Vulnerability to salinization due to marine intrusion in a coastal aquifer in the State of Ceará

Abstract

Coastal aquifers are an important source of water supply for the State of Ceará, especially during the dry season, when surface reservoirs are not at their full volumes. In this way, these aquifers are often affected by the problem of marine intrusion induced by inadequate exploitation. The present study was developed with the objective of identifying the degree of vulnerability to salinization by marine intrusion for the Dunas/Barreiras coastal aquifer system in the Municipality of Icapuí, Ceará, as well as evaluating the quality of groundwater based on parameters associated with salinization, in view of its importance for the region, as it constitutes the main source of water supply. For this purpose, the GALDIT methodology was applied, which uses mappable indicators, represented by the type of aquifer, hydraulic conductivity, potentiometric surface height, distance of the wells from the coast, rCl^-/rHCO₃^- ratio and saturated thickness, to quantify and classify the vulnerability from coastal aquifers to seawater intrusion. The results indicated areas with medium and high vulnerability to salinization in the aquifer system, defined mainly by the distance of the wells in relation to the coast, the height of the potentiometric surface and the rCl^-/rHCO₃^- ratio. In relation to the concentration of salts, the quality of the groundwater is compromised in more than 60% of the analyzed samples; however, this salinization is probably more related to marine aerosols and/or the infiltration of brackish waters from coastal lagoons than the mixing of marine and continental groundwater promoted by saline intrusion. On the other hand, the vulnerability of the Dunas/Barreiras aquifer system in the area requires greater attention in relation to the management of water resources, since changes in current demand, with a consequent increase in exploitation, may lead to the advance of the saline wedge towards the continent.