Groundwater and how much we have of it is becoming a greater and greater concern in the United States. Cities that have relied on groundwater for water are seeing depletions in their water resources as the climate changes and as more and more water is pumped out of underground aquifers to service growing cities.
The many factors that influence groundwater levels has been difficult to calculate in the past, but new research from Stanford may bring us closer to understanding the water that lies beneath our feet.
Using An Algorithm to Map Groundwater Levels
A computer algorithm has been developed at Stanford University that allows researchers to determine groundwater levels over large geographical areas using satellite imagery. The algorithm, developed by Jingyi ‘Ann’ Chen, uses imagery provided by the Interferometric Synthetic Aperture Radar (InSAR) to determine groundwater levels. The technique was demonstrated in a research paper written by the Stanford group about the San Luis Valley in Colorado.
Using Electromagnetic Waves to Map Small Changes in the Surface of the Earth
InSAR satellites monitor changes in the elevation of the surface of the Earth on a very small scale using electromagnetic waves. Changes in groundwater levels have been shown to influence surface elevation, but these measurements were difficult to distinguish if cities or agricultural fields were obscuring the satellite picture.
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The Stanford team was able to gather data for more locations using InSAR with the help of the algorithm, which interpolates groundwater levels between available InSAR images.
The team was also able to extract information on the varying factors that influence groundwater levels and the subsequent change in surface elevation; for instance, a sand aquifer will have immediate surface level change when water is pumped out, whereas a clay aquifer will have a time delay from when the water is released to when the surface level sinks.
The Stanford research team hopes to expand the algorithm to other groundwater locations throughout the United States to continue gathering data. They also hope to put this information to good use in improving current groundwater flow models to further gain insight into how much water we have, how much we are using, and what the consequences are.
More:
Chen, J., Knight, R., Zebker, H. A., & Schreüder, W. A. (2016). Confined aquifer head measurements and storage properties in the San Luis Valley, Colorado, from spaceborne InSAR observations. Water Resources Research.
Than, K. (2016, June 8). Stanford researchers calculate groundwater levels from satellite data.
