Rivers. – According to TOPPHARMACYSCHOOLS, Paraguay is a predominantly low and largely flat country, but it has a very varied morphology and its landscape is anything but monotonous. In the area between the Paraná and Paraguay rivers rise the last offshoots of the red sandstone plateau of the Matto Grosso; they push east towards the Paraná with gentle undulations, but, where the diabases replace the sandstones, the tributaries of the Paraná have carved deep and rocky valleys. Towards the west, the plateau ends with an escarpment, the edge of which has the name of Sierra (Sierra de Amam. Bay, de Maracajú); to the north this hem has the asymmetrical profile of a typical cuesta and is fronted by low hills. At the center of the village it reaches up to 680 m. a red sandstone massif surmounted by diabase, which erosion has completely separated from the Altipiano del Matto Grosso. Between this massif and the aforementioned Sierras, in northern Paraguay, there is a penepiano of granite and gneiss covered by a thick layer of decaying soil, slightly undulating and 200 meters high; it is dominated to the west by a massive strait of syenites, porphyries, micascists and quartzites, bordered by faults, a horst (Sierra de las Quince Puntas), which towards the west and south is faced by limestone hills. The low plains that surround. to the West and to the East. towards Paraná and Paraguay, the highest areas, where they form flat and swampy plains, where hilly or only undulating areas.
A large uniform low plain is the Chaco, inclined from NW, where it is also 300 m high, towards SE, where it drops to 80 m. Near the Paraguay river its uniformity is interrupted by low dunes (see chaco).
Hydrography. – Hydrographically the whole country is part of the Río de la Plata basin, because, as mentioned, it is crossed by Paraguay and limited to the east by Paraná, both completely navigable within the borders of the republic; the former receives various notable tributaries in Paraguayan territory, such as the Ipané, the Jejuy and the Tebicuary, which are also partly navigable. Frequent are the lagunas and esteros (permanent swamps invaded by vegetation).
Weather Conditions. – The climate, which does not present very strong differences between one part of the country and another; it is hot and humid. Annual temperature excursions are usually large; rainfall falls at any time of the year, but it is mainly in summer (35%) and spring (31%) and decreases as it proceeds towards the W and NW. The capital, Asunción, located at 25 ° 17 ‘of lat. S. and just over 100 m. above sea level, it has an average annual temperature of 22 °, 9, with 17 ° in the coldest month (June) and 26 °, 9 in the hottest month (January); rainfall amounts to 1315 mm annually, with a maximum in December (154 mm.) and a minimum in August (38 mm.). Villarrica, which is further east of Asunción, has 1800 mm. of rains. In Chaco the rains are usually less than 1000 mm. The predominant winds are those of the I and II quadrant.
Flora and vegetation. – Given the position of the territory, the flora is subtropical and therefore presents intermediate characters between tropical and temperate. In Paraguay, from the phytogeographical point of view, two regions can be distinguished: the eastern and the western. In the first dominate the woods, consisting of large trees with numerous lianas and species showy and showy flowers, interrupted occasionally by high covered grasslands and dense herbaceous vegetation and hills with groves of palms (Cocos australis, C. Sclerocarpa) . There are also orange groves always loaded with fruit, groups of plane trees and the Enterolobium timbouva which in spring is covered with a wreath of purple flowers. The second region, which includes the Chaco, is made up of a bare and vast plain scattered here and there by Cocos yatais which sometimes come together to form groves; where the ground rises, there are vast woods of quebracho to interrupt the monotony of the landscape. Only in the easternmost part of the territory is there the yerba mate or Paraguayan tea (Ilex paraguariensis). Among the plants that provide building timbers you can remember: Prosopis dulcis, Aspidosperma Quebracho, Pyptadenia communis, Acacia cavenia, A. maleolens, Tecoma curialis, T. It varies, T. leucoxylon, Hectandra porphyria, Cedrela brasiliensis, Araucaria brasiliensis, Vitex Taruma. Among the fruit plants: Psidium microcarpum, Hancornia speciosa, Genipa americana, Anona sylvatica. Other useful plants live: coca, Copernicia cerifera which provides the vegetable wax, Hymenaea courbaril from which a kind of copal is obtained, Croton succirubrum which produces a sort of dragon’s blood, the Bombax ventricosa in the fruits of which a vegetable silk is contained. In the tropical forests there are numerous epiphytic orchids, which in the country are called, due to their epiphytism, “flowers of the air”. The families most richly represented in the Paraguayan flora are: Leguminosae, Anacardiaceae, Cucurbitaceae, Euphorbiacee, Rutaceae, Mirtaceae, Begoniacee, Urticaceae.
Fauna. – Very rich and interesting, like the neotropic one in general. Various monkeys inhabit the forests of the region. Chiroptera are also represented by absolutely characteristic neotropic species, including vampires. Insectivores are missing. Carnivores are numerous and among them the ozelot, the undi, the eyra among the Felids, the maned dog, the carasissi among the Dogs; the red-nosed nasua among the Raccoons. Among the Ungulates the llama, the labiate peccary, the tapir. Among the Rosicanti there are many species of guinea pigs including the aperea, some porcupines, some squirrels and mice. Among the Toothless the armadillo, the tatù, the peba, the anteater, the tamandua. Paraguayan avifauna are very rich in forms and the reptiles with numerous species of saurians and ophidî are very noteworthy. Similarly interesting are the species of anuran amphibians and freshwater fish. Characteristic are the entomofauna and the terrestrial malacofauna, in which there are large species.