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Water Cycle....

Weißwasser - Amazonas -  Nährstoffe

The most powerful river on earth, the Amazon, is the most famous example for a whitewater river. Since the river comes from young mountains, as the Andes are, it has an especially high concentration of organic nutrients


The dark color of the blackwater comes from dead plant remnants, from which humin acids come. Its pH is between 4 and 5. .

Rainy season temporary pond with blackwater.

Peru Rainforest Amazon Pachitea Llullapichis Panguana Species Diversity : Wasserkreislauf

Climate and water cycle. Several times a day one gets the impression that there is a train thundering its way past in the distance, and yet there are neither tracks nor streets here. It is the rainy season and the approaching cloudbursts can be heard from a long way off. Up to 3000 millimeter rain falls annually here per square meter (in Germany it is between 700 and 1000 millimeter). Huge amounts of water pour down on the forest. Otherwise harmless rivulets become torrents within minutes; rivers rip up trees, cause riverbanks to slide and take torn up huts and boots with them. A river often changes its course overnight or flows into another river exactly on the spot where a farmer had his hut the day before.

Rain forests develop in regions where there is constantly a lot of rain. Here the monthly precipitation is at least 100 millimeter per square meter. Depending on the geographical location periods of more rain and less rain may alternate.

A main characteristic of tropical regions is the constantly high temperature, with a monthly average in the coldest month of minimum 18 degrees Celsius. In many areas the drier periods are called summer and the rainier winter. If the air temperature is the deciding factor for seasons nighttime would have to be considered winter, since the temperature differences are greater over a day than over a year.

The forest waters itself.

The entire Amazon basin lies in the area under the influence of tropical air currents that circulate to the north and south of the equator. The location and character of the Amazon create an extreme uniformity in temperature, humidity and vegetation density.

The plant ceiling is especially important for precipitation. Trees, plants, earth that never dries even on the surface, leaves, streams, rivers and ponds together build a huge, wet sponge. Because of the intense rays of the sun moist air rises and collects into dangerous looking thunderstorm clouds, in which the humidity condenses into rain drips when it reaches the cooler air levels. These raindrops fall with a roar back onto the leafy ceiling, and thus the forest waters itself. This local "small water cycle" is one of the foundations of life in the tropical forests.

The circulation of air masses above the rain forest is not the only source for the high precipitation, however. The trade winds from the Atlantic play a large role, in that they deposit the warm, humid air masses as snow or rain on the Andes. Source streams flowing through mountain and mist forests provide the Amazon basin with a continuous and unimaginable amount of water.

Evergreen rain forests thrive everywhere in tropical countries where the annual rainfall is at least 2000 millimeter. This is in fact the case in most regions of the Amazon. There are gradual differences though; the areas of the Amazon with the most rainfall are the northwest and northern Amazon estuaries.

Wet season — dry season

Sunshine, and thus the amount of evaporation, is highest when the sun reaches its zenith. The zenith is reached twice a year between the tropic of cancer and the tropic of Capricorn, which means that the Amazon basin has two rainy seasons and two dry seasons. The rainy season in northern Amazon is from April to August, while it is from October to April in the south. This means that the Amazon has a fresh supply of water in alternating rhythmic periods. One might call it a permanent tide pulse. This is very clear when the rainy season starts in the southern areas. The largest tributaries of the Amazon are in the south, and their water levels can change the level of the river by up to 16 meters.

Text und Fotos © Andreas Schlüter 2003-2004