Interferometric SAR for Hydrology Applications
One of the key applications of SAR is based on the fact that phase information is retained/required during processing of the imagery. As a result, it is possible to use the phase information as a sensitive measurement tool for changes in position across the image. Known generically as SAR interferometry, or InSAR, this family of techniques enables the measurement of topographic height, changes in topographic height, and changes in scattering properties within a SAR scene.
An important application of InSAR is the measurement of ground motion. Differential SAR interferometry (DifSAR) was initially demonstrated as an important tool in the observation of tectonic and volcanic deformation, as well as monitoring ice motion. More recently, DifSAR has been demonstrated within the water resource community to be a valuable tool in detecting, monitoring, and assessing ground motion arising from aquifer deformation.
Over the past Century, over-production of groundwater for both irrigation and drinking water has resulted in significant drops in water levels across the US and elsewhere. These sometimes severe water level declines (up to hundreds of meters) result in an environment in which the natural underground storage structures may temporarily or permanently deform. In the worst case, the granular skeletal structure of the aquifer system irreversibly collapses in the absence of the hydraulic pressure provided by the removed fluid. In many cases, this collapse is expressed on the ground surface as a local elevation change or subsidence. This change not only poses a significant risk to existing infrastructure, but is an indication of the health of the underlying aquifer system and water supply.
For more information, contact David Cohen