USO E OCUPAÇÃO DO SOLO NO ENTORNO DOS LAGOS CAJARI E FORMOSO, PENALVA-MA, APA BAIXADA MARANHENSE, E SUA INFLUÊNCIA NAS VARIÁVEIS LIMNOLÓGICAS

Abstract

This work was carried out with the objective of verifying whether the soil use and occupation near the Lakes Cajari and Formoso, Penalva MA, in the Environmental Protection Area of Baixada Maranhense, exert influence on these lakes limnological variables. The study of the soil use and occupation was made by means of the analysis and interpretation of satellite Landsat 5-TM images from the two lakes studied, with 30 meter spatial resolution at the image bands 3, 4 and 5 regarding to the years 1990 and 2004. For the analysis of some limnological variables, two samplings were made in the dry period and one in the rainy period. The results for Cajari Lake indicated that the area occupied by the lake teorically remained the same, even after the construction of a dam near the town; the urban area has become tripled at that time interval; the capoeira vegetation left by the agricultural use were invaded by the babaçu vegetation; the extensive cattle creation is a human activity which is contributing for water chemical change and despite of all tensions which the lake is tolerating, such as urban occupation and deforestation at its margins, it maintain satisfactory their sanitary conditions. For Formoso Lake, the results showed it is well preserved in relation to Cajari Lake whereas it presented very discrete modifications, though their margins suffer constant collisions with the floating islands; it was not possible to evidence by means of satellite images the urban occupation near the lake because of the rustic model of residences, which is an important factor for its preservation. Comparing the lakes shape, Formoso Lake is stretched while Cajari Lake trends to a dendritic form. This fact explains the compartiment structure of the limnological characteristics verified at the last one. In conformation with the resolution N. 357/2005 of the National Environmental Council (CONAMA), the studied lakes are classified as freshwater bodies, category 2.