Satelllite Radar Remote Sensing of Surface Deformation for Groundwater Applications

Synthetic Aperture Radar Interferometry (InSAR) is a satellite-based remote sensing technology that is capable of measuring small deformations of the earth’s surface over large areas. In particular, InSAR has been demonstrated to be an important tool in the measurement of ground surface deformation due to aquifer system compression and expansion – with sub-centimeter accuracy. In the groundwater community it has long been recognized that excessive drawdown in poorly consolidated aquifer systems has led to irreversible aquitard compaction and serious land subsidence, often with associated ground fissuring. InSAR measurements are sensitive to ground surface displacements which often accompany or are precursors to such phenomena. As a result, InSAR data provides important input for aquifer-system characterization, groundwater modeling, and infrastructure risk assessment. Conventional surveying approaches are typically not able to attain the spatial density of measurements, over extended areas, that satellite based InSAR can. For current systems and processing techniques, deformation measurements over hundreds to thousands of square kilometers are common, with measurement intervals as fine as a few meters. With the combination of areal coverage and sensitivity, InSAR has demonstrated the ability to distinguish and delineate morphology of ground motion features unattainable using other methods, examples of which include an apparent subsurface groundwater barrier and previously unknown subsidence boundaries. What’s more, this technology provides the ability to repeat measurements on time scales from days to years, so that seasonal, inelastic, and episodic temporal evolution may be observed in detail. This presentation will provide an overview of the technology, including data sources and limitations. There will be an emphasis on current groundwater management programs that use InSAR operationally, with quantitative results from a variety of geographic locations.