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Venezuela Hydrography
The Orinoco is by far the most important of the more
than
1,000 rivers in the country. Flowing more than 2,500
kilometers
to the Atlantic from its source in the Guiana highlands at
the
Brazilian border, the Orinoco is the world's eighth
largest river
and the largest in South America after the Amazon. Its
flow
varies substantially by season, with the high water level
in
August exceeding by as much as thirteen meters the low
levels of
March and April. During low water periods, the river
experiences
high and low tides for more than 100 kilometers upstream
from
Ciudad Guayana.
For most of the Orinoco's course, the gradient is
slight.
Downstream from its headwaters, it splits into two;
one-third of
its flow passes through the Brazo Casiquiare (Casiquiare
Channel)
into a tributary of the Amazon, and the remainder passes
into the
main Orinoco channel. This passageway allows vessels with
shallow
drafts to navigate from the lower Orinoco to the Amazon
River
system after unloading and reloading on either side of two
falls
on the Orinoco along the Colombian border.
Most of the rivers rising in the northern mountains
flow
southeastward to the Río Apure, a tributary of the
Orinoco. From
its headwater, the Apure crosses the llanos in a generally
eastward direction. Few rivers flow into it from the
poorly
drained region south of the river and much of this area
near the
Colombian border is swampland.
The other major Venezuelan river is the fast-flowing
Caroní,
which originates in the Guiana highlands and flows
northward into
the Orinoco upstream from Ciudad Guyana. The Caroní is
capable of
producing as much hydroelectric power as any river in
Latin
America and has contributed significantly to the nation's
electric power production
(see Electricity
, ch. 3).
Electricity
generated by the Caroní was one of the factors encouraging
industrialization of the northern part of the Guiana
highlands
and the lower Orinoco valley.
The Lago de Maracaibo, the largest lake in Latin
America,
occupies the central 13,500 square kilometers of the
Maracaibo
lowlands. The low swampy shores of the lake and areas
beneath the
lake itself hold most of Venezuela's rich petroleum
deposits. The
lake is shallow, with an average depth of ten meters, and
separated from the Caribbean by a series of islands and
sandbars.
In 1955 a 7.5-meter channel was cut through the sandbars
to
facilitate shipping between the lake and the Caribbean.
The
channel also allows salt water to mix with the yellowish
fresh
water of the lake, making the northern parts brackish and
unsuited for drinking or irrigation.
Data as of December 1990
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