Subsurface microwave remote sensing of soil-water content: Field studies in the Negev Desert and optical modelling

The population increase in the Middle East and the respective decrease of water resources necessitate innovative methods for utilization and monitoring of water resources. Development of remote sensing tools can pave the way for remote, rapid mapping of soil-water content, control of excessive irrigation, and prevention of water waste. This paper describes a series of experiments conducted in the Negev Desert that were aimed at developing such tools for monitoring soil-water content. The use of visible near infrared and microwave techniques seems suitable. All provide good correlation with soil-water content measured on the ground. However, the microwave techniques presented here using a P-band scatterometer and ERS-2 SAR seem the most promising. Finally the possibility of optical simulation of the microwave processes is presented in an effort to improve the physical basis for empirical studies. A method of fabrication of optical samples that model soils with different water content and different surface roughness is developed, and a system for measuring backscattered signals is designed. It is shown that the reflectivity of a layered medium is a non-monotonic function of the water content. The effect of the surface roughness on the reflection from a strong buried reflector is being studied.