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

This Article Figures Only 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 Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Ochsner, T. E. Articles by Wang, Q. Search for Related Content PubMed Articles by Ochsner, T. E. Articles by Wang, Q. Agricola Articles by Ochsner, T. E. Articles by Wang, Q. Related Collections Soil Physics Heat Transport Soil Methods/Instrumentation

Soil Physics

Evaluation of the Heat Pulse Ratio Method for Measuring Soil Water Flux

^a USDA-ARS, Soil and Water Management Research Unit, St. Paul, MN 55108
^b Dep. of Agronomy, Iowa State Univ., Ames, IA 50011
^c Dep. of Agronomy, Kansas State Univ., Manhattan, KS 66506
^d State Key Lab. of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling 712100, China, and Institute of Water Resources Research, Xian Univ. of Technology, Xian 710048, China

^* Corresponding author (ochsner{at}umn.edu)

Soil water flux is an important hydrologic parameter, yet few techniques for measuring it in situ are available. Here we evaluate the heat pulse ratio method for measuring water flux. We conducted heat pulse measurements of flux in packed columns of sand, sandy loam, and silt loam soil. Water fluxes were calculated from the data following both a traditional temperature increase difference method and a new temperature increase ratio method. Both methods yielded similar estimates of flux, agreeing to within 0.84 cm h^–1 on average. The low flow detection limits for both methods were also similar and ranged from 0.1 to 0.4 cm h^–1. However, the ratio method was superior in that it permitted simpler calculations, reduced the number of required parameters by four, and exhibited two to three times greater precision. We found strong linear relationships (r² 0.98, standard error < 0.4 cm h^–1) between estimated and imposed water fluxes up to 40 cm h^–1. However, the slopes of these relationships were less than one, ranging from 0.739 for the sand to 0.224 for the sandy loam. These slopes indicate that the sensitivity was less than predicted by the standard conduction–convection model. We have not discovered the cause of these errors, but we did find that the errors could not be explained by increasing the magnitude of the conduction term in the model as has been previously suggested. Instead, the errors could be explained by reducing the magnitude of the convection term. This finding can help direct future research efforts to improve the accuracy of the ratio method.

Abbreviations: DTD, dimensionless temperature increase difference • MDTD, maximum dimensionless temperature increase difference

This article has been cited by other articles:

				G. Liu, B. Li, T. Ren, and R. Horton Analytical Solution of the Heat Pulse Method in a Parallelepiped Sample Space Soil Sci. Soc. Am. J., August 27, 2007; 71(5): 1607 - 1619. [Abstract] [Full Text] [PDF]

				G. J. Kluitenberg, T. E. Ochsner, and R. Horton Improved Analysis of Heat Pulse Signals for Soil Water Flux Determination Soil Sci. Soc. Am. J., January 1, 2007; 71(1): 53 - 55. [Abstract] [Full Text] [PDF]

				J. Gao, T. Ren, and Y. Gong Correcting Wall Flow Effect Improves the Heat-Pulse Technique for Determining Water Flux in Saturated Soils Soil Sci. Soc. Am. J., March 29, 2006; 70(3): 711 - 717. [Abstract] [Full Text] [PDF]