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Published December 14, 2011 | Published
Journal Article Open

High quality InSAR data linked to seasonal change in hydraulic head for an agricultural area in the San Luis Valley, Colorado

Abstract

In the San Luis Valley (SLV), Colorado legislation passed in 2004 requires that hydraulic head levels in the confined aquifer system stay within the range experienced in the years 1978–2000. While some measurements of hydraulic head exist, greater spatial and temporal sampling would be very valuable in understanding the behavior of the system. Interferometric synthetic aperture radar (InSAR) data provide fine spatial resolution measurements of Earth surface deformation, which can be related to hydraulic head change in the confined aquifer system. However, change in cm-scale crop structure with time leads to signal decorrelation, resulting in low quality data. Here we apply small baseline subset (SBAS) analysis to InSAR data collected from 1992 to 2001. We are able to show high levels of correlation, denoting high quality data, in areas between the center pivot irrigation circles, where the lack of water results in little surface vegetation. At three well locations we see a seasonal variation in the InSAR data that mimics the hydraulic head data. We use measured values of the elastic skeletal storage coefficient to estimate hydraulic head from the InSAR data. In general the magnitude of estimated and measured head agree to within the calculated error. However, the errors are unacceptably large due to both errors in the InSAR data and uncertainty in the measured value of the elastic skeletal storage coefficient. We conclude that InSAR is capturing the seasonal head variation, but that further research is required to obtain accurate hydraulic head estimates from the InSAR deformation measurements.

Additional Information

© 2011 by the American Geophysical Union. Received 7 December 2010; revised 20 September 2011; accepted 19 October 2011; published 14 December 2011. We are grateful to Eric Harmon of HRS Water Consultants Inc. for his assistance with this work. We would like to thank UNAVCO for access for to their WInSAR and Geoearthscope SAR archives. This research was supported primarily by a Nelson award to Jessica Reeves from the Department of Geophysics at Stanford University, with additional support through funding to R. Knight from Schlumberger Water Services.

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August 22, 2023
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