THE USE OF SPACEBORNE INSAR FOR STATEWIDE MONITORING OF GROUNDWATER LEVELS IN CONFINED AQUIFERS

The extensive drought that has occurred in the United States over the last 10 years has led to increasing reliance on groundwater from deeper confined aquifers. In order to effectively manage these deeper aquifers, temporally and spatially dense measurements of head levels are needed, especially in agricultural areas dependent on groundwater pumping. Our recent study showed that land deformation measurements derived from L-band ALOS Interferometric Synthetic Aperture Radar (InSAR) data can be used to map confined aquifer storage properties and head levels over a 4,500 km² agricultural basin in the San Luis Valley (SLV), Colorado. To reduce the impact of vegetation on the signal, a phase interpolation between high quality InSAR pixels was employed. Here we demonstrate that the same strategy can be applied to process C-band InSAR data, which are more seriously impacted by vegetation. Using the aquifer storage properties independently derived from L-band ALOS data and well data, we transformed the C-band Envisat InSAR deformation time series to head level variations. We found that our estimated head levels were consistent with all available well records where confined aquifer pumping activity dominates. These results validate that the elastic aquifer storage properties do not vary significantly over time and space allowing us to combine InSAR data acquired from multiple missions to track head level variations over a 20-year time. The technology developed in this study can be employed to monitor groundwater levels in confined aquifer over the entire Texas in the near future.