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Uruguay Topography and Hydrography
Most of Uruguay is a gently rolling plain that
represents a
transition from the almost featureless Argentine pampas to
the
hilly uplands of southern Brazil. The country itself has
flat
plains on its eastern, southern, and western edges. The
narrow
Atlantic coastal plain is sandy and marshy, occasionally
broken
by shallow lagoons. The littorals of the R�o de la Plata
and the
R�o Uruguay are somewhat broader and merge more gradually
into
the hilly interior
(see
fig. 3).
The remaining three-quarters of the country is a
rolling
plateau marked by ranges of low hills that become more
prominent
in the north as they merge into the highlands of southern
Brazil.
Even these hilly areas are remarkably featureless,
however, and
elevations seldom exceed 200 meters.
Uruguay is a water-rich land. Prominent bodies of water
mark
its limits on the east, south, and west, and even most of
the
boundary with Brazil follows small rivers. Lakes and
lagoons are
numerous, and a high water table makes digging wells easy.
Three systems of rivers drain the land: rivers flow
westward
to the R�o Uruguay, eastward to the Atlantic or tidal
lagoons
bordering the ocean, and south to the R�o de la Plata. The
R�o
Uruguay, which forms the border with Argentina, is flanked
by low
banks, and disastrous floods sometimes inundate large
areas. The
longest and most important of the rivers draining westward
is the
R�o Negro, which crosses the entire country from northeast
to
west before emptying into the R�o Uruguay. A dam on the
R�o Negro
at Paso de los Toros has created a reservoir--the Embalse
del R�o
Negro--that is the largest artificial lake in South
America. The
R�o Negro's principal tributary and the country's second
most
important river is the R�o Y�.
The rivers flowing east to the Atlantic are generally
shallower and have more variable flow than the other
rivers. Many
empty into lagoons in the coastal plain. The largest
coastal
lagoon, Laguna Mer�n, forms part of the border with
Brazil. A
half-dozen smaller lagoons, some freshwater and some
brackish,
line the coast farther south.
Data as of December 1990
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