Estudo morfológico e hidroquímico de pequenas depressões na Nhecolândia, Pantanal, MS / Morphological and hydrochemical study of small depressions in Nhecolândia, Pantanal, MS

AUTOR(ES)

Tatiana Mascari Parizotto

FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

28/09/2012

RESUMO

The southern part of the Taquari alluvial fan, called Nhecolândia, is a sub-region of the Pantanal of Mato-Grosso exhibiting a complex of round shape lakes, draining fields, forested sandy areas, small watercourses and small depressions. Former studies have shown that the sub-superficial water fluxes depend on the intensity of the flood and on the presence and shape of a sandy clay loam greenish horizon, locally cemented, which acts as an impervious layer and drives lateral fluxes. Although its presence has always been associated to the alkaline-saline parts of this singular landscape, it also occurs below small freshwater depressions. The objective of this study is to understand the hydrological functioning of these small depressions in relation to the soil cover layout. Electromagnetic induction methods were used to draw apparent electrical conductivity (CEa) maps, crossed with direct auger holes and pits observations, and laboratory analysis (grain size distribution and mineralogy). Physico-chemical analysis of the ground water in the depressions and a monitoring of the groundwater fluctuation along one year were also performed. The greenish horizon, more or less cemented, occurred at the base of the soil system in all the studied depressions. It was overlaid by more sandy horizons. The main pedological differentiation was organic matter and iron redistribution along the soil sequences, in relation with the hydrological regime. During the dry season, the watertable goes down and the greenish horizon acts as a threshold, disconnecting various watertables in the different parts of the landscape. Along the year, the closed depressions accumulate the water only temporarily and fleetingly. Most of the time, they work as areas of water redistribution towards the surrounding landscape units, and therefore have a essential function in the Nhecolândia.

ASSUNTO(S)

apparent electrical conductivity condutividade elétrica aparente funcionamento hídrico hydrological functioning iron redistribution lençol freático morfologia dos solos pantanal pantanal wetland pequenas depressões redistribuição do ferro small depressions soil morphology watertable

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