(Website editor: I have included this excerpt because it describes in some detail the situation with the Paraná-Paraguay river system in the middle of the 19th century and before modern development.)
The Argentine Confederation contains also an extensive tract of hilly country which lies between the rivers Paraná and Uruguay. In the northern part of this region is the Laguna de Ybera, which extends from north to south in some places nearly 100 miles, and noweher else less than 40 miles; and from east to west about 80 miles. It covers an area of more than 3000 square miles. A narrow strip of elevated ground divides its northern border from the Rio Paraná, and it is supposed that it is supplied with water from that river by infiltration, as no stream enters it; and it supplies with water four small rivers, one of which, the Mirinay, runs to the Uruguay, and the three others to the Paraná. The surface of this low tract however is only a deep swamp, interspersed with numerous small lakes. It is chiefly covered by aquatic plants and shrubs, but in most parts it is impassable. The country extending southward from this lake to the confluence of the Paraná with the Uruguay has an undulating surface, the heights seldom rising into hills, except in the interior and at a few places along the Paraná. It is chiefly overgrown with trees between which there are some savannas of moderate extent. On the plains numerous herds of cattle are pastured, which constitute the wealth of the country. Though the trees are of stunted growth, the entire want of forests in the surrounding countries makes this wood of great demand for the ordinary purposes of cabinet-work, for carriages, and as timber for small houses. The interior of the country appears to be much more hilly than along the rivers, and is occupied by the forest of Monteil, which extends more than 100 miles from north to south, with an average width of 40 miles. It is encumbered with brushwood and studded with small trees. At the southern extremity of the country, along the banks of the Paraná, there is a low tract, which is subject to occasional inundations. That portion of this country which extends from the lake of Ybera in north-eastern direction to the boundary-line of Brazil is known under the name of the Missiones, from the circumstance, of the Jesuits having collected here a great number of aborigines, and accustomed them to a civilised life. The establishments are now in ruins, and the population dispersed. The south-western part, which is undulating, has a soil of great fertility, producing cotton, sugar and other tropical productions. To the north-east of it the country rises into high hills and mountains, which are covered with tall timber-trees, the most southern of which occur east of the Andes from the Strait of Magalhaens.
Hydrography, Communications etc. - All the rivers which drain the Argentine Confederation, as far as it is situated north of 34°S. lat. carry their waters to the wide estuary called La Plata. Before they reach this fresh-water sea, they form two large rivers, the Paraná and the Uruguay, which with their affluents are not only admirably adapted to render available all the resources of the Argentine Provinces, affording an unbroken channel of communication for some thousands of miles, but would open a ready means for adventurous traders to penetrate into the heart of the mineral districts of Bolivia, Brazil and Peru. Along the banks of these rivers there can be little doubt that when the country becomes totally freed from anarchy, and its inhabitants turn to the peaceful pursuit of commerce, the population will concentrate and numerous busy towns will arise. The Paraná originates hardly twenty miles from the shores of the Atlantic, on the table-land of Brazil. After leaving that country at its confluence with the river Iguazú, the Paraná continues to run between the Argentine Confederation and Paraguay, in a southern direction for about 50 miles, when it turns gradually to the south-west, and continues in that direction to the large island of Apipé, a distance of about 100 miles. This part of the river is not navigable in all its extent, as there are several rapids and small falls, the last in the neighbourhood of the island of Apipé. This large island, with whose dimensions we are not acquainted, is the point where the uninterrupted navigation of the Paraná begins and where large quantities of timber are shipped, the river being navigable for vessels of 300 tons burden. From Apipé the river runs westward nearly 100 miles, when it is joined by the Rio Paraguay from the north, and at the point of confluence it suddenly turns to the west of south. Below the junction with the Paraguay, the width of the river varies from one mile and a half to two miles, but the whole volume of water seldom flows in one channel, as the current is divided by a continuous series of islands overgrown with low trees, and subject to inundations. The islands, which are of various sizes, are in a constant state of decay and renovation; new ones are continually being formed whenever any obstruction occurs, and old ones constantly being destroyed. These islands and the numerous sand-banks render the navigation slow and tedious. At Santa Fé the river begins to divide into various branches, and to run southward. After a course of about 100 miles it turns to the south-east at Rosario, and thence to its mouth in La Plata the number of its branches increases. It opens into La Plata with a large number of embouchures, forming a long, but comparatively narrow delta, composed of a great number of islands. The most northern branches fall into the wide mouth of the Rio Uruguay. Its principal outlet is that which is called Paraná Guazú (the Great Paraná) in which there is seldom less than two fathoms and a half of water. The mouth called Paraná de las Palmas is the deepest, next to the Guazú. The Paraná runs nearly 900 miles within the boundary of the republic, of which 750 miles are navigable for vessels of 300 tons all the year round. In the summer the river is raised somewhat above its natural level, owing to the melting of the snows, but towards the end of the year, intertropical rains having filled the upper branches, it begins to rise, and continues to do so for four months, to the end of April. The average rise below its junction with the Paraguay is stated to be 12 feet. It then inundates the adjacent grounds, particularly below Santa Fé, and the tracts which are thus laid under water are said to cover a surface of 4000 square miles, an estimate which is perhaps overrated. The water leaves behind a gray slimy deposit, which is very favourable to vegetation. At the end of April the water begins to fall, and the fall is somewhat more rapid than the rise. The Paraná, as has been said, is navigable for vessels of considerable burden as far as Corrientes, but the strength of the current renders the navigation very tedious for sailing vessels. Its capability for steam vessels was sufficiently proved during the blockade of La Plata by the British and French squadron, when H.M steamer Alecto, of 200 horse power, and 800 tons burden, ascended the river to Corrientes and back, nearly 2000 miles, in 39 days. This voyage strikingly illustrated the vast superiority of steam for the navigation of this river; for the Alecto actually overtook and passed on her way to Corrientes a fleet of sailing vessels, which left Monte Video while the Alecto was fitting at Woolwich. These vessels took 112 days to reach Corrientes from Monte Video. Captain Sullivan, R.N made a very careful survey of the river during the blockade, and the Board of Admiralty has caused a beautiful series of Charts of the Paraná to be engraved and published from his drawings. According to Captain Sullivan, "when the river is high vessels drawing 16 feet of water may ascend as high as San Juan, in 30° 36´ S. lat., and those drawing 12 feet may go up to Corrientes, with two feet to spare; but when the Paraná is at its lowest, vessels attempting to ascend it should not draw more than 6 feet." By a decree of Urquiza, as Provisional Director of the Argentine Confederation, dated August 31, 1852, the navigation of the Plata, the Paraná and the Uruguay is opened to all foreign vessels under 120 tons burden.
The Paraguay, the largest of the affluents of the Paraná, originates likewise in Brazil. Having passed through the Estrecho de S. Francisco (20° S. lat.), at the Fecho dos Morros, it continues to flow with a gentle current in a southern direction, dividing Paraguay from the Gran Chaco, until, at 25° 30' S. lat., and about 20 miles below Asuncion in Paraguay, the channel is narrowed at a place called Angostura by protruding rocks, between which the current runs with great rapidity. From this point it runs west by south to its junction with the Paraná. Vessels of considerable size may navigate this river within the boundaries of the republic, along which it runs about 400 miles. The channel in these parts being confined between high banks, the water rises 30 feet, but the inundations of the adjacent tracts are not extensive. Its waters are increased by two large tributaries, the Pilcomayo and Rio Vermejo. The Pilcomayo rises in the Andes, in two branches. The southern, called Rio de S. Junan and afterwards Pilaya, originates in the Despoblado; and the northern, the proper Pilcomayo, derives its water from the numerous rivers which descend from the Andes between the Despoblado and the vale of the Desaguadero in Bolivia, and partly also from those which originate in the mountains that inclose that vale. These two rivers receive the drainage of the eastern declivity of the Andes between 19° and 23° S. lat., and unite after a course of about 350 miles, near 20° 40' S. lat., and 62° 50' W. long. After the union of these branches the Pilcomayo is a broad and deep river, and runs about 700 miles to its junction with the Paraguay, first easterly and afterwards to the south-east. In this part of its course it flows with innumerable windings through the Gran Chaco, where it is joined by no large river, and where its waters are gradually absorbed by the arid country through which it runs. Thus it becomes extremely shallow, and neither of the two arms into which it divides 200 miles above its mouth is navigable, even for small boats, to a distance exceeding 100 miles from the Paraguay. These two arms are called Araguay Guazú and Mini. The Vermejo derives its water from the Despoblado, the Abra de Cortaderas, and the table-land of Yavi, descending from which elevated regions it forms two rivers, the Rio de Tarija on the north , and the Rio Lavayen on the south. The first truning southward, joins the second at the eastern base of the table-land of Yavi, and both form the Vermejo, which flows about 700 miles through the Gran Chaco with numerous windings, until it joins the Rio Paraguay nearly 40 miles above it confluence with the Paraná. The Rio Vermejo is navigable for large boats as far as the union of its great branches.
Monday 7th October 2019
Paper on breeding performance of the Lear's Macaw in the wild
I was recently sent a paper on the breeding performance of the Lear's Macaw in the wild. I was interested to read the comparison with other macaw species. The Lear's macaw has been quite prolific in captivity and it appears it is also prolifi ... Read More »
" Naturam expellas furca, tamen usque recurret "
( If you drive out nature with a pitchfork, she will soon find a way back)
Horace (65-8 BC)