Click on image for larger annotated version
This image shows pivot irrigation near the city of As Sulayyil (Sulayel),
Saudi Arabia. The edge of the Rub' al-Khali or Empty Quarter is visible in
the southeast.
Modern drilling, pumping, and distribution systems have permitted many
arid and semiarid regions of the world to become productive farmlands. The
circular features that dot the desert landscape are created by pivoting
sprinklers, a method of irrigation whereby water from a central well is
spread by a sprinkler pivoting around that well. Center-pivot irrigation
is most often used in arid and semiarid regions of the world. The diameter
of these circular fields can vary from several hundred feet to over a
mile. Dark circles represent fields where crops are presently grown; faint
circles outline field patterns where no crops are being grown. Some fields
have been taken out of production to lie fallow, some have been harvested
or planted with a new crop, and some have been taken out of production
indefinitely. The water is being extracted from subsurface reserves that
infiltrated deep aquifers during geological periods when the climate was
much wetter than at present. Center-pivot irrigation is not unique to
Saudi Arabia, and there is danger in that there is a finite supply of
"fossil" water for irrigation use.
The Rub' al-Khali is a vast desert in the southern Arabian Peninsula,
covering about 250,000 square miles in a structural basin lying mainly in
southeastern Saudi Arabia, with lesser portions in Yemen, Oman, and the
United Arab Emirates. It is the largest area of continuous sand in the
world. It occupies more than one-quarter of Saudi Arabia. The topography
is varied. In the west the elevation is as high as 2,000 feet and the sand
is fine and soft, while in the east the elevation drops to 600 feet with
sand dunes, salt flats, and sand sheets. One of the driest regions in the
world, it is virtually uninhabited and largely unexplored.
Photojournal note:
EarthKam was formerly known as KidSat. To see images of KidSat, see
http://photojournal.jpl.nasa.gov/mission/KidSat .
