Use of NASA Technology Seen as Breakthrough to Understanding Water Availability and Movement
Irvine, Calif., June 10, 2002 -- By using data from NASA satellites, a UC Irvine researcher will be able to measure changes in underground aquifer water levels, which may prove vital for water resource management in key areas such as agriculture and human water needs.
The use of these satellites is seen as a major breakthrough for studying the underground storage levels and water replenishment changes in large aquifer systems throughout the world. Currently, many of the world's aquifer levels are monitored with ground-based wells, a labor- and equipment-intensive approach with often incomplete coverage. In addition, aquifer replenishing, which is called groundwater recharge, is exceedingly difficult to monitor using the ground-based approach.
With the satellite information, potentially all large underground water sources can be measured with reasonable accuracy, providing important data that can help address the worldwide water crisis. Plus, new aquifers also may be found.
UCI hydrologist James Famiglietti and Matthew Rodell of NASA's Goddard Space Flight Center will be using data from NASA's Gravity Recovery and Climate Experiment (GRACE). The GRACE mission, launched in March 2002, will accurately map variations in the Earth's gravity field. These gravitational variations will come from measurements of changes in the distribution of the Earth's mass, which includes all water storage sources, such as oceans, lakes, rivers, ice, soil water and aquifers. Initial GRACE data will be available during the summer. Famiglietti and Rodell are the only hydrologists to work on the GRACE project.
While prior studies have determined that GRACE is capable of evaluating surface and groundwater changes, Famiglietti and Rodell have developed a mathematical model to isolate groundwater information from overall water storage data. To test this method, the researchers studied changes in groundwater levels in the High Plains aquifer, which is located under seven states in the central United States and is the major source of water for irrigation in the region. Their findings appear in the June 10 issue of the Journal of Hydrology.
"It has been nearly impossible in the past to accurately measure the changes in underground water storage," said Famiglietti, an associate professor of Earth system science and of civil and environmental engineering at UCI. "GRACE presents a breakthrough not only as a means to measure these changes but provides researchers with a way to understand how and why these changes take place, which has significant implications for water resources management."
The U.S. Geological Survey has assessed water level changes in the High Plains aquifer for decades, relying on data from more than 6,200 monitoring wells scattered across the region. Using data collected between 1987 and 1998, Famiglietti and Rodell derived estimates based upon their GRACE model. They have concluded that annual groundwater changes in the High Plains aquifer will be estimated to within about 8.7 millimeters of actual amounts by using GRACE observations of the Earth's gravity field. Famiglietti notes, however, that it will not be possible to measure the absolute mass of groundwater storage, only the changes in mass either from year to year or season to season.
"The prospect of satellite-based monitoring of groundwater is intriguing because most other satellites only monitor Earth's surface. GRACE provides us with an exciting opportunity to remotely observe processes beneath the surface and to construct a simultaneous, global view of changes in water storage," Famiglietti said. "Many regions of the world are experiencing a water crisis that is better attributed to management policies than to scarcity of water. Therefore, any new and objective method for monitoring the availability of water resources will be valuable for assessing future development and sustainability."
Famiglietti and Rodell also plan to use GRACE information to produce monthly estimates of water storage changes for several of the world's large watershed and groundwater systems. Additionally, they plan to refine their methods of estimating groundwater recharge and to develop new methods to estimate evaporation and the volume of snowmelt. The potential exists, Famiglietti adds, to study how water availability and groundwater storage respond to global warming.
NASA funded the research. For more information on GRACE, click
here and here.
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