A flying river? How the Amazon Forest produces the largest flying river in the world
The Amazon Rainforest is worldwide known for its extraordinary biodiversity and large rivers. The facts speak for themselves. It is the largest tropical forest in the world, covering five million and a half square kilometers in nine countries, including Brazil, which presents 60% of the forest cover. It presents the highest biodiversity among all tropical forests in the world. One in ten known species in the world lives in the Amazon Rainforest. The Amazon basin is also the largest drainage basin in the world. The water flowing through the Amazonian rivers is equivalent to 20% of the Earth's liquid fresh water.
However, what most people don´t know is that the Amazon Rainforest also produces a flying river. Actually, most people can´t even imagine a flying river. It just makes no sense!
Concept of flying river
Flying rivers are 'atmospheric waterways,' made up of masses of air filled with water vapor, often accompanied by clouds, and propelled by the winds. These invisible air currents cross the sky carrying moisture from the Amazon Basin to the Midwest, Southeast, and South of Brazil.
This humidity, in the favorable weather conditions like a cold front coming from the south of South America, for example, turns into rain. It is this action of transporting enormous quantities of water vapor by the air currents that is called flying rivers - a term that perfectly describes in poetic terms a real phenomenon that has a significant impact on the lives of those living in South America.
The Amazon rainforest works like a water pump. It pulls into the continent the moisture evaporated by the Atlantic Ocean and carried by the ally winds. As it moves inland, the humidity drops like rain back on the forest. The trees under the tropical sun suffer evapotranspiration and the forest returns rainwater to the atmosphere in the form of water vapor. This way, the air is always renewed with more humidity, which continues being transported towards the west (Pacific Ocean) to fall again as rain later.
As I said, the flying river runs towards the Pacific Ocean. So all that fresh water should end up in the sea with no use for humans, right? No.
A river that does not end up in the sea
The flying river produced in the Amazon region doesn’t end up in the sea, like normal rivers do, only because of a natural barrier formed by the Andes. When the flying rivers propelled toward the west meet the Andes it partially precipitates on the eastern slopes of the mountain range, forming the headwaters of the Amazonian rivers. However, barred by the 4km-High Mountain, the flying rivers that still carry water vapor, make the curve and start heading south towards the regions of the Midwest, Southeast and South of Brazil and the neighboring countries.
Because of the Andes, large areas of Brazil, Argentina and Paraguay are supplied with a rainfall regime that is so important to the lives, agriculture and energy of those living in these countries.
A river in danger
The replacement of forests by agriculture or pasture are related to significant changes in the South American climate. Scientists predict that clearing the Amazon forest for logging and agriculture is likely to result in lower rainfall regime in other regions. Without the flying river, much of southern Brazil would be an arid desert. Thus, the agribusiness advancement into the Amazon forest can result in a negative impact for agribusiness with the eventual loss of rain that is essential to the agriculture.
The Brazilian law has a series of environmental regulations aimed at reducing deforestation and restoring forests in several biomes in the country. Some exemples are: Environmental assessments (Avaliação de Impacto Ambiental) and degraded areas restoration plans (Plano de Recuperação de Áreas Degradadas - PRAD). However, unfortunately government inspection in the Amazon region are quite often inefficient due to several reasons.