What’s a flying river?

Reading about high elevation winds and the jet stream recently, I came across a term that I was not familiar with – “flying rivers”. Many of us learned about the water cycle back in school and I wrote a Wise About Water post about it back in 2016. Today, that water cycle cycle has been expanded and refined to include all aspects of water movement. The processes remain the same, but the complexities – groundwater recharge, water withdrawal, permafrost – are now a little more clearly understood. Flying rivers fall into the category of small scale water cycles.

Brazilian scientist Antonio Nobre first used the term ‘flying river’ 20 years ago as he tried to understand why there were no deserts in South America. He found that without the Amazon rainforests, much of South America would be a desert. Every large tree in the Amazonian jungle releases 1000 liters of water into the atmosphere in a single day. The Amazon River itself moves 17 billion tons of water to the sea each day, but Nobre found that it is still smaller than what is moving through the air. Together, the trees release more than 20 billion metric tons of water daily! This massive solar powered sprinkler system, as Nobre calls it, would be impossible for humans to replicate and it is critical to protect it. (See the resources below for a link to Nobre’s 2015 TED talk about the Amazon’s flying river.)

Trees Do So Much More Than Photosynthesize!

Trees forming clouds above a forest. Image: Marek Bukovan on Unsplash.com.Flying rivers are found all across the world. A review paper published in 2017 – Trees, forests, and water: cool insights for a hot world (Ellison et al.) shares the following about trees, water cycles, and precipitation:
– On average, at least 40% of rain falling on land starts with evapotranspiration by trees and plants in forests.
– Precipitation recycling, rarely considered in public policy and discussion, is key to understanding water in downwind locations.
– Forests are a major influence on cloud formation.
– The biotic pump theory suggests that large continuous areas of forests engaging in evapotransporation maintain and drive the atmospheric circulation patterns that bring rainfall to the interior of continents.
– Forests cool locally and globally. A single large tree transpires the equivalent cooling power of two average household air conditioning units per day!

A man holding his arms around the trunk of a big tree. Image: Angela Shambaugh

This large white cedar lives in a wetland along the Clyde River in the NEK.

The world around us is intricate, interconnected in ways that we may never fully understand. Your lake depends in part on water flowing into it from rainfall generated by trees. Change is constant and inevitable -forests will grow and fall as part of the natural cycle. Yet in Vermont, the size of our forests is shrinking (see the VT Digger story in the resources list below). So, don’t take trees for granted! Think carefully before you cut and make it a point to plant new trees every year. Hug a tree today!

Dig Deeper With These Resources: