Researchers from Stanford University have used satellite data and a new computer algorithm to gauge groundwater levels in Colorado’s San Luis Valley agricultural basin. The technique "fills in" underground water levels in areas where quality data had been previously unavailable.
The algorithm supports the creation of better models of groundwater flow, specifically in regions with aquifer depletion.
InSAR satellites use electromagnetic waves to monitor tiny, centimeter-scale changes in the elevation of Earth’s surface. The program, initially developed in the 1980s by NASA, collects data on volcanoes, earthquakes, and landslides. Stanford's researchers, however, adapted the technology for groundwater monitoring.
The scientists, led by former postdoctoral scholar Jessica Reeves, had previously shown that changes in surface elevation could be correlated with fluctuations in groundwater levels. The new algorithm, developed by Jingyi “Ann” Chen, a Stanford postdoctoral researcher, automates the previously time-consuming pixel selection process.
“What we’ve demonstrated in this new study is a methodology that allows us to find high-quality InSAR pixels in many more locations throughout the San Luis Valley,” said Chen.
Chen’s algorithm fills in, or interpolates, groundwater levels in the spaces between pixels where high-quality InSAR data are not available, because of crop coverage or obscuring surface features.
As a result, the team was able to calculate surface deformations – and, by extension, groundwater levels – for the entire agricultural basin of the San Luis Valley, an area covering about 4,000 square kilometers – or about five times greater than the area for which groundwater levels were calculated in the prior study. The team members were able to show how groundwater levels in the basin changed over time from 2007 to 2011.
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