Humanities › Geography Amazon River Basin Countries Share Flipboard Email Print Galen Rowell/Getty Images Geography Basics Physical Geography Political Geography Population Country Information Key Figures & Milestones Maps Urban Geography By Amanda Briney Geography Expert M.A., Geography, California State University - East Bay B.A., English and Geography, California State University - Sacramento Amanda Briney, M.A., is a professional geographer. She holds a Certificate of Advanced Study in Geographic Information Systems (GIS) from California State University. our editorial process Amanda Briney Updated February 17, 2019 The Amazon River is the second longest river (it is just shorter than the Nile River in Egypt) in the world and it has the largest watershed or drainage basin as well as the most tributaries of any river in the world. For reference, a watershed is defined as the area of land that releases its water into a river. This entire area is often referred to as the Amazon Basin. The Amazon River begins with streams in the Andes Mountains in Peru and flows into the Atlantic Ocean about 4,000 miles (6,437 km) away.The Amazon River and its watershed encompass an area of 2,720,000 square miles (7,050,000 sq km). This area includes the largest tropical rainforest in the world - the Amazon Rainforest. In addition parts of the Amazon Basin also include grassland and savannah landscapes. As a result, this area is some of the least developed and most biodiverse in the world. Countries Included in the Amazon River Basin The Amazon River flows through three countries and its basin includes three more. The following is a list of these six countries that are part of the Amazon River region arranged by their area. For reference, their capitals and populations have also been included. Brazil Area: 3,287,612 square miles (8,514,877 sq km)Capital: BrasiliaPopulation: 198,739,269 (July 2010 estimate) Peru Area: 496,225 square miles (1,285,216 sq km)Capital: LimaPopulation: 29,546,963 (July 2010 estimate) Colombia Area: 439,737 square miles (1,138,914 sq km)Capital: BogotaPopulation: 43,677,372 (July 2010 estimate) Bolivia Area: 424,164 square miles (1,098,581 sq km)Capital: La PazPopulation: 9,775,246 (July 2010 estimate) Venezuela Area: 352,144 square miles (912,050 sq km)Capital: CaracasPopulation: 26,814,843 (July 2010 estimate) Ecuador Area: 109,483 square miles (283,561 sq km)Capital: QuitoPopulation: 14,573,101 (July 2010 estimate) Amazon Rain Forest Over half the world rainforest is located in the Amazon Rain Forest which is also called Amazonia. The majority of the Amazon River Basin is within the Amazon Rain Forest. An estimated 16,000 species live in the Amazon. Although the Amazon Rain Forest is huge and is incredibly biodiverse it's soil was not suitable for farming. For years researchers assumed that the forest must have been sparsely populated by humans because the soil could not support the agriculture needed for large populations. However, recent studies have shown the forest was much more densely populated than previously believed. Terra Preta The discovery of a type of soil known a terra preta has been found in the Amazon River Basin. This soil is the product of ancient jungle foresty. The dark soil is actually a fertilizer made from mixing charcoal, manure and bone. The charcoal is primarily what gives the soil its characteristic black color. While this ancient soil can be found in several countries in the Amazon River Basin it's primarily found in Brazil. This isn't surprising as Brazil is the largest country in South America. It's so large it actually touches all but two other countries in South America.