Re: Why do most rivers flow North to South?

The idea that most rivers flow North to South is one that is often expressed, especially by 
Americans.

It is simply not true that "most rivers" flow North to South.

Let us do a quick survey of the world's large rivers. No river flows in a single direction, but they all 
do have a general trend.

The Amazon flows West to East
The Nile flows South to North
The Mississippi Flows North to South

In Africa,
the Congo flows East to West

In Asia
the Yeinsei flows South to North
the Amur-Ussuri, Yangtze, Hwang Ho, Pearl River, and Ganges flow West to East
the Mekong flows North to South

In Europe
The Danube flows West to East
The Rhein flows East to West

In Australia
The Murray flows East to West
the Darling flows North to South

In South America all of the major rivers flow West to East 

The direction a river flows in depends simply on where the mountain ranges are, and on where the 
rainfall occurs.

In South America, for example (the most spectacular example, and easiest to understand), there is 
a very high range of mountains, the Andes, running North-South along the Western edge of the 
continent. In the Northern part of South America, the tropical winds blow from the East, and 
deposit the rain on the Eastern side of the range. There is a long flow across relatively flat country 
for this rain to accumulate into rivers and reach the ocean. In Colombia and Ecuador, there is some 
rain on the Western side, but any rivers that form are short and relatively insignificant, because the 
range is close to the coast. Further South in Peru and Northern Chile, the Western side of the 
Andes is a desert. Yet further South, the Westerly airstream makes Southern Chile one of the 
wettest climates on Earth, but it is only a few kilometres from the range to the coast, so the rivers 
that do form there hardly look noticeable on the world map. So all of the major rivers in South 
America have their headwaters on the Eastern side of the Andes, and flow from West to East to 
reach the ocean.