The San Cristóbal volcano is the highest and one of the most active volcanoes in Nicaragua. It is located in the Volcanic Complex that bears its name and includes five volcanic structures: San Cristóbal, Casitas, Chonco, oyotepe and La Pelona. San Cristóbal is the most active of the group. It emits gases continuously and from time to time there is seismic activity around it. In the present study, a sample of waters around the volcanic building that had some hydrothermal alterations (temperatures above room temperature) was carried out, after the analysis of the samples it was observed that the water samples had a pH of 6.5 slightly acidic and Temperatures on average of 50 ° C in two of the three studied sites, on the other hand, were characterized the waters studied as of meteoric origin shallow convectively heated by a source of magmatic origin this due to their high concentrations of bicarbonates which Oscillate between 140 and 350 mg / kg evidenced in the ternary and Pipper diagrams.