varying rod separations.

View larger version (24K): [in a new window]   Fig. 5. The inverted soil hydraulic functions based on optimization of the actual water content at the center of the two-dimensional domain with a 2H(0.005) probe present lie within a narrow range (region between the dashed lines) that includes the correct functions (thick lines). The fitted functions (thin lines) produce an excellent estimate of the correct functions.

View larger version (17K): [in a new window]   Fig. 6. Simulated TDR probe responses compared with the actual water content breakthrough curve at the center of the domain during the advance of a wetting front without rods present. The time of arrival of the wetting front is identified as the time required to reach one-half of the total water content change, which is shown as the intersection of the horizontal dashed line with each breakthrough curve.

View larger version (29K): [in a new window]   Fig. 7. Fitted log hydraulic conductivity based on water content observations made with 2H(0.01), 3H(0.01), 2V(0.01), and 2H(0.005) probes. The thick lines show the soil parameters used in the forward model. The region between the dashed lines on each panel shows the 95% confidence interval. The thin lines show the best-fit parameters.

View larger version (27K): [in a new window]   Fig. 8. Fitted hydraulic functions based on water content observations made with 2H(0.01), 3H(0.01), 2V(0.01), and 2H(0.005) probes. The thick lines show the soil parameters used in the forward model. The region between the dashed lines on each panel shows the 95% confidence interval. The thin lines show the best-fit parameters.