Remote sensing of soil moisture in an arid to semiarid environment

Microwave radar has potential for remote sensing of surface soil moisture. Synthetic aperture radar (SAR) platforms have been used to infer soil moisture from SAR data. The large difference between the dielectric constant of soil and water form the basis for radar soil moisture sensitivity. Soil moisture is affected by precipitation, and in turn affects infiltration, runoff, evaporation and surface albedo. A technique to assess soil moisture with radar images is significant because soil moisture is a key parameter in climatic, agricultural, and hydrological studies. For example, improved techniques for measuring soil moisture are needed to provide temporal and spatial data for hydrological runoff models designed for and to semiarid environments.; This research explores the sensitivity of synthetic aperture radar (SAR) to soil moisture in an and to semiarid environment. The study area is located on Winnemucca Lake, a playa in western Great Basin, Nevada. Two C-band radar images from the RADARSAT satellite are used in conjunction with field collected soil moisture samples. Geostatistical georeferencing is used as a tool to register field soil moisture samples to the radar images. The two images coincide with both a dry and a wet climatic period. The July 30, 1999 image and field soil samples were collected during a dry period with low moisture contents. The August 09, 1999 image and field soil samples were collected after a rainfall that produced higher soil moisture contents. In contrast with the July radar image, the August image shows higher radar return, indicating the sensitivity to soil moisture. Further analyses were performed to correlate soil moisture to the radar response, specifically to evaluate the different responses of the radar to the low and high moisture contents. The July and August data correlate well along a similar regression line of radar response and soil moisture.; A corollary analysis is performed to evaluate the enhancement of geomorphic features in radar images with increased soil moisture contents. This analysis is designed to explore geomorphic mapping with radar and climate conditions. The study is based on the enhancement of shoreline features and a wash canyon along Winnemucca Lake in the August image (relative to the July image). The research demonstrates that increased soil moisture generates sharper tonal changes and patterns, and consequentially improves delineation of these geomorphic features.