According to findjobdescriptions, the Paraguayan territory occupies the northern section of the great Platense lowland which separates the ancient plateaus of Brazil from Andean South America. The most important geographical element of the country, so much so as to give it its name, is the Río Paraguay, a vital axis both for communications and for its function as a pole of human attraction. It divides the country into two very clear parts, geomorphologically and anthropically: to E the section that is linked to the Brazilian massifs, and which concentrates almost the entire population, to W that which is connected to the Andean foothills, semi-desert. The vital part of the country corresponds to eastern Paraguay, between the course of the Río Paraguay and that of the Río Paraná, vast triangle of lowlands into which the extreme reaches of the Brazilian highlands are pushed; the very ancient crystalline base of the Brazilian shield (Archaeozoic) emerges in some points, but it is generally covered by a thick Paleozoic and Mesozoic sedimentary layer (Triassic sandstones prevail), with Cenozoic basaltic expansions. These mountainous appendages are moved by a rigid style tectonics, with fractures, depressions and horst, while presenting a substantially mature morphology; the ridges have a general trend from N to S (Serra de Amambay, Serra de Maracaju, etc.), the altitudes are never very high and only in some places exceed 500 m (700 m near Villarrica, 880 m near Pedro Juan Caballero). Apart from this mountainous section, eastern Paraguay is flat, with large swampy surfaces along the course of the Paraguay and Paraná rivers, whose periodic flooding is responsible for the formation of extensive amphibious areas (esteros). AW del Río Paraguay the territory extends towards the Andean foothills, thus including a vast section of the Chaco (Chaco Boreal), a large plateau consisting of sedimentary accumulations of a continental character (floods and neozoic aeolian deposits), whose average altitude is everywhere below the 200 m, interrupted only by some isolated hills (Cerro León, 1000 m).
The two physical regions, well defined structurally and morphologically, into which the country is commonly divided, acquire a more precise identification considering the hydrography. The eastern part, enclosed between the Paraguay and Paraná rivers, in fact includes a dense network of navigable waterways, whose considerable flow and steadiness of regime are due to the copious rains, which through the lower course of the Paraná communicate directly with the Atlantic and thus remedy to a large extent the absence in the country of its own outlets to the sea. Paraguay, one of the major South American rivers, descending from Mato Grosso (Brazil) crosses the territory from N to S for a thousand km; it winds in Paraguay with a meandering course, in a bed full of muddy floods, among vast marshy areas; its width varies from 300 to 1000 meters. It receives numerous tributaries including Apa, Jejui-Guazú, Tebicuary from the left, and Mount Lindo and Pilcomayo from the right. Just NE of Corrientes tribute in the Paraná, of which it constitutes the greatest tributary. Paraná, however, is of limited interest to Paraguay, of which it partly marks the southern and eastern borders (Argentina and Brazil); it flows mainly embedded between crystalline rocks and very resistant sandstones, which cuts through a deep bed interrupted by numerous waterfalls including those of Guaíra (or Sete Quedas), near the city of the same name. Near Ciudad del Este, the dam of the Paraná with the construction of the Itaipu dam (the name means in the Tupí language “the rock that sings”) determined at the turn of the seventies and eighties of the century. XX the formation of a large artificial basin. The course of the river becomes calmer and more regular only in the southern part of Paraguay, where it receives the Paraguay (in Encarnación it is already 1500 m wide). In the western section, where the rains are much more scarce, the hydrographic network is, on the other hand, just hinted at: the watercourses head towards the SE following the general slope of the territory and many are even exhausted in the permeable deposits of the lowland, without reaching the sea.. The only important river is the aforementioned Pilcomayo which, moreover, is rather marginal, marking for a long stretch the border between Paraguay and Argentina; born from the Andes, it slowly crosses the Chaco plain, and in the lower areas its bed is lost in vast swampy areas cluttered with vegetation, which hinder navigation.