El papel del sustrato geológico en el escurrimiento superficial y en los acuíferos del campo geotérmico Los Azufres

Abstract

The infiltration and storage potential of the catchment area in the geothermal field at Los Azufres, Michoacan, were analysed to determine the origin of its deep recharge. The study is based on measurements of the surface runoff systems at the end of the dry period. The role the lithological composition of the region is directly reflected by the water volume in the aquifers for each geological unit. This serves as a basis for the classification of the hydrological units: (1) the Andesite Basal Complex (main reservoir of the deposit) with a variable infiltration potential caused by the heterogeneity of fracturing and hydrothermal alteration; (2) the Agua Fría rhyolites with restricted infiltration from fault fractures; (3) the impermeable San Andrés and Mozo Domes with no infiltration potential; (4) the Yerbabuena rhyolites with the El Bosque and El Rosario Domes with a high capacity for deep infiltration through radial cooling structures; and (5) the El Guangoche Dome with low permeability characteristics. The volume of the surface runoff at the end of the dry season is just 6% of the total rainfall. This value represents the lower limit of the storage capacity of the perched aquifer system at the foothills of the Los Azufres mountains. Most rainfall is lost through evaporation, surface runoff during the rainy season and deep infiltration.