6
Gerardo M.E. Perillo . M. Cintia Piccolo . Mario Pino-Quivira
ies depicted along the United States, Canada and Western Europe received a very detailed attention provided by local expertise and advanced technology, most of the ones
in the rest of the world have only received elemental attention even though the effort
of local researchers and some international interest.
There is still a much larger number of estuaries that has not received even the most
basic attention. As we are going to describe in the present chapter, this is the case for
most estuaries in South America. As well as it occurs in Central America, Asia and
Africa, the number of estuaries about which we have some knowledge is overwhelmed
by the number of those from which we know barely their names. Therefore, the objective of the present chapter is actually to show the lack of knowledge and the opportunity for research that there is available in South America. Although this concept
is also valid for other estuaries in the world.
1.3
Estuaries of South America
Figure 1.4 provides a general description of the major estuaries present along the South
America coast. As estuaries are dependent of fluvial input, the distribution is also
closely related to the precipitation conditions on the continent as well as the local topography. The Northern and Eastern regions of the continent are part of the Amazonia
with very high levels of precipitation (over 1200 mm yr -I). Therefore, the number of
rivers and lagoons that reach the Atlantic Ocean in this area is very large. There are
also many small rivers that reach the Pacific Ocean in Colombia and Ecuador, but their
length and catchment basins are small because they have their sources in the nearby
Andes mountains.
Similar situation occurs as we move down along the Western coast of South America,
rivers are relatively small when they are formed in near coast mountains like the
Coastal Range in the South of Chile. The larger rivers are those that have sources at
the main Andes range (i.e., Bio Bio and Valdivia Rivers in Chile). However, south of
the Guayas Estuary, the Pacific coast has mean annual precipitation significatively
lower than the Atlantic counterpart down to the Bio Bio River. Thus the number of
rivers and their strength is dramatically reduced and associated to the microtidal
conditions, practically there are no estuaries in this stretch of the coast.
South of the Valdivia River, precipitation rates becomes high again (2000 mm yr-'),
but most of this rain falls along the Coastal Range of southern Chile. Therefore,
there are hundreds of high, torrential type rivers that form small enclosed estuaries,
many of them develop choked coastal lagoons (i.e., Queule, Tubul). Further south
the Chilean coast up to Tierra del Fuego is cut by deep valleys developed by alpine
glaciers that reached its maximum during the last Pleistocene glaciation. Today all
those valleys are fjords from which the most remarkable is the Mercier Channel which
is estimated as the deepest fjord in the world with maximum depths in excess of
1200 m.
The Northern coast of South America presents some of the largest rivers in the
planet, specifically the Amazon, Demerara and Orinoco Rivers which have extensive
basins that cross most of the continent. Although many rivers reach the Atlantic in
Northern Brazil down to the Doce River, most of them have their origin at the Brazilian Shield and have steep basins and short lengths.
Gerardo M.E. Perillo . M. Cintia Piccolo . Mario Pino-Quivira
ies depicted along the United States, Canada and Western Europe received a very detailed attention provided by local expertise and advanced technology, most of the ones
in the rest of the world have only received elemental attention even though the effort
of local researchers and some international interest.
There is still a much larger number of estuaries that has not received even the most
basic attention. As we are going to describe in the present chapter, this is the case for
most estuaries in South America. As well as it occurs in Central America, Asia and
Africa, the number of estuaries about which we have some knowledge is overwhelmed
by the number of those from which we know barely their names. Therefore, the objective of the present chapter is actually to show the lack of knowledge and the opportunity for research that there is available in South America. Although this concept
is also valid for other estuaries in the world.
1.3
Estuaries of South America
Figure 1.4 provides a general description of the major estuaries present along the South
America coast. As estuaries are dependent of fluvial input, the distribution is also
closely related to the precipitation conditions on the continent as well as the local topography. The Northern and Eastern regions of the continent are part of the Amazonia
with very high levels of precipitation (over 1200 mm yr -I). Therefore, the number of
rivers and lagoons that reach the Atlantic Ocean in this area is very large. There are
also many small rivers that reach the Pacific Ocean in Colombia and Ecuador, but their
length and catchment basins are small because they have their sources in the nearby
Andes mountains.
Similar situation occurs as we move down along the Western coast of South America,
rivers are relatively small when they are formed in near coast mountains like the
Coastal Range in the South of Chile. The larger rivers are those that have sources at
the main Andes range (i.e., Bio Bio and Valdivia Rivers in Chile). However, south of
the Guayas Estuary, the Pacific coast has mean annual precipitation significatively
lower than the Atlantic counterpart down to the Bio Bio River. Thus the number of
rivers and their strength is dramatically reduced and associated to the microtidal
conditions, practically there are no estuaries in this stretch of the coast.
South of the Valdivia River, precipitation rates becomes high again (2000 mm yr-'),
but most of this rain falls along the Coastal Range of southern Chile. Therefore,
there are hundreds of high, torrential type rivers that form small enclosed estuaries,
many of them develop choked coastal lagoons (i.e., Queule, Tubul). Further south
the Chilean coast up to Tierra del Fuego is cut by deep valleys developed by alpine
glaciers that reached its maximum during the last Pleistocene glaciation. Today all
those valleys are fjords from which the most remarkable is the Mercier Channel which
is estimated as the deepest fjord in the world with maximum depths in excess of
1200 m.
The Northern coast of South America presents some of the largest rivers in the
planet, specifically the Amazon, Demerara and Orinoco Rivers which have extensive
basins that cross most of the continent. Although many rivers reach the Atlantic in
Northern Brazil down to the Doce River, most of them have their origin at the Brazilian Shield and have steep basins and short lengths.