Physical Geography

The Andes, in the west and southwest, make up about a third of Bolivia. This lofty highland region consists primarily of a high plateau, called the Altiplano, and great mountain ranges, called cordilleras. The Altiplano, bleak and windswept, is a series of basins lying more than 12,000 feet (3,660 m) above sea level. The northern part is the home of the Aymará Indians and the site of La Paz, Bolivia's principal city. The south ern section is thinly populated and desertlike, with extensive salt flats.

Flanking the Altiplano are the Cordillera Occidental on the west and the Cordillera Real, Cordillera Central, and Cordillera Oriental on the east. All are largely treeless ranges, crowned by some of the loftiest peaks in the Americas. The highest is snowcapped Sajama, which reaches 21,463 feet (6,542 m) in the Cordillera Occidental near the Chilean border. Slightly lower are Illimani, Illampu, and other peaks in the vicinity of La Paz. Nestled in the eastern ranges are several broad basins containing major cities and good farming areas.

The eastern edge of the Andes divides into two strongly contrasting regions: the Yungas in the north and the Puna in the south. The Yungas region is marked by a sharp decrease in elevation—from high mountains with deep, narrow valleys to luxuriant tropical lowlands—within a short distance. The Puna, less steeply inclined, has long, gentle slopes leading to subtropical lowlands.

The eastern lowlands, often called the Oriente, make up roughly two-thirds of the country. They lie largely within the Amazon Basin but partly within the Gran Chaco region of South America. The lowlands consist primarily of tropical forests and grasslands, some of which are marshy and poorly drained. The region is sparsely settled, but has enormous potential for development.

Lake Titicaca, once the sacred lake of the Incas, is the largest freshwater lake in South America. Situated more than 12,500 feet (3,810 m) above sea level on the Peru-Bolivia border, it is the highest navigable lake in the world. Salty Lake Poopó, fed by Lake Titicaca's overflow water, is the only other large lake.

Nearly all of the major rivers of Bolivia rise in the eastern ranges and flow generally northward, mainly as the headstreams of Amazon River tributaries. They include the Madre de Dios, Beni, Mamoré, Grande, and San Miguel. The Pilcomayo and other rivers flowing toward the southeast are part of the Paraná system.

Although Bolivia lies in the tropics its climate varies from hot to permanently cold, largely because of great differences in elevations. At La Paz, on the edge of the Altiplano at an altitude of nearly 12,000 feet (3,660 m), all months are chilly, with temperatures averaging near 50° F. (10° C.). Temperatures vary more from night to day than from season to season. Summer (December through February) is the rainy period. Cochabamba, which lies on the eastern slope of the Andes at about 8,500 feet (2,590 m), has a similar climate, but temperatures are somewhat higher. The northern part of the eastern lowlands is hot and rainy the year round; the southern part, hot and alternately wet and dry. Annual rainfall ranges from more than 80 inches (2,030 mm) in the Amazon Basin to less than 5 inches (127 mm) in the southern part of the Altiplano.