InSAR imaging of seasonal groundwater change in the San Luis Valley, Colorado
Abstract
The San Luis Valley (SLV) is an 8000 km2 region in southern Colorado that is home to a thriving agricultural economy. The valley is currently in a period of extreme drought, with county and state regulators facing the challenge of developing appropriate management policies for both surface water and ground water supplies. Legislation passed in 2004 requires that hydraulic head levels within 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 confined aquifer system. Interferometric synthetic aperture radar (InSAR) data provide spatially dense maps of deformation of Earth's surface, with one pixel representing the deformation of a 50 m by 50 m area on the ground. This deformation can be related to hydraulic head change in the confined aquifer system. The ability to map these changes, over time, in the SLV will provide critical information about the groundwater system. In this study we used data from the European Space Agency's ERS-1 and ERS-2 satellites, which have 31 acquisitions archived from 1992 - 2001. We applied small baseline subset (SBAS) analysis to create a time series of deformation for all pixels with high data quality. We find that the seasonal deformation measured by InSAR mimics hydraulic head measurements made in the confined aquifer system. We also find that the deformation occurring in the confined aquifer system is primarily elastic and recoverable in nature. At many well locations there are gaps in the hydraulic head record during the period relevant for the 2004 legislation. We find that high quality InSAR data exist during those time periods and can be used to fill historical gaps in hydraulic head data. We have processed the deformation time series for 2500 km2 of area on the ground at a spatial resolution of ~ 50 m. We find it useful to visualize the deformation over such a large area throughout time using an animation depicting the time series deformation patterns. InSAR can be used in this way, as a qualitative tool to see how the extent of groundwater pumping and/or the compressibility of sediments vary throughout the valley. The animation also allows us to identify InSAR acquisitions that show strong atmospheric signals, which were not removed during SBAS analysis.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMNS13A..08R
- Keywords:
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- 1829 HYDROLOGY / Groundwater hydrology;
- 1855 HYDROLOGY / Remote sensing