O ÍNDICE DE SUSTENTABILIDADE AMBIENTAL DO USO DA ÁGUA (ISA) COMO FERRAMENTA DE CONTRIBUIÇÃO ÀS POLITICAS PÚBLICAS DE DESENVOLVIMENTO E CONSERVAÇÃO NA BACIA DO RIO BACANGA, SÃO LUÍS/ MA.

Abstract

A hydrographic basin is a complex environmental system, resulting from the interrelations between the physical-natural and socioeconomic subsystems. It s identity as the unifying of environmental processes and human interference is leading to its adoption as a research unit. It allows from the analysis of the physical-chemical, biological and socioeconomic factors the evaluation of the quality and sustainability of the environment. This works aim is the composition of an Index of Sustainable Use of Water (ISW) which may subsidize the adoption of public policies towards sustainable use of water resources. For the construction of the ISW were analyzed two dimensions: the ecological one and socioeconomical one. Physico-chemical indicators (pH, dissolved oxygen, ammonia, nitrate and phosphate), biological indicators (phytoplankton) and the index of environmental preservation (EP) were used to analyze the Ecological Dimension (ED); to analyze the Socioeconomic Dimension (DS) were used as indicators income, education and sanitation. This way was generated an index for the five sub-basins of the Bacanga river basin and the basin as a whole. Past data published by Martins (2008) and Costa (2008) were used for the physico-chemical and biological indicators. The results of applying the ISW are lined not only on the proposal of a tool in assessing the sustainability of the Bacanga river basin, but also on the ability to identify the main responsible for the advances and setbacks in the quest for sustainability. The 5 ((Jambeiro) sub-basins studied had significant impairment of sustainability. The lowest index, 0.29 was found for the sub-basin 5, revealing a weak sustainability. The sub-basins 3 (Mamão) and 4 (Gapara) both had the value of 0.36, demonstrating a committed environmental quality of these environments. Only the subbasins 1 (Barragem) and 2 (Bicas) had a higher rate compared to the others with 0.43 and 0.42 respectively. These sub-basins despite having an older population growth and therefore a greater impacted area, has good services like water supply and provision of schools. The ISW for the Bacanga river basin was 0.37 indicating it as a polluted environment. Thus the assessment of environmental quality of the Bacanga river basin reveals the consequences of a mode of urbanization governed by private economic interests over the welfare of the community, a process that creates and reinforces social inequality and exclusion (which is reflected in sociospatial segregation and vulnerabilities differentiated to natural hazards) and degrades the physical nature. As complementary and opposite sides of this form of urbanization the basin shows on one side the saturation of the carrying capacity of the physical-natural subsystem in areas in which it promotes urban occupation, a situation caused mainly by high soil sealing and high population density, on the other hand, it appears that the areas of greatest natural vulnerability tend to be occupied by the socially excluded and most vulnerable to environmental risks, feeding a dynamic in which lower quality of life and low environmental quality are mutually reinforced. As mitigation measures to modify this reality one can measure the local economic development with its generating jobs and income, the digital divide with the deployment of telecentres , the articulation of social protection network (family register), the expansion and improvement in services water supply, garbage collection and sewage treatment as well as urban drainage, rehabilitation of the sewage plant (ETA) of Batatã, the recovery of the Bacanga dam to regulate the water flow, preventing flooding, the relocation of residents in the areas of risk, the respect to the limits of the Bacanga State Park and the adopting of solutions that contribute to the recovery and preservation of protected areas and environmental interest. ISW has proved to be an appropriate tool to support decision makers and policy makers in the process of building more sustainable ways to the society.