passage: Amazon basin -- The Amazon River rises in the Andes Mountains at the west of the basin with its main tributary the Marañón River in Peru. It is usually considered to be the second longest river in the world. However, a team of Brazilian scientists has claimed that the Amazon is the longest river in the world. It covers about 6,400 km before draining into the Atlantic Ocean. The Amazon and its tributaries form the largest volume of water. The Amazon accounts for about 20% of the total water carried to the oceans by rivers. Some of the Amazon rainforests are deforested because of the increasing of cattle ranches and soy beans field.