Monitoring Changes in Total and Unfrozen Water Content in Seasonally Frozen Soil Using Time Domain Reflectometry and Neutron Moderation Techniques

Abstract

This paper presents the results of a study utilizing time domain reflectometry and the neturon moderation technique to monitor changes in total water content and unfrozen water content during fall, winter, and spring on a sandy loam site which was maintained snow free to maximize seasonal frost penetration. Soil temperatures were recorded continuously, and meteorological conditions were observed at a nearby climatological station. The procedure of combining the neutron probe and time domain reflectometry employed here showed good potential for augmenting the limited data on soil moisture redistribution in freezing soils under natural conditions. The data indicated the importance of obtaining a representative spatial average of water content measured with time domain reflectometry in order to obtain a good correspondence with neutron probe observations.