Cambodia has a land area of 181,035
square kilometers in the southwestern
part of the Indochina peninsula, about
20 percent of which is used for
agriculture. It lies completely within
the tropics with its southern most
points slightly more than 10° above the
Equator. The country capital city is Phnom Penh.
International borders are shared with Thailand
and the Lao People’s Democratic Republic on
the West and
the North, and the
Social Republic of Viet Nam on the East
and the Southeast. The country is
bounded on the Southeast by the Gulf of
Thailand. In comparison with neighbors,
Cambodia is a geographical contact
country administratively composed of 20
provinces, three of which have
relatively short maritime boundaries, 2
municipalities, 172 districts, and 1,547
communes.
The country has a coastline of 435 km and
extensive mangrove stands, some of which are
relatively undisturbed. The dominant features
of the Cambodian landscape are the large,
almost generally located, Tonle Sap (Great
Lake) and the Bassac River Systems and the
Mekong River, which crosses the country from
North to South. Surrounding the Central Plains
which covered three quarters
of the country’s area are the more densely
forested and sparsely populated highlands,
comprising: the Elephant Mountains and
Cardamom Mountain of the southwest and western
regions; the Dangrek Mountains of the North
adjoining of the Korat Plateau of Thailand;
and Rattanakiri Plateau and Chhlong highlands
on the east merging with the Central Highlands
of Viet Nam.The Tonle Sap Basin-Mekong
Lowlands region consists mainly of plains with
elevations generally of less than 100 meters.
As the elevation increases, the terrain becomes more rolling
and dissected. The Cardamom
Mountains in the southwest rise to more than
1,500 meters and is oriented generally in a
northwest-southeast direction. The highest
mountain in Cambodia –Phnom Aural, at
1.771meters – is in the eastern part of this
range. The Elephant Range, an extension of
Cardamom Mountains, runs towards the south and
the southeast and rises to elevations of
between 500 and 1,000 meters. These two range
are bordered on the west are narrow coastal
plain facing the gulf of Thailand that
contains Kampong Som Bay. The Dangrek
Mountains at the northern rim of Tonle Sap
Basin, consisting of a steep escarpment on the
southern edge of the Korat Plateau in
Thailand, marks the boundary between Thailand
and Cambodia. The average elevation of about
500 meters with the highest points reaching
more than 700 meters. Between the northern
part of the Cardamom ranges and the western
part of the Dangrek, lies and extension of the
Tonle Sap Basin that merges into the plains in
Thailand,
Allowing easy accesses from the border of
Bangkok.The Mekong River Cambodia’s
largest river, dominates the hydrology
of the country. The river originates in
mainland China, flows through Myanmar,
Laos, Thailand before entering Cambodia.
At Phnom Penh, with alternative arms,
the Bassak River from the south, and the
Tonle Sap River linking with the " Great
Lake " itself –Tonle Sap – form
northwest. It continues further
southeastward to its lower delta in Viet
Nam and to the South China Sea.The
section of Mekong River
passing through Cambodia lies within the
topical wet and dry zone. It has a
pronounced dry season during the
Northern Hemisphere winter, with about
80 percent of the annual rainfall
occurring during the southwest monsoon
in May-October
The Mekong River
average annual flow at Kratié of 441 km3 is
estimated as 93 percent of the total Mekong
run-off discharge into the sea. The discharge
at Kratié ranges from a minimum of 1,250m3/s
to the maximum 66,700m3/s.The role of Tonle
Sap as a buffer of the Mekong River system
floods and the source of beneficial dry season
flows warrants explanation. The Mekong River
swells with waters during the monsoon reaching
a flood discharge of 40,000m3/s at Phnom Penh.
By about mid-June, the flow of Mekong and the
Bassak River fed by monsoon rains increases to
a point where its outlets through the delta
cannot handle the enormous volume of water,
flooding extensive adjacent floodplains for
4-7 months.
At this point, instead of overflowing its
backs, its floodwaters reserve the flow of the
Tonle Sap River (about 120 km in length),
which then has the maximum inflow rate of
1.8m/s and enters the Grate Lake, the largest
natural lake in Southeast Asia, increasing the
size of the lake from about 2,600 km2 to 10,00
km2 and exceptionally to 13,000 km2 and
raising the water level by and average 7m at
the height of the flooding. This specificity
of the Tonle Sap makes it the only "river with
return " in the world. After the
Mekong’s water crest (when its downstream
channels can handle the volume of water), the
flow reverses and water flows out of the
engorged lake. The Great Lake then acts as a
natural flood retention basin.
When the floods subside, water starts flowing out of the
Great Lake, reaching a maximum outflow rate of
2.0m/s and, over the dry season, increase
mainstream flows by about 16 percent, thus
helping to reduce salinity intrusion in the
lower Mekong Delta in Viet Nam. By the time
the lake water level drops to its minimum
surface size, a band 20-30 km wide of inundate
forest is left dry with deposits of a new
layer of sediment. This forest, which is of
great significance for fish, is now greatly
reduced in size through salvation and
deforestation. The area flood around Phnom
Penh and down to the Vietnamese border is
about 7,000
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