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Country
Background |
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Geography |
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Cambodia
has a land area of 181,035 square
kilometers in the southwestern part of the
Indochina peninsula, about 20% of which is
used for agriculture. It lies completely
within the tropics with its southernmost
points slightly more than 10o
above the Equator.
The
country's capital city is Phnom Penh.
International borders are shared with
Thailand and the Lao People's Democratic
Republic on the west and on the north, and
the Socialist Republic of Vietnam on the
east and the southeast. |
The
country is bounded on the southwest by the Gulf of
Thailand. In comparison with its neighbors,
Cambodia is a geographically compact country
administratively composed of 20 provinces, three
of which have relatively short maritime
boundaries, 3 municipalities, 172 districts, 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
centrally 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 Mountains of the
southwest and western regions; the Dangrek
Mountains of the north adjoining the Korat
Plateau of Thailand; and the Ratanakiri 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
1,771 meters - is in the eastern part of this
range.
The
Elephant Range, an extension of the Cardamom
Mountains, runs toward the south and the
southeast and rises to elevations of between 500
and 1,000 meters.These two ranges are bordered on
the west by a narrow coastal plain facing the Gulf
of Thailand that contains Kampong Som Bay.
The Dangrek Mountains at the northern rim
of the 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 an
extension of the Tonle Sap Basin that
merges into the plains in Thailand, allowing easy
access from the border to 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 its alternative arms, the Bassac
River from the south, and the Tonle Sap
River linking with the "Great
Lake" itself - Tonle Sap - from the
northwest, it continues further southeastward to
its lower delta in Vietnam and to the South China
Sea. The section of Mekong River passing
through Cambodia lies within the tropical wet and
dry zone. It has a pronounced dry season during
the northern hemisphere winter, with about 80% of
the annual rainfall occurring during the southwest
monsoon in May-October. The Mekong River's
average annual flow at Kratie of 441 km3
is estimated as 93% of the total Mekong
run-off discharge into the sea.
The
discharge at Kratie ranges from a minimum
of 1,250 m3 / s to a maximum 66,700 m3
/s. The role of the 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 season reaching a flood
discharge of 40,000 m3 /s at Phnom
Penh. By about mid-June, the flow of the Mekong
and the Bassac Rivers 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 banks, its
floodwaters reverse the flow of the Tonle Sap
River (about 120 km in length), which then has
a maximum inflow rate of 1.8 /s and enters the
Great Lake, the largest natural lake in Southeast
Asia, increasing the size of the lake from about
2,600 km2 to 10,000 km2, at
times exceptionally to 13,000 km2, and
raising the water level by an average 7m at the
height of the flooding. This specifity of the Tonle
Sap River makes it the only "river with
return" in the world. After the Mekong's
waters crest, 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
2.0 m /s and, over the dry season, increase
mainstream flows by about 16%, thus helping to
reduce salinity intrusion in the lower Mekong
Delta in Vietnam. By the time the lake water
level drops to its minimum surface size, a band
20-30 km wide of inundated 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 siltation and
deforestation. The area flooded around Phnom Penh
and down to the Vietnamese border is about 7,000
km2. |
