RESUMEN
The aim of this work was to evaluate the metals content in surface water of Arroyo San Ignacio (San Ignacio stream) and its main tributary, which are located in a priority ecological region of Mexico. For this study, these streams were divided in three sampling zones establishing thirty two sampling sites. Al, As, B, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Se, Si and Zn were measured. Some physicochemical parameters were also evaluated. Results indicated significant difference (P≤0.05) in pH, electrical conductivity, total solids, Ca, K, Na, and Mg levels for the three zones but no differences in heavy metals contents were found. Results were compared with Mexican and international standards and showed that seven metals (Al, Fe, Ni, Mn, Cr, Pb and Cd) exceeded drinking water standards. This pollution is mainly due to increased anthropogenic activities in the region and will likely worsen in the future due to unsustainable practice of discharging wastes into the streams.