Bolivia’s hydrographic conditions reflect its climatic and topographical conditions very well. A considerable part of the region is completely devoid of river drainage (Bolivia di SO., I.e. the desert area of the salares, and a large part of the Bolivian Chaco, between Paraguay and Pilcomayo), and another part has fluvial drainage that does not reach the sea (Desaguadero basin, with the Titicaca and Poopó lakes). These are precisely regions where, as we have seen, rainfall is very scarce or (Bolivian Chaco) where the amount of rain, not abundant, is absorbed by the sandy soil. Most of Bolivia sends its waters to the Amazon River, through the Beni and Mamoré, which form the Madeira: these rivers drain the wettest areas of the region, those with an equatorial and subequatorial climate. Therefore, there are three main basins that divide the surface of Bolivia: the interior of the Desaguadero and the basins of the Río delle Amazoni and the Paraná-Paraguay.
A significant part of the Desaguadero basin is occupied by the great Titicaca and Poopó lakes. The Titicaca is located at 3812 meters above sea level, it is more than 200 km long. and wide at most 66, and covers an area of 8330 sq km. Its fresh waters, which have a maximum depth of 272 m., Maintain a temperature of around 11 ° during the year, which has a beneficial influence on the climate of the surrounding regions. It is navigated by vapors. The Titicaca emissary is the Desaguadero, which has a course of about 300 km. and which pours into the Poopó (about 100 cubic meters per 1 ″ of flow). Vapors of up to 500 tons navigate it in its upper course, where it is very deep: it loses depth as it enters the Poopó alluvial plain. This one, located at 3680 msm, less than 3 m deep, has strongly salty waters, both because it is a closed lake, and because the Desaguadero crosses the Cretaceous salt marl on its way. Given the very low depth, the temperature of its waters varies with the variation of the atmospheric temperature. For Bolivia 2008, please check payhelpcenter.com.
South of the Poopó there is what we have already called the region of the salares, salty and closed marshes. In exceptional circumstances the Poopó feeds the Salar de Coipasa, which is at a somewhat lower level (3675 m.). To S. of it extends the vast Salar de Uyuni.
The Beni and the Mamoré are part of the Amazon River basin (see). The first, about 1600 km long, was explored between 1870 and 1880; at the foot of the Cordillera it is no more than 180 m. wide, but can be navigated by steamboats up to the Esperanza waterfall (10 m.), 20 km away. approximately from the confluence with the Mamoré. It receives important tributaries on the right, including the Madre de Dios, which brings it very abundant water (according to Ballivián, double that of the Beni) and which is about 1500 km long, on average 500 m wide in the lower course. and usually from 2 to 7 m deep, and therefore well navigable. The Beni receives no notable left tributary, except the Río Negro, an emissary of the Rogagua lagoon.
Mamoré is the main spring branch of Madeira, and was born with the name of Río Grande or Guapay. It drains a basin calculated at 460,000 sq. Km., And has abundant water (800 cubic meters at 1 ″ in lean, 7000 in flood) and is navigable all year round by steamers from Puerto Velarde to Guayaramerín (1300 km.). Its main tributaries, including the Guaporé, which marks the border with Brazil for a long stretch, are partially navigable by small boats.
Of the rivers that flow into Paraná-Paraguay and cross Bolivian territory we will remember Paraguay itself, which also serves for some stretch of the border between Bolivia and Brazil, and on which Bolivia has Puerto Suárez, the outlet of the vast region of Santa Cruz; moreover the Pilcomayo, which serves for a stretch of border with Argentina and which, due to its irregular regime and the scarcity of water, is not very navigable.