Behaviour of the groundwater system in the Santa Catarina area, Mexico City

In the southeast area of Mexico City a line of 14 wells exist and are used as a potable water supply for surrounding towns. The average distance between each well is approximately 400 m. Each well was drilled to an approximate depth of 400 m. The results of vertical electrical soundings, performed as part of another study, indicated the presence of mineralized water down to a depth of approximately 200 m with potable water beneath. The granular aquifer is bounded by basaltic flows related to the Sierras de Santa Catarina in the north and the Chichinautzin in the south. To aid in the determination of the age and origin of the different groundwaters indicated by the geophysics, a geochemical and isotopic monitoring program was completed. Geochemical analysis was limited to the major ions. Isotopic analysis included 18O, 2H, 3H, 34S and 14C. Geochemical and isotopic data was significantly varied within the well field. The geochemical, isotopic and geophysical data was combined to produce a hydrogeological and hydrogeochemical qualitative model for the aquifer that exists around the Santa Catarina well field. (author). 11 refs, 3 figs, 7 tabs