The repeatability, reproducibility and accuracy of the direct measurement of δ(D) and δ(¹⁸O) isotopes in water samples were evaluated using Cavity Ring-Down Spectrometry, and values comparable with the Isotopic Ratio Mass Spectrometry were obtained. Memory effect correction was negligible after five successive injections, and the time for each sample analysis was approximately 70 minutes. Application of the method to Brazilian bottled mineral water has shown that it is possible to trace the origin of the water to at least the state level within Brazilian geographical regions. National and regional meteoric water lines were constructed with substantial differences between geographical regions, in particular for the central region of the country, with a slope coefficient of approximately seven and no deuterium excess.