Análise da água e das condições ambientais da bacia hidrográfica do Ribeirão das Pedras, Quirinópolis/GO

Abstract

This research was based on the perspective to understand the influence of land use in the physical and chemical indicators of water quality of the watershed of Ribeirão das Pedras - Quirinópolis / GO, which is the main source of public water supply in this city. As this area is occupied by domesticated animals raised in an agricultural setting to produce commodities such as food, it´s present on the land a common framework of environmental degradation due to the raising of the livestock. The objective of this research was to evaluate how much the occupation of the land can affect the water quality indicators and parameters from the integrated use of geo-physical and chemical analysis of the water. The parameters evaluated in situ, using the equipment Oakton PCD650, were temperature (T), hydrogen potential (pH), Electrical Conductivity (EC), Electrical Resistivity (RE), Salinity (SAL) and Total Dissolved Solids (TDS), based on the methods described in APHA. In laboratory, some data were analyzed for the concentration of suspended sediments (CSS). At fourteen sampling points, some samples were collected from October 2009 to September 2010. By using topographical maps, satellite images Landsat-5 TM and GPS data, allowed the elaboration of thematic maps of land use, vegetation, geomorphology, geology, soils and steepness of the slope, was able to create a geographic database in the application SPRING. Outcome of these data, we identified areas occupied predominantly by grassland classes (59.89%), Forest / Cerrado (22.30%) and exposed soil (7.98%). There is also a small expressivity the class Culture in the area, where it is represented with only 2.47%. In relation to geomorphology, the area is part of the geomorphological unit called Planalto Setentrional da Bacia Sedimentar do Paraná, where the higher altitudes vary from 600 to 900 meters high. As for the slope, most land in the watershed (88%) is among the categories of up to 12%, the ones that represent fragility vary from very weak to weak. As for the limnological characteristics, the temperature showed a medium of 24 ° C, and maximum 34.9 ° C, recorded at P7, in November 2009, and the minimum was 16.2 C, recorded at P1, in August 2010, thereby demonstrating the relationship with air temperature in the period, the pH values were close to neutrality in almost all points analyzed, only at P1 were more acidic, a fact explained by the presence of basaltic outcrop area of intense human influence; the P1 also showed higher values of electrical resistivity, 895.00 M.cm, which is explained by the lower presence of dissolved solids. The most significant differences of EC, TDS and salinity occurred at P2 in the rainy season; and the CSS analysis showed the highest values at Points 5, 8 and 1, respectively, these facts are explained by the practices developed near the collection points. With all the analyses in hand, we found out that the forms of occupation and land use are factors which are affecting the limnology of the area we have studied. Although the water in the watershed does not present inadequate conditions for use, according to the data evaluated in relation to CONAMA Resolution 357/2005, it should be preserved as it is through conservation practices to become a secure place of water supply for the future population.