Water Quality Assessment of the Santiago River and Attenuation Capacity of Pollutants Downstream Guadalajara City, Mexico

The Santiago River in Mexico has been seriously polluted because of rapid urbanization and industrialization activities, lacking of appropriate planning and contamination monitoring policies. This research characterized the river water quality and recognizes some overall pollution sources, using two different information references: a dataset of 5 years from the Jalisco State Water Commission and a 14-year dataset from the National Water Commission. Two zones have been identified as the main sources of pollution (hotspots), where the major events of urban and industrial wastewater discharges occur: (i) the urban fringe of Guadalajara city, with special emphasis in its southern area (nearby the so-called El Ahogado stream) and (ii) downstream of Guadalajara City. Nevertheless, we have recognized some areas along the Santiago River where significant reduction of pollutants concentration takes place, possibly due to dilution by the inflow of tributaries and to the rainfall increasing. In addition, it is likely that hydropower dams are positively influencing the retention of pollutants along the river. In the lower zone, the water concentrations of O are consistently above acceptable levels (up to 5 mg L), and the majority of the pollution indicators parameters are below the maximum permissible values, despite the high pollution in Guadalajara area. This paper attempts to offer a methodological approach for a more accurate assessment of the river water quality and may assist in interpreting the sampling results derived from the regular monitoring, conducted by the state water authorities, while emphasizing the natural attenuation capacity of the Santiago River. Copyright © 2015 John Wiley & Sons, Ltd.