Vadose Zone Monitoring
Vadose zone monitoring includes methods to measure pressure head and moisture content, as well as methods to sample pore liquids and soil gas. Vadose zone monitoring is also an integral part of many field investigations by hydrologists interested in seepage and natural recharge processes. More recently, vadose zone monitoring has become an important element of environmental assessments and remediation. Fluid potential is an important measure of the energy status of soil water. In the vadose zone, spatial differences in the potential determine the direction of soil-water movement. In direct methods, the sensor measures the fluid potential in the soil water. A tensiometer is a hydraulic device that measures the matric potential. Tensiometers and psychrometers provide the only direct measurements of soil-water potential in the field. Indirect methods, in which the soil-water potential is determined from a measurement of water content, are also commonly used in the field.