The Amazon is probably the world's greatest river. Sure, the Nile is slightly longer but the Amazon, for reasons listed below, far outweighs the Nile in importance to both the human population and the entire ecosystem as a whole.
Does size matter?
Well, only if you’re a river I guess. You see, the average
discharge of
water into the
Atlantic Ocean by the Amazon is about 175,000 cubic meters per second. To put that figure in perspective, that’s about between 1/5 and 1/6 of the total discharge into the oceans of all rivers in the world. This discharge is 4-5 times that of the
Congo River, and 10 times that of the
Mississippi River.
Even of the Amazons tributaries, the Rio Negro, can stake the claim of being the second largest river in the world in terms of water discharge, in places its over 300 feet deep and almost 9 miles wide at the mouth of the rive at Manaus Brazil.
So where does all this water come from or , more aptly, raindrops keep falling on my head?
Well, the average rainfall across the whole Amazon basin is about 7 ½ feet per year. In some areas of the northwest basin, rainfall averages a staggering 19.7 feet per year.
Hey, that’s a lot of water, where does it all go?
Actually, of all the water discharged into the Atlantic Ocean by the mighty Amazon, only about 1/3rd of the water that falls into the basin is rain. What happens to the other 2/3? Well, up to half that amount may never reach the ground in the first place, being intercepted by the forest and
evaporated right back into the
atmosphere. Some more evaporation occurs from from the surfaces of the ground and river and
transpiration from the leaves of plants. All of this evaporated moisture re-enters the water cycling system of the Amazon, and a given
molecule of water may be "re-cycled" many times between the time that it is evaporated from the surface of the Atlantic Ocean and carried by the prevailing winds into the Amazon basin, to the time that it is carried back to the ocean by the Amazon River.
The long and winding road
The total length of the Amazon River from its source springs in the
Andes is estimated at 4075 miles. This figure does not take into account all of the bends and twists that the river makes on its journey to the Atlantic. By comparison, the Nile is relatively straight and clock in at about 4145 miles. The headwaters of the Amazon are located in the Andes at an elevation of about 17,000 feet) and are only 120 miles from the
Pacific Ocean
Two peas in a pod
Two of the tributaries of the Amazon are almost identical, both the Juruá and Madeira rivers are both about 2,060 miles long. All in all, about 1,100 other tributaries empty into the Amazon River.
You sure got a pretty mouth
The mouth of the Amazon is about 200 miles wide. It also contains Marajó Island, the worlds largest freshwater island.
How low can you go?
When it leaves the Andes, the
grade of the Amazon is very low. At Iquitos,
Peru, still about 2,250 miles from the Atlantic, the river level at low water season is only about a bit more than 300' above sea level, and the slope is less than one inch vertical change.
Its up! Its Down!
Seasonal water levels can vary up to 65 feet in the middle Amazon region. Towards the mouth of the Amazon, the yearly change becomes less and less, but even near the mouth of the Amazon its still about 12 feet.
This variation in water levels means that huge areas along the major rivers in the Amazon basin are periodically flooded. The total flooded area represents about 4% of the forest area and can extend up to 50 miles from the main river channels.
Just goin’ with the flow
As mentioned earlier, due to the low slope and grade of the Amazon, one would think that it rate of flow would be quite slow. Not so, current speeds range from 0.5-1.0 meters per second at low water, and twice that at flood stage. In localized areas, current speeds can reach as high as 9.8 feet per second.
World's Biggest Outhouse
In the Atlantic Ocean beyond the mouth of the Amazon, and resting on the continental shelf, the sediments (made up mostly of clay and mud, come to rest on the ocean floor and are about 36,000 feet thick.
World's Biggest Washtub
The Amazon basin (the watershed of the Amazon River) is about 2,500,000 square miles, and covers about 40% of
South America. The Amazon basin covers significant portions of the countries of Brazil, Peru,
Colombia,
Ecuador,
Venezuela and
Bolivia The next largest tropical watershed, that of the Congo River, is only half the size of the Amazon basin.
What lives there or bouillabaisse anybody?
The Amazon basin is home to over 2,400 known species of fish.
Believe it or not, that's more species than are found in the entire Atlantic Ocean. Estimates have been made that there might be over 5,000 species. These range from giant air-breathing fish and river
catfish weighing up to 600-700 lbs, to tiny
tetras,
electric eels,
stingrays,
needlefish, fresh-water
flying fish, and knife fish. New species and variations of the aforementioned species are frequently discovered.
Yeah, but it's a dry heat...
Once upon a time, the Amazon basin was not always an area of tropical rainforest. It’s been discovered that at several times during its history, the basin has been home to huge lakes and shallow seas. Salt deposits up to nearly 2000 feet thick have also been found in some locations. This indicates that the basin might have been desert like and when the seas dried up, the salt deposits were left behind.
If it was a desert, where are the dunes?
Sonic measurements of the riverbed below the mouth of the Rio Negro show giant sand dunes 2000 feet in length and up to 39 feet in height. The current of the river gradually moves these “dunes” downstream, much the same way that winds shift the dunes in that of a desert.