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Contribuicao de diversas tecnicas isotopicas no estudo do aquifero carstico da regiao central da bahia (irece-iraquara)

1980; Sociedade Brasileira de Geologia; Volume: 10; Issue: 2 Linguagem: Inglês

10.5327/rbg.v10i2.183

2317-4889

Antônio Plata Bedmar, Adelbani Braz da Silva, Fernando Gomes Jardim, Luiz Barreto de Oliveira,

Groundwater and Watershed Analysis

The karst of the central region of the state of Bahia (Brazil) has been studied by using different isotopic technics, which included: a)determination of the well profile with artificial radioisotopes for flow measurements; b)analyses of the environmental isotopes, deuterium, oxigen-18 and tritium. The isotopic profiles of the wells allowed determinations of the distribution of the fracturing and the karstic structure of the aquifer as well as the calculation of an approximate value for the effective porosity of the transmissivity. The transmissivity obtained by using these methods agree with those calculated using the pumping test. The stable water isotopes allowed the identification of four different aquifer zones being important to establish the general ground water flow. It was also verified that the water experiences evaporation before infiltration in two of these zones, characterizing them as recharging zones. An exponential model of water renewal was utilized to determine the aquifer recharge in different zones based on tritium determination. The water volume was also evaluated in the aquifer by using the porosity from the isotopic profiles. The following isotopic technics were used: 1)well profiles using artificial radiactive tracers; 2)measurements of the stable water isotop concentrations (deuterium and oxigen-18); 3)measurement of the thermonuclear tritium; 4)test with radioactive tracers to measure the effective porosity; 5)measurement of the source flow utilizing iodine-131 as a tracer. The present report describes the results of the first three items. Due to the reduced number of tests the results obtained are not statistically representative and measurements of the source flow were only completed to support the system hydrogeological interpretation.