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22 nd Salt Water Intrusion Meeting: Salt Water Intrusion in Aquifers: Challenges and PerspectivesEVALUATION OF SALINISATION PROCESSES THROUGH ISOTOPICANALYSIS AND HYDROCHEMISTRY OF THE AQUIFER KARST SALITRE, THESTATE OF BAHIA, BRAZILTereza Cristina Bittencourt Nossa 1 ; Luiz Rogério Bastos Leal 2 & Maria do Rosário Zucchi 3& Antônio Expedito Gomes de Azevedo 41Htereza.nossa@cprm.gov.brH - 1 Serviço Geológico do Brasil (CPRM);2,3,4 Universidade Federal da Bahia (UFBA) .1 Av. Ulysses Guimarães, 2862, CAB. CEP: 41.213-000. Salvador-BA. Brasil.Abstract - The study area is located in the microregion of Irecê, located in the north centralpart of Bahia state, including a pilot area of the karst aquifer Salitre, defined in themunicipalities of Irecê and Lapão, part of the hydrogeological basin of the Green river andAlligator river. It makes up a total area of approximately 250km², consisting ofNeoproterozoic carbonate rocks of the Salitre Formation. This geological unit is the karstaquifer Salitre, which is the main source of water for irrigation purposes. A risk assessmentof salinization and sodification was carried out by a study of groundwater quality used forirrigation, with analysis of 40 physical-chemical parameters and isotope characterizationthrough deuterium, excess of deuterium, oxygen-18 and dissolved inorganic carbon (D, d, 18 O, 13 C CID ) in water samples collected from wells in the Salitre aquifer. Samples collectedin the eastern sector of the area, upstream, have a lower isotopic enrichment than thoseobtained from wells located in the area north-northwest, downstream flow, which showedhigher isotopic oxygen-18 ( 18 O) and deuterium (D) values, demonstrating that more wateris evaporated and subjected to interactions with the limestone throughout time. Theincreasing values of dissolved inorganic carbon ( 13 C CID ) highlight the fact that the isotopicenrichment occurs preferentially in the E-W direction, consistent with preferential flowdirections obtained in the area. The analyses of the water used for irrigation purposesshowed that in both periods of 89% of water samples are brackish and 11% saline. Coupledwith this, 89% of the groundwater analyzed were classified as C 3 S 1 , can normally be used forirrigation and only 11% of the samples were classified as C 4 S 1 , which are water should not beused for irrigation according to the danger salinization of soils.Keywords: hydrochemistry, isotopic analysis, water quality for irrigation, karst aquifer.77