Checking agricultural water levels from space

Stanford University researchers to water regulators: measure water underground from satellites high above.

Watching crop circles from space, geophysicists suggest, might help manage scarce water sources. By crop circles, I mean crops cultivated in neat, irrigated circles.

Researchers from Stanford University discussed at an American Geophysical Union meeting Monday how gauging groundwater levels via InSAR satellites (interferometric synthetic aperture radar) could complement or substitute for data taken from aquifer wells. The satellites measure land movements over time (often giving important data after earthquakes). As water levels in aquifers rise and fall, the shape of the ground changes as well.

The satellites can pick up on these changes in deserts and other barren lands, but not as well for farmland. The constantly growing vegetation essentially hides the ground's elevation changes from the spying eyes miles above. But the geophysicists found that between the lush circles of irrigated land of Colorado's San Luis Valley, the satellites can still accurately measure the dry, plant-free land the sprinklers can't reach.

There isn't a lot of water in the West. But there is a lot of war over it. Water rights are divvied up between agriculture, industry, municipalities, even nature and fish get a share. Wells drilled into aquifers help assess the water availability to avoid drought, but the researchers say there aren't enough wells to always get the best picture.

By comparing InSAR data, Google Earth images and aquifer well measurements, they found the satellite data of the arid pieces of farmland was a good indicator of water levels below the surface. According to the researchers, using InSAR information could be cheaper and provide more data points than drilling more wells.

In a statement, a doctoral student working on the project, Jessica Reeves, says:

Groundwater regulators are working with very little data and they are trying to manage these huge water systems based on that...I think it really has potential to change the way we collect data to manage our groundwater.

Images: Doug Wilson/USDA Agricultural Research Service and InSAR data from Jessica Reeves

This post was originally published on Smartplanet.com