- Original Caption Released with Image:
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Not all floods are unwanted. Heavy rainfall in southern Africa between
December 2003 and April 2004 provided central Zambia with floodwaters
needed to support the diverse uses of water within the Kafue Flats area.
The Kafue Flats are home to about one million people and provide a rich
inland fishery, habitat for an array of unique wildlife, and the means for
hydroelectricity production. The Flats falls between two dams: Upstream to
the west (not visible here) is the Izhi-tezhi, and downstream (middle right
of the images) is the Kafue Gorge dam. Since the construction of these
dams, the flooded area has been reduced and the timing and intensity of the
inundation has changed. During June 2004 an agreement was made with the
hydroelectricity company to restore water releases from the dams according
to a more natural flooding regime. These images from NASA's Multi-angle
Imaging SpectroRadiometer (MISR) illustrate surface changes to the wetlands
and other surfaces in central Zambia resulting from an unusually lengthy
wet season. The Kafue Flats appear relatively dry on July 19, 2003 (upper
images), with the Kafue River visible as a slender dark line that snakes
from east to west on its way to join the Zambezi (visible in the lower
right-hand corner). On July 21, 2004 (lower images), well into the dry
season, much of the 6,500-square kilometer area of the Kafue Flats remains
inundated. To the east of the Kafue Flats is Lusaka, the Zambian capital,
visible as a pale area in the middle right of the picture, north of the
river. In the upper portions of these images is the prominent roundish
shape of the Lukanga Swamp, another important wetland.
The images along the left are natural-color views from MISR's nadir camera,
and the images along the right are angular composites in which red band
data from MISR's 46° forward, nadir, and 46° backward viewing cameras is
displayed as red, green and blue, respectively. In order to preserve
brightness variations among the various cameras, the data from each camera
were processed identically. Here, color changes indicate surface texture,
and are influenced by terrain, vegetation structure, soil type and soil
moisture content. Wet surfaces or areas with standing water appear blue in
this display because sun glitter makes smooth, wet surfaces look brighter
at the backward camera's view angle. Mostly the landscape appears somewhat
purple, indicating that most of the surfaces scatter sunlight in both
backward and forward directions. Areas that appear with a slight greenish
hue can indicate sparce vegetation, since the nadir camera is more likely
to sight the gaps between the trees or shrubs, and since vegetation is
darker (in the red band) than the underlying soil surface. Areas which
preferentially exhibit a red or pink hue correspond with wetland
vegetation. The plateau of the Kafue National Park, to the west of Lukanga
Swamp, appears brighter in 2004 compared with 2003, which indicates weaker
absorption at the red band. Overall, the 2004 image exhibits a subtle blue
hue (preference for forward-scattering) compared with 2003, which indicates
overall surface changes that may be a result of enhanced surface wetness.
The Multiangle Imaging SpectroRadiometer observes the daylit Earth
continuously and every 9 days views the entire globe between 82° north and
82° south latitude. These data products were generated from a portion of the
imagery acquired during Terra orbits 19072 and 24421. The panels cover an
area of 235 kilometers x 239 kilometers, and utilize data from blocks 100
to 103 within World Reference System-2 path 172.
MISR was built and is managed by NASA's Jet Propulsion Laboratory,
Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra
satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD.
JPL is a division of the California Institute of Technology.
- Image Credit:
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NASA/GSFC/LaRC/JPL, MISR Team.
Image Addition Date:
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2004-11-10
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