Using interferometric synthetic aperture radar data to improve estimates of hydraulic head in the San Luis Valley, Colorado [electronic resource]

Remotely sensed Interferometric Synthetic Aperture Radar (InSAR) deformation data have recently been used to study confined aquifer systems in urban/arid areas. The deformation measured at the surface by InSAR is a consequence of changes in hydraulic head in the underlying confined aquifer system. Deformation in agricultural areas, such as the San Luis Valley, Colorado, is difficult to measure using InSAR because changes in the height of the vegetation can degrade the measurement by altering the positions of individual radar scatterers. Nonetheless, agricultural areas like the San Luis Valley are of great interest because of the link between the groundwater resources and the local economy. The San Luis Valley is an 8000 km^2 valley, located mostly on the northern side of the Colorado-New Mexico border. The valley has a vibrant agricultural economy that is highly dependent on the effective management of limited water resources. State regulation established that hydraulic head levels within the confined aquifer system should be maintained within the range experienced in the years between 1978 and 2000. Effective management of water resources in the San Luis Valley requires both seasonal changes in hydraulic head as well long term trends during this time period. In this study we had three main goals: 1) to determine if high quality InSAR data can be collected in the San Luis Valley, 2) to determine the uncertainty of the InSAR deformation measurements, and 3) to determine to what extent the InSAR deformation data can be used to improve estimates of hydraulic head in the San Luis Valley. We found that high quality InSAR data could be acquired from the San Luis Valley. Many small areas, left unwatered by the center-pivot irrigation systems, yield high quality InSAR data when processed using Small Baseline Subset analysis. The InSAR deformation measurements showed the same seasonal periodicity as the hydraulic head data from monitoring wells. The next step in our research was to more accurately determine the uncertainty in the InSAR deformation measurements. We developed a novel algorithm that uses supplementary hydrologic data to identify InSAR acquisitions whose measurements may have been corrupted with uncertainty due to atmospheric phase effects. We then proceeded to quantify the uncertainty in the InSAR deformation measurement due to decorrelation of radar signals. In the final chapter of this work we explored ways in which the relationship between InSAR measured deformation and measurements of hydraulic head can be combined to increase the spatial and temporal density of hydraulic head measurements in the confined aquifer system. We found that at three well locations where the changes in hydraulic head were sufficiently large and the aquifer sediments were relatively compressible the InSAR deformation measurements can be reliably used to estimate hydraulic head during times when no well measurements were acquired.

Keywords: Geophysics.
Advisor: Knight Rosemary (Rosemary Jane)
Zebker Howard A. advisor. Thesis advisor
Zoback Mark D. advisor. Thesis advisor