Drainage basin research

Rivers Report

João Guilherme B.H.

15/9/15

A drainage basin is an area drained by a main river and its smaller tributaries. The drainage basins are separated by natural boundaries called watersheds.

The main components of a river are the source, tributaries, confluence, main river and mouth.  Usually the land around the river has vegetation even in very different biomes. Studying the Amazon drainage basin some examples are:

Amazon

The water of the river Amazon comes from the snow of the Andes Mountains in Peru. The source of the river amazon has not yet been found for certain but scientists think it is the river Vilcanota in Peru that flows into Brazil as rio Solimões and turns into the Amazon in its confluence with rio Negro. The Amazon drainage basin has many tributaries such as the rio Tapajós, rio Madeira, etc. The Amazon drainage basin is known for being the biggest on earth with about 7 million square kilometers and occupies 40% of the Brazilian geographical area. Around the Amazon River runs the Amazon rainforest.

Upper course of the river:

V shaped valleys are formed by erosion. This land for is formed when erosion happens for millions and millions of years forming a great valley with a river in the middle.

Waterfalls are formed when the softer rock that is under the hard rock is eroded forming a space under the hard rock that is called a plunge pool. When this happens, the water falls in a steep way.

Gorges can be formed in two different ways by waterfall retraction that is when the soft rock is eroded and the and the hard one falls and after many times that it happens there will be two rock walls after a waterfall. Another way is when a tectonic plate goes up and the other goes down. Then there extreme erosion happens and the plate that went up is now divided by the river.

In the Amazon the upper course is in the Andes mountains. The river goes through many gorges and waterfalls. The river systems and floodplains in Brazil, Peru, Colombia, Ecuador and Venezuela are called the upper Amazon.

Middle Course:

Meanders are formed when the outer side of a curve in the river has erosion and the inner part has deposition. Then a big curve will form.

Oxbow lakes are formed when a meander has deposition on the start of it and the river tries to find a new way past it so it erodes a straight line and a lake stays beside the river in the form of a bow.

In the middle course of the Amazon the water flows at a speed of two kilometers per hour.

In the basin flooding occurs between June and October.

Lower Course:

Flood plains are formed when there is a large river and a lot of deposition takes place so there is only a small stream but when there is too much water all the area that was once the river floods.

Deltas are formed very close to the mouth of the river. Deltas are formed when the water needs more space to flow into the ocean so it erodes many little streams that flow to the mouth. Here deposition also takes place, between the streams sediments are deposited in islands

The floodplains in the Amazon are made of many features such as shallow lakes, swamps and mangrove forests. The river mouth extends for 320 kilometers and it pours out 214 million liters of water per second in the Atlantic Ocean. The river Amazon does not have a delta because of its bore.

The coastline by the mouth is being eroded and muddy sediments are deposited.

Sources:

World Atlas. 8th ed. DK. Print.

"Sua Pesquisa - Portal De Pesquisas Temáticas." Bacia Amazônica. Web. 14 Sept. 2015. 

"Amazon River | Facts, History, Animals, & Map." Encyclopedia Britannica Online. Encyclopedia Britannica. Web. 14 Sept. 2015

"Amazon River." - New World Encyclopedia. Web. 15 Sept. 2015.

"Amazon Basin Facts." - National Zoo| FONZ. Web. 15 Sept. 2015.


My group also did a 3D model of a drainage basin