Avaliação da degradação ambiental da bacia hidrográfica do rio Peixe-boi, nordeste do estado do Pará.

Abstract

The watershed of the Peixe-Boi river, located in northeastern of Pará, it is facing an intense process of human disturbance of ecosystems, mainly due to the uncontrolled growth of agricultural activities and livestock. This work aimed to evaluate environmental degradation levels in said basin, through the analysis of multiple natural criteria under human pressure, in a GIS environment. For this, the work was organized in three specific objectives: (1) perform the morphometric characterization of the watershed (2) map and identify conflicts of land use in the PPAs, relating to water quality, and (3) identify and evaluate the natural vulnerability to erosion through multicriteria analysis. The study area was characterized as large, with 1.034Km² area, however, showed low drainage density and high permeability of the soil, being unfavorable to flooding. Its channels are slightly sinuous, with low slope and small bifurcation index, characterized as 4th order. It was found that 46% of PPAs of the study area, are in conflict of use, occupied mainly by grazing class (84%), and to a lesser extent by soil exposed classes and urban areas. It was recorded that the worst levels of water quality were related to irregular areas of use and occupation within the areas of permanent protection, especially in areas of high human disturbance near urban centers, where they were observed oxygen critical values dissolved, reaching 2,14mg/L, well below the values established by Resolution 357/05 of CONAMA. The environmental fragility of the watershed of the Peixe-Boi river, it was observed that approximately 47% of its area consists of classified environments as medium vulnerability to erosion, with large areas of pasture and agriculture, which are relatively degrading the soil types. The areas most vulnerable were the largest slope, near the mouth of the river system, presenting typologies Fluvisol and Gleysol Haplic, and ground cover predominantly type natural fields with some urban tracks.