Water Content

Direct or indirect measures of soil water content are needed in practically every type of soil study. Water content as usually used in soils work is either a dimensionless ratio of two masses or two volumes or is given as a mass per unit volume. Water content measurements by gravimetric methods involve weighing the wet sample, removing the water, and reweighing the sample to determine the amount of water removed. This chapter deals with measurement of water content or inferences of water content. Neutron scattering and neutron and gamma ray absorption are affected by water content of a porous material and may be adapted to water content measurement. Electrical and thermal conductivity and electrical capacitance of porous materials vary with water content. Many of the problems involved in measurement of electrical and thermal conductivity and electrical capacitance in soil are avoided by use of porous blocks containing suitable electrodes and imbedded in the soil.