Análise morfométrica de lagos nas áreas aplainadas do Nordeste de Roraima - Brasil

Abstract

In the northeast portion of the State of Roraima, in Pediplano Rio Branco - Rio Negro, more precisely in the ‘Formação Boa Vista’ we find an extensive flat area, covered by ‘savannas’, where several lakes are placed presenting very variable forms, depths and extensions. The morfometric measures of those bodies of water were acquired through the application Arc View 3.2, Software of Esri, on the image of satellite of Landsat 5, obtained on April 2, 2006, in the point 232/58 and of field works. Thus, the present research has for objective to accomplish the analysis of the space and morfometric distribution of those lakes through the hidrology, stocked water and fisiografy in the flat areas of the described area. The lakes present circular, subcirculares and subretangulares forms. The lakes of the area are perennial, they lose part of their volume of water stocked in the dry period, but they don't dry. In the area B, the lakes are strongly influenced by the ‘sazonalidade’. When evaluating the intermittent character in 19% of the lakes analyzed in satellite image, the remaining - 81% - presents a reduction almost that total of the mirror of water. Those lakes are linked to one or two drainage channels, they present a great density of aquatic ‘macrófitas’, that are distributed along the depressions and they are fisiografically harnessed to soils areno - loamy that happen in soft-wavy reliefs the wavy ones, also happening the ‘lateritas’ presence in the area A. The direction of this area is probably conditioned to the flaws related to the neotectonic. In the area A prevails the direction NE SW and, in the area B, the direction prevails L to W. Those lakes increase their volume of water substantially stocked in the rainy period. The lacustrine density in the area A is of 1% in the dry period, arising for 2% in the rainy period; in the area B it is of 0,6% in the dry period, arising for 2% in the rainy period. Thus like in the area A as in the area B the lakes represent very little of the selected total area.