Satellite Altimetry Applications on Land Subsidence

Water scarcity and its availability are being aggravated by anthropogenic climate change, population migration, and excessive land uses. Population growth and severe drought in California have led to a dramatic increase in groundwater demand since 1930s. Massive groundwater pumping has led to severe land subsidence, which costed the government huge sums and influenced the hydrological activities. In this study, we develop a new method using Cryosat-2 altimeter data and spatial interpolation methods to generate two-dimensional land deformation map in Central Valley, CA. Data from conventional altimetry missions (TOPEX, Jason-2, Jason-3, Envisat) are processed to generate long-term flat land subsidence (vertical motion displacement rate) time series, and to validate the Cryosat-2 derived land deformation results. The results show that the seasonal signals and flood signals are perceptible in altimetry-derived time series, and that the Cryosat-2 derived land deformation map correlate well with conventional altimetry missions (TOPEX, Jason-2, Jason-3, Envisat), in-situ cumulative groundwater level data, GPS estimated velocities, and NASA JPL InSAR estimated velocities. This is the first time a two-dimensional map is generated and used to analyze vertical motion displacement. The method of generating map is a good way to present and analyze the land subsidence trend that can be used to complement and validate other observations. A combination of multi-satellite altimetry missions can be used to detect and monitor global or regional land subsidence.