TIME-DOMAIN REFLECTOMETRY AS A FIELD METHOD FOR MEASURING WATER-CONTENT AND SOIL-WATER ELECTRICAL-CONDUCTIVITY AT A CONTINUOUS PERMAFROST SITE

Time domain reflectometry (TDR) is evaluated as a field technique for measuring volumetric water content theta and bulk electrical conductiv ity sigma(b) in Arctic soils. Calibration measurements of theta and si gma(b) were carried out on three different slopes at a field site in S iberia (74 degrees 32'N; 98 degrees 35'E). Comparison of theta calcula ted from TDR using two different approaches and gravimetrically determ ined water contents shows a close correlation. TDR determined sigma(b) , applying theoretical relationships and a simple regression model, ar e compared with the electrical conductivity sigma(w) of soil solutions obtained with suction cups. Best results for sigma(w) are obtained us ing the regression model, with highest precision when probe specific c alibration is carried out. In this permafrost setting, TDR can be appl ied to obtain quantitative estimates of theta and sigma(w) in the acti ve layer. The application of the regression model in different permafr ost soils to infer sigma(w) requires additional calibration. (C) 1997 John Wiley & Sons, Ltd.