Evidencias hidrogeoguímicas de mezcla de flujos regionales en el acuífero de La Muralla, Guanajuato

One of the sources that supplies water to the city of León, Guanajuato, Mexico, is La Muralla well field. Hydrochemical analyses, including major ions and lithium, of well and spring water samples suggest a sequential mixing process of three different end members, The first one, Comanjilla (C), is characterized by thermal influence and a deep vertical flow and has the highest chloride and lithium concentrations; its recharge occurs in the Sierra de Guanajuato, located to the NE of La Muralla. The second one, Tultitlán (T), has high chloride and low lithium concentrations and comes from the recharge area in the Sierra de Pénjamo. The third one, Muralla (M) has low chloride and lithium contents and is related to meteoric and local recharge. A bivariate scatter diagram of lithium vs. chloride shows that the mixing process may not be produced simultaneously between the three types of waters. Mixing is first accomplished between the end members C + T = CT and later, in the second mixture, a dilution process occurs with shallaw flows CT + M = CTM. The final mixture, CTM, represents the water extracted from the La Muralla well field.