Featured Research

from universities, journals, and other organizations

Satellites Measure Bulging Earth To Map Water Resources

Date:
July 2, 2001
Source:
American Geophysical Union
Summary:
Just as a sponge expands when absorbing water, so too does the Earth bulge slightly where aquifers, underground areas of permeable materials, absorb unusually large amounts of water from stream runoff or heavy rains. Scientists using satellite data have been able to measure these bulges on the land surface and believe they can use the technique to study the location and size of aquifers in remote regions.

WASHINGTON - Just as a sponge expands when absorbing water, so too does the Earth bulge slightly where aquifers, underground areas of permeable materials, absorb unusually large amounts of water from stream runoff or heavy rains. Scientists using satellite data have been able to measure these bulges on the land surface and believe they can use the technique to study the location and size of aquifers in remote regions.

Related Articles


Writing in the 1 July issue of Geophysical Research Letters, published by the American Geophysical Union, Zhong Lu and Wesley R. Danskin of the U.S. Geological Survey describe their interferometric analysis of imagery from the synthetic aperture radar (SAR) instruments aboard the European Space Agency satellites, ERS-1 and ERS-2. This technique, known as InSAR, produces an image, called an interferogram, showing differences in land features between two SAR images taken at different times. Synthetic aperture radar is essentially a high resolution radar.

Using the well documented San Bernardino ground-water basin of southern California for their test case, Lu and Danskin detected an uplift of more than seven centimeters [three inches] during the first half of 1993. This period was marked by unusually high runoff from surrounding mountains and high levels of water in nearby wells.

The use of InSAR techniques, supplemented by other remote sensing techniques, to define the extent of an aquifer system simplifies the traditional process, which relies on expensive, ground-based data collection. Traditionally, scientists have had to study a large number of wells to define the boundaries of an aquifer system and its internal structure. By using InSAR to resolve vertical distances to centimeters [inches], and by comparing images taken at different times to detect expansion or subsidence of Earth's surface, they can detect changes in an underlying aquifer.

The San Bernardino area is semi-arid, and ground-water levels rise dramatically in response to recharge from intermittently flowing streams that originate in the San Bernardino and San Gabriel Mountains, which are composed mainly of granite and absorb little water. The area lies between the San Andreas and San Jacinto earthquake fault lines. From 1950 to 1970, groundwater levels in one area fell by about 50 meters [160 feet] and the land subsided by as much as 30 centimeters [12 inches]. From then until 1980, natural and artificial recharge brought water levels in that area to within a meter [three feet] of the surface.

With these and other available data, Lu and Danskin compared 13 InSAR images taken between 1992 and 1995 and produced a series of interferograms. They observed that the seven centimeter [three inch] uplift occurred between December 1992 and August 1993, with four centimeters [two inches] occurring in only three and a half months during the period of greatest runoff. Although significant land subsidence as a result of ground-water pumpage is a well known scientific phenomenon, the magnitude of the observed uplift caused by recharge was unexpected.

The researchers were concerned that the observed land deformation might have been caused by movement of tectonic plates deep below the land surface or by earthquakes, rather than by recharging of the aquifer. They concluded, however, that this was not the case, based on the interferometric patterns acquired from the satellites.

The study was funded by the U.S. Geological Survey and the San Bernardino Valley Municipal Water District.


Story Source:

The above story is based on materials provided by American Geophysical Union. Note: Materials may be edited for content and length.


Cite This Page:

American Geophysical Union. "Satellites Measure Bulging Earth To Map Water Resources." ScienceDaily. ScienceDaily, 2 July 2001. <www.sciencedaily.com/releases/2001/06/010619073415.htm>.
American Geophysical Union. (2001, July 2). Satellites Measure Bulging Earth To Map Water Resources. ScienceDaily. Retrieved March 29, 2015 from www.sciencedaily.com/releases/2001/06/010619073415.htm
American Geophysical Union. "Satellites Measure Bulging Earth To Map Water Resources." ScienceDaily. www.sciencedaily.com/releases/2001/06/010619073415.htm (accessed March 29, 2015).

Share This


More From ScienceDaily



More Earth & Climate News

Sunday, March 29, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

New Arthropod Fossil Might Be Relative Of Spiders, Scorpions

New Arthropod Fossil Might Be Relative Of Spiders, Scorpions

Newsy (Mar. 29, 2015) A 508-million-year-old arthropod that swam in the Cambrian seas is thought to share a common ancestor with spiders and scorpions. Video provided by Newsy
Powered by NewsLook.com
Vietnam Rice Boom Piles Pressure on Farmers and the Environment

Vietnam Rice Boom Piles Pressure on Farmers and the Environment

AFP (Mar. 29, 2015) Vietnam&apos;s drive to become the world&apos;s leading rice exporter is pushing farmers in the fertile Mekong Delta to the brink, say experts, with mounting costs to the environment. Duration: 02:35 Video provided by AFP
Powered by NewsLook.com
Raw: New Eruptions at Colima Volcano in Mexico

Raw: New Eruptions at Colima Volcano in Mexico

AP (Mar. 28, 2015) The Colima Volcano in western Mexico sent large columns of ash up into the air on Saturday. (March 28) Video provided by AP
Powered by NewsLook.com
Antarctic Ice Is Melting Faster Than Ever

Antarctic Ice Is Melting Faster Than Ever

Newsy (Mar. 27, 2015) A new study of nearly two decades of satellite data shows Antarctic ice shelves are losing more mass faster every year. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins