Aspectos naturais e antropogênicos associados ao rebaixamento do aquífero cárstico do platô de Irecê, Bahia.

Abstract

The Hydrogeological Basin of the Verde and Jacaré Rivers, located in the north-central portion of the State of Bahia, is almost entirely overlain by an area of carbonate sedimentary rocks, which constitutes an important karst aquifer in the semi-arid region of Bahia. The clayey soil, with its reddish-yellow hue and high fertility, along with the relatively flat topography, favors agriculture, which is one of the main economic activities practiced in the region. However, given the intrinsic characteristics of a karst environment in a semi-arid climate, the lack of surface water, caused by the existence of rapid percolation zones and sinkholes that absorb rainfall and quickly incorporate it into underground drainage, as well as high evapotranspiration necessitates the search for groundwater as a means of irrigation for cultivated areas. Nevertheless, in recent decades, human occupation in the region has intensified and with the increase in cultivation, there has been a rise in drilling of tubular wells, requiring a disorderly extraction of groundwater, lowering the aquifer and jeopardizing the water potential of that reservoir. Similarly, deforestation for agricultural occupation has led to the extinction of springs responsible for feeding the rivers of this basin, transforming intermittent rivers into ephemeral ones. Likewise, the uncontrolled use of nutrients and pesticides in agriculture has contaminated the aquifer and rendered its waters unsuitable for human consumption. On the other hand, the lack of control over human occupation without adequate infrastructure for solid waste disposal and without appropriate sewage systems has contributed to this contamination due to the great fragility of the karst environment. Thus, this work aims to show that there is an association between anthropogenic and natural factors that are leading to the degradation of the Irecê karst aquifer. This objective was achieved by cross-referencing the karst characteristics of the aquifer, hydrogeological data from tubular wells, land use and occupation data obtained from satellite images and historical rainfall data in the region. It was then possible to conclude that the entire Irecê karst aquifer is subjected to anthropogenic pressure which together with the natural conditions imposed by a semi-arid climate and low rainfall could lead to stagnation of this aquifer. Similarly, this study determined that the central area of the Irecê Karst Aquifer is experiencing the greatest anthropogenic pressure, compromising both the quality and quantity of its groundwater and requiring greater attention from the management bodies in this region. As a result, suggestions were made for implementing actions that, if conducted correctly could assist in the management of the entire Irecê Karst Aquifer, with greater emphasis on the central area, thus helping to control the degradation of this important aquifer in Bahia.