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Paraguay Drainage
Rivers have greatly influenced the character of the country. The
R�o Paraguay and R�o Paran� and their tributaries define most of
the country's borders, provide all its drainage, and serve as
transportation routes. Most of the larger towns of the interior, as
well as Asunci�n, are river ports.
The R�o Paraguay has a total course of 2,600 kilometers, 2,300
of which are navigable and 1,200 of which either border on or pass
through Paraguay. The head of navigation is located in Brazil, and
during most years vessels with twenty-one-meter drafts can reach
Concepci�n without difficulty. Medium-sized ocean vessels can
sometimes reach Asunci�n, but the twisting course and shifting
sandbars can make this transit difficult. Although sluggish and
shallow, the river sometimes overflows its low banks, forming
temporary swamps and flooding villages. River islands, meander
scars, and oxbow (U-shaped) lakes attest to frequent changes in
course.
The major tributaries entering the R�o Paraguay from the
Parane�a region--such as the R�o Apa, R�o Aquidab�n, and R�o
Tebicuary--descend rapidly from their sources in the Paran� Plateau
to the lower lands; there they broaden and become sluggish as they
meander westward. After heavy rains these rivers sometimes inundate
nearby lowlands.
About 4,700 kilometers long, the R�o Paran� is the second major
river in the country. From Salto del Guair�, where the river enters
Paraguay, the R�o Paran� flows 800 kilometers to its juncture with
the R�o Paraguay and then continues southward to the R�o de la
Plata Estuary at Buenos Aires, Argentina. In general, the R�o
Paran� is navigable by large ships only up to Encarnaci�n but
smaller boats may go somewhat farther. In summer months the river
is deep enough to permit vessels with drafts of up to three meters
to reach Salto del Guair�, but seasonal and other occasional
conditions severely limit the river's navigational value. On the
upper course, sudden floods may raise the water level by as much as
five meters in twenty-four hours; west of Encarnaci�n, however, the
rocks of the riverbed sometimes come within one meter of the
surface during winter and effectively sever communication between
the upper river and Buenos Aires.
The rivers flowing eastward across the Parane�a region as
tributaries of the R�o Paran� are shorter, faster-flowing, and
narrower than the tributaries of the R�o Paraguay. Sixteen of these
rivers and numerous smaller streams enter the R�o Paran� above
Encarnaci�n.
Paraguay's third largest river, the R�o Pilcomayo, flows into
the R�o Paraguay near Asunci�n after demarcating the entire border
between the Chaco region and Argentina. During most of its course,
the river is sluggish and marshy, although small craft can navigate
its lower reaches. When the R�o Pilcomayo overflows its low banks,
it feeds the Estero Pati�o.
Drainage in the Chaco region is generally poor because of the
flatness of the land and the small number of important streams. In
many parts of the region, the water table is only a meter beneath
the surface of the ground, and there are numerous small ponds and
seasonal marshes. As a consequence of the poor drainage, most of
the water is too salty for drinking or irrigation.
Because of the seasonal overflow of the numerous westwardflowing streams, the lowland areas of the Parane�a region also
experience poor drainage conditions, particularly in the �eembuc�
Plain in the southwest, where an almost impervious clay subsurface
prevents the absorption of excess surface water into the aquifer.
About 30 percent of the Parane�a region is flooded from time to
time, creating extensive areas of seasonal marshlands. Permanent
bogs are found only near the largest geographic depressions,
however.
Data as of December 1988
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