Análise dos impactos do uso e ocupação do solo na qualidade da água da sub-bacia do São Gonçalo, Cuiabá, MT

Abstract

Unplanned occupation has resulted in the degradation of the environmental quality of urban spaces, with strong impacts on water resources as a reflection of this disordered occupation process. This work aimed to evaluate the anthropogenic influence on water quality and to provide subsidies to establish water quality targets to be defined in the regulation of the framework for the sub-basin of the São Gonçalo stream, a tributary of the Cuiabá river. The VERAH method was used to diagnose the situation of the components: vegetation, erosion, residues, water and housing in order to verify the interface of use and occupation with environmental variables. Water quality campaigns were carried out from December 2016 to November 2017 at three points in the sub-basin, in order to verify if there was a change in quality upstream and downstream and in periods of drought and rain, with the application statistics and box-plot graphs. The sub-basin presented 52% of all its area comprised of vegetation cover, 41.98% occupied with buildings, and 4% with exposed soil. Only two neighborhoods, Parque Cuiabá and Tijucal, that are located in the study area were contemplated with urban planning and infrastructure before occupation, the other neighborhoods were originated from irregular occupations in the areas adjacent to the urban nucleus of Cuiabá. Through the analysis of water quality data it was possible to observe if the framework established for the main channel of the basin was adequate to the characteristics and needs of the water body. The identification of the lack of water, sewage, drainage and waste infrastructure in the sub-basin made it possible to establish a cause and effect relationship in urban occupation and environmental degradation. The native vegetation was suppressed in large part to give space to buildings and public roads drawn irregularly. The present erosive processes have laminar origin, in soil sites exposed by deforestation processes. Several sites of inadequate disposal of domestic solid waste and civil construction are recurrent, spreading several pockets of waste along the sub-basin, affecting the quality of water that has proved to be poor or poor within the IQA. From the quality data analyzed it was possible to observe that from the source to the mouth, the stream is very degraded, with levels of pollutants that are outside the one that the environmental legislation recommends. The provisional framework also did not prove adequate for the bands and classes for which it was established, showing great permissiveness regarding pollution by the established resolution. In this sense, this research provides a framework proposal for the channel to reach class 2 for the quality of rivers over a 10-year horizon. In order to modify the current scenario, the prognosis establishes the adequacy of urban infrastructure and especially of sanitation, awareness campaigns and reallocation of the population that occupies the preservation areas.