Brazil, having an abundant rainfall, extensive forests of valuable timber, and large areas of fertile soil. The mountain slopes are still masses of dense forest, though their lower elevations and neighbouring valleys have been cleared for cultivation and by dealers in rosewood and other valuable woods. This elevated valley is noted for its fertility and was once the principal coffee-producing district of Brazil.
Outside the two great river systems of the Amazon and river Plate (Rio de la Plata), which are treated under their respective titles, the rivers of Brazil are limited to the numerous small streams and three or four large rivers which flow eastward from the plateau regions directly into the Atlantic. The Rivers. Amazon system covers the entire north-western part of the republic, the state of Amazonas, nearly the whole of Pará and the greater part of Matto Grosso being drained by this great river and its tributaries. If the Tocantins-Araguaya basin is included in the hydrographic system, the greater part of Goyaz and a small part of Maranhão should be added to this drainage area. The Tocantins is sometimes treated as a tributary of the Amazon because its outlet, called the Rio Pará, is connected with that great river by a number of inland channels. It is an entirely separate river, however, and the inland communication between them is due to the slight elevation of the intervening country above their ordinary levels and to the enormous volume of water brought down by the Amazon, especially in the flood season. As the outlet of the Tocantins is so near to that of the Amazon, and their lower valleys are conterminous, it is convenient to treat them as parts of the same hydrographic basin.
In the extreme north-east corner of the republic where the Brazilian Guiana plateau slopes toward the Atlantic there is a small area lying outside the drainage basin of the Amazon. Its rivers flow easterly into the Atlantic and drain a triangular-shaped area of the plateau lying between the northern frontier and the southern and western watersheds of the Araguary, whose extreme limits are about 0° 30′ N. lat. and 53° 50′ W. long. The more important of these rivers are the Araguary, Amapá, Calçoene, Cassiporé and Oyapok. The Araguary rises in the Tumuc-Humac mountains, in about 2° 30′ N. lat., 52° 10′ W. long., and follows a tortuous course south and north-east to the Atlantic. Its largest tributary, the Amapary, rises still farther west. Little is known of the country through which it flows, and its channel is broken by rapids and waterfalls where it descends to the coastal plain. The Amapá is a short river rising on the eastern slopes of the same range and flowing across a low, wooded plain, filled with lagoons. The Calçoene and Cassiporé enter the Atlantic farther north and have a north-east course across the same plain. All these small rivers are described as auriferous and have attracted attention for this reason. The Oyapok, or Vicente Pinzon, is the best-known of the group and forms the boundary line between Brazil and French Guiana under the arbitration award of 1900. It rises in about 2° 05′ N., 53° 48′ W., and flows easterly and north-easterly to the Atlantic. Its course is less tortuous than that of the Araguary.
The rivers of the great Brazilian plateau which flow directly to the Atlantic coast may be divided into two classes: those of its northward slope which flow in a northerly and north-easterly direction to the north-east coast of the republic, and those which drain its eastern slope and flow to the sea in an easterly direction. The former reach the coastal plain over long and gradual descents, and are navigable for considerable distances. The latter descend from the plateau much nearer the coast, and are in most cases navigable for short distances only. In both classes navigation is greatly impeded by sandbars at the mouths of these rivers, while in the districts of periodical rainfall it is greatly restricted in the dry season. The more important rivers of the first division, which are described in more detail under the titles of the Brazilian states through which they flow, are the following: the Gurupy, Tury-assú, Mearim, Itapicurú and Balsas, in the state of Maranhão; the Parnahyba and its tributaries in Piauhy; Jaguaribe in Ceará; and the Apody and Piranhas in Rio Grande do Norte. Of these the Parnahyba is the most important, having a total length of about 900 m., broken at intervals by rapids and navigable in sections. It receives only one important tributary from Maranhão—the Rio das Balsas, 447 m. long—and five from Piauhy, the Urussuhy-assú, Gurgueia, Canindé, Poty and Longa. Piauhy is wholly within its drainage basin, although the river forms the boundary line between that state and Maranhão throughout its entire length. All the rivers in this division are influenced by the periodical character of the rainfall, their navigable channels being greatly shortened in the dry season (August-January). In Ceará the smaller rivers become dry channels in the dry season, and in protracted droughts the larger ones disappear also.
The rivers of the second division are included in a very great extension of coast and are influenced by wide differences in climate. Their character is also determined by the distance of the Serra do Mar from the coast, the more southern rivers having short precipitous courses. The more northern rivers are subject to periodical variations in volume caused by wet and dry seasons, but the greater distance of the coast range and the more gradual breaking down of the plateau toward the sea, give them longer courses and a greater extent of navigable water. North of the São Francisco the watershed projecting from the plateau eastward toward Cape St Roque, known as the Serra da Borborema in Parahyba and Rio Grande do Norte where its direction becomes north-east, leaves a triangular section of the easterly slope in which the river courses are short and much broken by rapids. The rainfall, also, is limited and uncertain. The largest of this group of small rivers is the Parahyba do Norte, belonging to the state of Parahyba, whose length is said to be less than 200 m., only 5 or 6 m. of which are navigable for small steamers. The São Francisco, which belongs to the inland plateau region, is the largest river of the eastern coast of Brazil and exists by virtue of climatic conditions wholly different from those of the coast where it enters the Atlantic. The tributaries of the lower half of this great river, which belong to the Atlantic coast region, are small and often dry, but the upper river where the rainfall is heavier and more regular receives several large affluents. The river is navigable up to the Paulo Affonso falls, 192 m. from the coast, and above the falls there is a much longer stretch of navigable water.
From the São Francisco to Cape Frio there are many short rivers rising on the slopes of the plateau and crossing the narrow coastal plain to the sea. There are also a few of greater length which rise far back on the plateau itself and flow down to the plain through deeply cut, precipitous courses. The navigable channels of these rivers are restricted to the coastal plain, except where a river has excavated for itself a valley back into the plateau. The more important of these rivers are the Itapicurú, Paraguassú, Contas or Jussiape, Pardo or Patype, and Jequitinhonha, of Bahia; the Mucury, and Doce, of Espirito Santo; and the Parahyba do Sul of the state of Rio de Janeiro. Of the Bahia group, the Jequitinhonha, sometimes called the Belmonte on its lower course, is the longest and most important, rising near Serro in the state of Minas Geraes and flowing in a curving north-east direction for a distance of about 500 m., 84 of which are navigable inland from the sea. The Mucury and Doce also rise in Minas Geraes, and are much broken in their descent to the lower plains, the former having a navigable channel of 98 m. and the latter of 138 m. The Parahyba, or Parahyba do Sul, which enters the sea about 30 m. north of Cape S. Thomé, is the largest and most important of the Atlantic coast rivers south of the São Francisco. It rises on an elevated tableland in the state of São Paulo and flows across the state of Rio de Janeiro from west to east, through a broad fertile valley producing coffee in its most elevated districts and sugar on its alluvial bottom-lands nearer the sea. It has a total length of 658 m., 57 of which are navigable between S. Fidelis and its mouth, and about 90 m. of its upper course.
South of Cape Frio there are no large rivers along the coast because of the proximity of the Serra do Mar—the coastal plain being very narrow and in places disappearing altogether. There are many short streams along this coast, fed by heavy rainfalls, but they have no geographic importance and no economic value under existing conditions. The largest of these and the only one of commercial value is the Ribeira de Iguape, which has its source on the tablelands of Paraná and after receiving several affluents west of the Serra do Mar breaks through a depression in that range and discharges into the Atlantic some miles below Santos on the southern boundary of the state of São Paulo. This river has a navigable channel of 118 m. below Xiririca, and communicates with an inland canal or waterway extending for many miles along this coast and known as the Iguape, or Mar Pequeno. In Rio Grande do Sul the Atlantic coastal plain extends westward more than half-way across the state, and is well watered by numerous streams flowing eastward to the Lagôa dos Patos. Of these only two are of large size—the Guayba and Camaquam. The first is formed by the confluence of the Jacuhy, Cahy, Sinos and Gravatahy, and is known under this name only from Porto Alegre to the Ponta de Itapuã, where it enters the Lagôa dos Patos. This river system drains a large part of the northern mountainous region of the state, and has a considerable extension of navigable channels between the plateau margin and the lake. In the extreme southern part of the state, the Lagôa Mirim empties into the Lagôa dos Patos through a navigable channel 6112 m. long, called the Rio São Gonçalo.
The Brazilian rivers of the Rio de la Plata system are numerous and important. Those of the Paraguay drain the south-western part of Matto Grosso, and the tributaries of the Paraná cover the western slopes of the Serra do Mar from Rio Grande do Sul north to the south-west part of Minas Geraes, and include the south-east part of Matto Grosso and the south part of Goyaz within their drainage basin. This is one of the most important fluvial systems of Brazil, but its economic value is impaired by the great waterfalls of Guayrá, or Sete Quedas, and Uribú-punga, and by the rapids and waterfalls in the majority of its affluents near their junction with the main stream. Between the two great waterfalls of the Paraná there is an open channel of 276 m., passing through a rich and healthy country, and receiving large tributaries from one of the most fertile regions of Brazil. Among the larger of these are the great falls of the Iguassú, near the junction of that river with the Paraná. Though the Uruguay plays a less important part, its relations to the country are similar to those of the Paraná, and its tributaries from the plateau region are similarly broken by falls and rapids. The Paraguay is in great part a lowland river, with a sluggish current, and is navigable by large river steamers up to Corumbá, and by smaller steamers to Cuyabá and the mouth of the Jaurú.
