Condições sócio-ambientais da bacia hidrográfica do rio Caeté (Pará, Brasil)

Abstract

The absence of watershed management in Amazon inhabited areas has affected its natural resources over the past years. For this reason, this study focuses on the social and environmental aspects of 18 rural communities and the effects of wastewater discharge originating from Bragança’s city on the water quality of the nearby Caeté Estuary and its tributary, the Cereja River, located in the Caeté River basin. The adopted methodology to characterize the socioeconomic profile and the living and dwelling conditions was based on structured and semi-structured questionnaires applied to the local population. The domestic trash production was quantified and a determination was made of the composition of the trash, in some communities, from samples of around 20% of the residences. Water quality analyses of the main wells that supply the studied communities were carried out based on the determination of physical and chemical variables (turbidity, real color, apparent color, pH, temperature, dissolved iron and dissolved nutrients) and bacteriological studies (termotolerant and total coliforms). Field measurements (hydrological, hydrodynamic and-or microbiological variables) were taken in the most urbanized zone from Caeté estuary and Cereja river to characterise the water quality of those environments. The main environmental impacts were identified, georreferenced, photographed, and mapped. Guidelines were proposed for the effective management of the natural resources of the Caeté Basin by the pertinent local authorities. The obtained results showed that the Caeté River basin has approximately 2,207 rural families (9,573 inhabitants) and the majority of the population has low income, low education and low living and dwelling conditions. The services and infrastructure are inadequate and there is a lack of potable water, basic sanitation, trash collection, school, medical assistance, etc. On the other hand, Bragança´s city has more than 72,621 inhabitants living on an area of approximately 16 km², is one of the oldest colonial settlements of the Amazon region. Both studied rivers receive large amounts of wastewater disposed by private households, hospitals, workshops and fish processing companies and they have showed microbial contamination. The lack of effective public policy has accentuated both environmental and socio-economic problems. The authors suggest several measures to improve the current situation, including: (i) the regulation of land use to reduce the environmental impact of the economic sector; (ii) implementation of management programs for the sustainable exploitation of natural resources (fish, crabs, clay, lumber); (iii) installation of public services, in particular piped water and sanitation; (iv) better monitoring and penalization of the illegal exploitation of natural resources.