Saturday, December 8, 2012

263 Rivers on Land and 1 River in the Air!

Rivers are the oldest source of freshwater for humans, most ecosystems and most living species.
River Basins
A river basin is the land area from where water drains to feed rivers. The 263 river basins of significant rivers are fed by 45.3% of the land surface area of Earth. The 26 major river basins are shown in the graphic.
26 Largest river basins on Earth
Cartographer - Delphine Digout, UNEP/GRID-Arendal
Arid Areas
The most arid areas are those that do not have enough water i.e. are areas that are not in river basins: Southern California in The US, Western and Central Australia, The Mediterranean sections of Europe, North Africa and others are the  most arid areas on Earth.
The Missing but Largest River of all
Rainfed Agricuture
Source - fao.org
When land areas that serve as river basins are compared with those where rainfed agriculture is predominant, it becomes apparent that much of the water fed into rivers is water delivered by rain.
In a manner of visualization, rain too can be seen as a river in the air or atmosphere.
As is to be expected, the river in the air differs from the rivers that are on the surface of land:
- The river in the air is mobile and is subject to the movements of air streams (that carry the water in this river) in the atmosphere. Land based rivers are, over short periods of time, fixed in space.
- The river in the air is the original river of fresh water that feeds a land-based rivers.
100% of the water in rivers on land is in liquid for, while only 2% of the water in the river in the air is in liquid form. 98% of the water in the air exists as water vapor.

It is this river in the air, that we must find a way to tap when we seek to extract water in the air we breathe.

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