The Pilcomayo, the Bermejo and the Salado erode quantities of the Pampean material, dissolve it into silt and pour it into the Paraguay and Parana rivers. The engineer, Pelleschi, estimates that "the soil annually subtracted from the territory of the Chaco by the Bermejo alone equals 6,400,000 cubic yards." Lower Course of the Parana.—From 31° 3o' south to the Plata estuary the western bank of the Parana is a precipitous bluff of reddish clay, varying from 25 to 75ft. above mean river level. It is being gradually undermined, and tumbles into the water in great blocks, adding to the immense volume of silt which the river carries. The Parana is lowest in December; it rises in January, February and March, reaching its greatest height in March. It is steady in April, May and June, but falls and rises irregularly dur ing the next three months. The difference between low and high river is generally about izft., depending upon the varying quan tity of rains in Brazil and the melting of the Andean snows. Below its junction with the Paraguay the Parana has an average current of 21M. an hour, and the river varies in width from 1 to 3m., at low water; but in floods it seems almost a continuous lake, broad ening to 10 and 3om. and burying many of its numerous islands and marginal swamps under a vast sheet of water, and obliterating its many parallel lateral channels and connecting canals.
In the middle Parana, from the mouth of the Iguazu to the mouth of the Paraguay river, there are many islands, some of them large, rocky and high above the river. From Paraguay to the city of Rosario, islands are numerous, many of them of great area; and again below Rosario they soon increase in number and size until the Plata estuary is reached. In flood time the upper portion of the trees being out of water, they have the appearance of floating forests. Then the river often makes wild work with its banks, and builds up or sweeps away entire islands, leaving deep channels instead. The lower delta of the Parana does not share in these phenomena; its islands and main channels appear more fixed. This probably is due to the less eleva tion attained by the waters in flood-time, and the numerous branches which distribute them into the Plata estuary. This must have extended, in a very recent geological period, inland from its present head to at least 32° S. ; but the enormous quantity of silt which the Parana receives from its Paraguay affluent, and from the tributaries which reach it from the Andes, has filled this length of about 220M. with these muddy islands, which rest upon a sandy bed of great depth.
The frontage of the Parana delta is 4om. across, almost in a straight line from north to south. Through this the river finds its way to the Plata by i 1 outlets, large and small, the two principal ones being the Parana-Guaza and the Parana de las Palmas. The Parana is navigable to the Sao Lou renco river by craft drawing 3ft. of water. and to within a few
miles of AsunciOn, the capital of Paraguay. by vessels drawing 9ft. The city of Parana may always he reached with a draught of 12 and Rosario with 15ft. of water.
The commercial development of the Plata basin promises to become gigantic. The Andes on the west, the interior of South America on the north, great rivers, and the Brazilian mountains on the east of the Plata basin are obstacles which compel the rich and varied products of at least 1,500,000sq.m. of fertile country to seek access to the ocean by a single avenue—the Plata estuary.
(G. E. C.) During the 20 years ending in 1928 many of the ports, cities and towns located on the Plata-Parana-Paraguay river system have made marked progress. Millions of dollars have been spent in ex tending and improving shipping facilities by Montevideo, La Plata, Buenos Aires, Rosario—all of them ports of call for ocean-going steamships. Many of the smaller ports like Santa Fe, Parana, Corrientes, Posadas and Asuncion, have also improved their fa cilities, and have increased their exports of grain, hides, meat, quebracho wood and extract, mate and lumber.
The completion, in 1916, of a 37m. railway around the Falls of Guayra, on the Alto Parana river, opened a new river and rail gateway to the heart of Brazil, the principal outward shipments being yerba-mate and dried beef. A new hotel at IguazU River falls and a motor-car service from Puerto Aguirre to the falls, iom. distant, provide modern accom modation, and, aided by better steamboat service on the Alto Parana have brought more tourists to the cataracts. The Rondon, the Roosevelt (1913-14) and other expeditions of recent years; the colonization schemes of European and American companies in Paraguay and Bolivia; the completion of a Brazilian railway from Sao Paulo nearly to the Paraguay; petroleum investigations in eastern Bolivia; larger areas planted with cotton in Argentina and Paraguay have combined to arouse wider interest in the vast region watered by the Plata river system. On the Uruguay river the cities of Mercedes, Paysandu and Salto have new water sys tems, improved streets and extended sanitation. A packing plant at Fray Bentos has increased operations there. The Argentine Navigation company, the Lloyd Brazileiro and local steamboat lines operate La Plata services to Corumba, Brazil, 1,800m. from the Atlantic. Ocean-going vessels ascend as far as Rosario and Santa Fe 200M. and 3oom. above Buenos Aires. Throughout the Plata region the gradual introduction of modern agricultural im plements has increased output, and, consequently, river traffic.
J. Holland, To the River Plate and Back (1913) ; G. Ross, Argentine and Uruguay (1916) ; A. Boerger, Sieben la
(1921) ; Review of the River Plate (Buenos Aires, weekly). (W. A. R.; G. E. C.)