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"Dequada"

In the Swampland, it happens a natural water quality deterioration phenomenon, denominated "Dequada", related to the great organic decomposition mass, that it happens at the beginning of the flood process in the Swampland and depending on the magnitude can provoke a great kill of fish.

The intensity of the drought in previous year results in the amount of plants that will suffer decomposition with the subsequent flood, and promotes the water deterioration phenomenon.

In 1995, the phenomenon was very expressive, due to speed and to the great volume of the flood wave, presenting dissociated values of carbon gas of up to 79 mg / L
The full period of Paraguai River it reaches Corumbá in April - May - June.

The annual cycle of flood and drought is the more important ecological phenomenon of a river. The area of flood inclusion and the time of permanence of the waters in the fields dictate the readiness of habitats and feeding for the fish, crustaceans, birds, reptiles, many mammals, aquatic plants and semi-aquatic.

The waters cycle is, therefore one of the factors that rules the biodiversity of the Swampland, once which favors the vegetable and animal species, related to the drought phase, and it favors the related species of the flood phase. Vegetables that grow in the drought phase and die in the flood phase, will supply nutritious and salts the water, contributing to the development of other species.

That area periodically flooded form transition areas between the aquatic and the terrestrial enviroments. That is denominated of ecótonos and present high biodiversity.