Inovação metodológica na avaliação da qualidade ambiental urbana aplicada na bacia hidrográfica do Arroio Preto, Santa Cruz do Sul, RS, Brasil.

Abstract

The urban environmental sustainability is one of the great challenges of the contemporaneous society, considering that the environment in the cities has been gradually degraded by soil occupation following a traditional historic patterns based on the substitution of natural resources for elements of human interest. In this context, this research aimed at evaluating the urban environmental quality in the Preto Stream Watershed, Santa Cruz do Sul, RS, during 2016, through the measurement of some physical (PC), biological (BC) and anthropic (AC) characteristics, in order to develop an Urban Environmental Quality Indicator (UEQI). Data collection was based on information available in local management systems, evaluations in situ, computational programs of free access and interviews. Data processing was made by applying objective and simplified mathematical equations. The UEQI result is a value between 0 and 1, composed by the combination of 12 indicators, separated in three groups according to the type of environment evaluated, PC, BC and AC. The Preto Basin showed an UEQI value equal to 0.70, that signalizes a suitable condition in the urban environmental quality of the study area, highlighting the biotic environment with a value of BC = 0.77, owing to the presence of green areas which showing an index of 23,4 m2 hab.-1, value 212,7% higher than the Health World Organization (HWO) recommendation, which established 11 m2 hab.-1 as suitable performance for getting life quality to population, condition that places the Preto basin in a notability platform, beyond the parks and the urban forest, with an average of 101,6 ± 40,2 trees/km by linear sidewalk covered (CV = 39,5%), value that positions the region in a select group of places with high quantitative performance. These conditions show the great relevance of the forest called “Green Belt” in maintaining urban quality in the watershed. The physical environment showed a value of PC = 0.53, a low score getting by the soil characteristics and the water courses alterations, and warning the necessity to preserve the water quality, particularly in the lower reaches of Preto Stream, where it was verified a Water Quality Index (WQI) of 41,4 ± 10,0 (CV = 25,5%), corresponding to a low quality water Class, due to organic contamination and eutrophication processes. This fact coincides with the lack of coverage of sewage networks, since from the result obtained for this indicator, Ies = Zero, it is possible to point out the issue of sanitary sewage as a priority to be addressed in environmental management actions in the basin. The results also indicate an organized public environmental management structure, as well as a system of water supply and solid waste collection capable of meeting the local demands, as shown by the anthropic indicator (MA = 0.82). We conclude that IQAU is an innovative methodological tool for environmental management in urban areas, which can determine priority actions among the three environments (physical, biotic and anthropic) aiming at preserving the urban environment, in such a way the society is effectively integrated with the ecosystem services provided by the nature, in a sustainable fashion.