Caracterização hidrodinâmica e hidroquímica do aquífero Boa Vista na bacia do Rio Cauamé-RR

Abstract

The choice of the Cauamé basin for this study is due to the need to implement water resources management policies in Roraima, in which the Professional Master's Degree Program Profágua plays an important role as it instrumentalizes professionals and master's students build the deepening of the knowledge of water resources. This region has the highest concentration of enterprises and also the highest population density in the state. The scarcity of information on hydrogeological knowledge leads to ignorance about important elements in the control of groundwater flow, especially in the processes of recharge and discharge, as well as the natural conditions of storage waters, leading to implications in processes of management, regulation and granting of the use of water resource. The scope of this work is to characterize hydrogeologically the Boa Vista Aquifer System (SABV) in Cauamé river basin, which is located in the central-northeast sector of Roraima State. For this purpose, the CPRM (SIAGAS) database was used to register wells. Besides the historical data, water sampling and drilling campaigns were carried out in which, at the time of collection, physical-chemical measurements were made, as well as pumping tests, in order to obtain a current characterization of the research area, from which the hydrodynamic parameters were verified. The results suggest that Boa Vista Aquifer is an underground reservoir, formed mainly by sands predominantly medium to coarse granulometry in the edges of the basin and fine to medium in the central regions, occupying the area of 1. 803.00 km2, which is equivalent to 57% of the total extension of Cauamé Basin, whose measured hydraulic conductivity varies from 1.2 x10^-2 cm/s to 3.2x10^0 cm/s, and these values suggest a vertical heterogeneity along the stratigraphic stacking, with predominant direction of the underground flow from northwest (NW) to southeast (SE) with discharge in the Rio Branco trough. The hydrochemical characteristics reflect the mineralogical composition of the rocks that contain and there is a correlation between the chemical composition of the underground waters, the circulation conditions and the lithology, the underground waters have been separated into two distinct groups: chlorosulphated and sulphated. The study also concluded that the levels of nitrite and nitrate found suggest that reservoir is free of domestic pollution in the regions studied and the ammonia values in Monte Cristo region may be associated with the use of fertilizers.