Environmental Science & Engineering - www.esemag.com - September 2002
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Satellites can peer underground to monitor
aquifer levels
Satellite data will soon enable
researchers to measure changes
in groundwater levels. The
new technique, using National
Aeronautics and Space Administration
(NASA) satellites, may prove vital for
the management of water resources for
agriculture, other human water needs
and wildlife. Many of the world's aquifer
levels are now monitored with
ground-based wells, a labour and equipment
intensive approach that offers incomplete
coverage.
The replenishment of underground
aquifers – groundwater recharge – is also
difficult to monitor using the groundbased
approach. With the satellite information,
all large underground water
sources can be measured with reasonable
accuracy, providing important data
that can help address worldwide water
shortages, and perhaps locate new aquifers.
University of California at Irvine
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) to monitor
groundwater.
The GRACE mission, launched in
March 2002, will map variations in the
Earth's gravity field. These gravitational
variations 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 later this
year.
Famiglietti and Rodell are the only
hydrologists to work on the GRACE
project. They have developed a mathematical
model to isolate groundwater
information from overall water storage
data. 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. "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."
Famiglietti noted 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.
Any new and objective method for
monitoring the availability of water resources
will be valuable for assessing
future development and sustainability."
For more information on GRACE:
www.csr.utexas.edu/grace/ or essp.gsfc.nasa.gov/grace/
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