Le «Pantanal da Nhecolândia» Mato Grosso: cadre physique et dynamique hydrologique

The “Pantanal da Nhecolandia” Mato Grosso: physiografic frame and hydrologic dynamics

Abstract

The immense plain of Pantanal of Mato Grosso (140,000 km2), situated in the central part of the South America (16°-22° S, 55°-58° W), corresponds to a still active continental base level. This plain is covered by Quaternary sediments, above all alluvial products of the effluents of Paraguay River, and is subjected to seasonal floods, due to hydrologic regime of the main river. The interpretation of Landsat-TM images has permitted to identify five parts, on the basis of «water landscape», vegetation, hydrologic dynamics and river network. The Nhecolandia region is directly influenced by the presence of the Taquari River to the west and of Negro River to the south. It presents a complex system of corixos and vazantes. The «Vazante de Corixao» region is covered by the savannah plants as well as the Taquari region. The former has few lagoons and is affected by the rising of the water level of the corixos and of the groundwater. Eastern Nhecolandia is characterized by the presence of an anasthomized system of corixos and vazantes and by the absence of cordilheiras and lagoas. In Central Nhecolandia the system baia-vazante-cordilheira-lagoa is developed. The floods are related to groundwater elevation and, in a minor part, to the corixos and vazantes that present a not well developed anasthomized character. A sub-region in the northern part shows a more narrow system of cordilheiras-lagoas, crossed by a wider corixos and vazantes system.