Avaliação do aquífero cárstico Jandaíra na região de Baraúna, Rio Grande do Norte

Abstract

The study area is located in the region of Baraúna-RN city, extreme West of the State of Rio Grande do Norte. It covers an area of 675 square kilometers, including the Municipality of Baraúna, and part of the municipalities of Quixeré-CE and Mossoro-RN. The Jandaíra aquifer constitutes the hydrogeological unit and it is the object of this work. It is an aquifer of carbonate rocks used in the water supply of urban and rural population, mainly of the irrigated fruit-growing. The objective of this work is to evaluate the hydrogeological behavior of the Jandaíra karst aquifer, to verify its conditions of use, to evaluate the underground flow character, to propose the conceptual model, and to answer questions about the lowering of water levels. For this, was performed the survey of the existing data for the area, the elaboration of maps and interpretation of images, the elaboration of well profiles, the hydrodynamic parameters survey, the underground flow evaluation, the recharge evaluation and generation of the model conceptual schematic. Based on existing data, the area was subdivided into three zoning for karstfication and identified by geophysical methods and schematized in the conceptual model with the aid of structure maps, well profiles and identification of karst in the region. The area has strong exploitation of the water of the Jandaíra aquifer with use mainly in irrigated fruit-growing as shown by the study of water use in the region. Also were prepared the reserves estimates based on the water level variation in selected wells. The related studies to underground flow showed a natural flow tendency in the SW-NE direction, but the strong influence of the water exploitation caused a convergence for the central sector of the area. The construction of the conceptual schematic model aimed to identify the different structures presented by the aquifer in the region, showing the variation in karstic development. The recharge calculation showed the high potential of the Jandaíra aquifer, with an average yield of 45%, the analysis of rainfall records and static levels showed that the cause for groundwater retraction has two important factors: The strong exploitation of the waters combined with the prolonged droughts.