Aspectos físicos e qualidade da água da bacia hidrográfica do Ribeirão das Abóboras, no município de Rio Verde, Sudoeste de Goiás

Abstract

Ribeirão das Abóboras (Abóboras Creek) is the main water body which supplies the population of Rio Verde (GO) and it’s one of the main affluent of São Tomás River; the last being the main source of water supply of the city of Santa Helena de Goiás (GO). These municipalities are located in the microregion of Southeast of Goiás, with an economy based on agribusiness, whereas the municipality of Rio Verde is the main economy of this microregion. The physical characteristics evaluated, with the use of technologies, were the morphometry, the land use and vegetation coverage from 1985 to 2015 and the environmental fragility. The quality of water variables were temperature (T), hydrogen potential (pH), dissolved oxygen (DO), electric conductivity (EC), total dissolved solids (TDS), suspended solids concentration (SSC), apparent color (AC), true color (TC), turbidity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrate and total phosphorus (TP), since the averages compared with the limits for class 2 fresh water established by CONAMA Resolution 357/05. It was accomplished a study of the trophic state with the application of the Trophic State Index (TSI). It was possible to verify, through this study, that: this basin’s area is characterized as of a longer shape, in other words, it presents a lower propensity to great floods, if compared to a circular basin; the Creek presents water course characteristics with predominance of soft wavy relief, making it easy for agricultural practices; the basin is characterized as of average drainage density, inferring that the geological substrate and the pedological material are moderately poriferous; the land use and vegetation coverage, diversified from 2005 and in a deranged way, without respecting the limits imposed by the present environmental legislations, have caused important environmental damages, among them, water pollution, such as BOD and TP variables in disagreement with CONAMA Resolution 357/05 and high trophic state indexes, which vary from mesotrophic to hypereutropic. Such impact can cause damages to a proper water supply for multiple uses. Therefore, it’s necessary a land use and vegetation coverage planning, reconciling the economical interests with the environmental preservation and mainly the improvement of the quality of life of the population of Rio Verde and Santa Helena de Goiás.