Geoprocessamento aplicado à determinação da fragilidade emergente em um manancial de abastecimento público: a microbacia do alto do rio Sarandi

Abstract

The objective of this study was to characterize and evaluate the environmental fragility of the upper sub-drainage basin of the Sarandi River, an important source of public water supply in the municipalities of Realeza and Santa Izabel do Oeste, in the southwestern region of Paraná. Environmental fragility was determined according to the methodology of Ross (1994), based on slope, soil and current land use data. The crossing of the declivity map with the soil map generated the map of potential fragility and the crossing of the map of potential fragility with the map of land use and occupation generated the map of emergent fragility. Behind the land use and occupation map, it was possible to evaluate the current condition of occupation of the riparian forest areas. I have noticed that there are areas that present conflicts of use and occupation in these areas of permanent preservation, and agriculture currently occupies 34.63% legal area destined to the ciliary forests. Considering the potential fragility, it can be observed that in the Sarandi river basin the fragility classes comprised between low and medium represent 66.92% and those classified as strong and very strong represent 33.08% of the total area of the sub-drainage basin, while 49.98% and 32.45% of the area presented medium and high emergence fragility, respectively. The natural stability present in 66.92% of the area, does not exempt the sub-drainage basin from problems related to erosion, as this makes the soil more susceptible to be transported during periods of intense precipitation. With the removal of the vegetal cover this stability is broken, raising the level of fragility of the area.