Interferometric Synthetic Aperture Radar (InSAR) data from multiple satellite missions were combined to study the temporal and spatial variability of head and storage properties in a confined aquifer system on a decadal time scale. The area of study was a 4,500 km2 agricultural basin in the San Luis Valley (SLV), Colorado. We had available previous analyses of C‐band ERS‐1/2 data from June 1992 to November 2000, and L‐band ALOS PALSAR data from October 2009 to March 2011. We used C‐band Envisat data to fill in the time period from November 2006 to July 2010. In processing the Envisat data, we successfully employed a phase interpolation between persistent scatterer pixels to reduce the impact of vegetation decorrelation, which can significantly reduce the quality of C‐band InSAR data over agricultural basins. In comparing the results from the L‐band ALOS data and C‐band Envisat data in a 10 month overlapping time period, we found that the shorter wavelength of C‐band InSAR allowed us to preserve small deformation signals that were not detectable using L‐band ALOS data. A significant result was the finding that the elastic storage properties of the SLV confined aquifer system remained stable over the 20 year time period and vary slowly in space, allowing us to combine InSAR data acquired from multiple missions to fill the temporal and spatial gaps in well data. The InSAR estimated head levels were validated with well measurements, which indicate little permanent water‐storage loss over the study time period in the SLV. Key Points The elastic storage properties of the SLV confined aquifer system remained stable over the 20 year time period and vary slowly in space The InSAR estimated head levels were used to fill the temporal and spatial gaps in well data The recently developed PS interpolation algorithm were successfully used to correct vegetation decorrelation artifacts in C‐band InSAR data