ABSTRACT
Information on the temporal and spatial variation of the water content of soil and other porous materials is central to understanding and managing a host of hydrologic, environmental, meteorological, agricultural, engineering, and industrial processes. It has long been recognized that reliable, robust, and automated techniques for the in situ monitoring of soil-water content in these varied processes can be extremely useful, if not essential. Over the past 70 years this recognition has fostered the investment of a considerable amount of ingenuity in developing such techniques.
