Lerma River - Pollution

Pollution

The Lerma River has had chronic problems with pollution. Most of the problems are due to untreated and under-treated wastewater being discharged into the river. Reservoirs constructed to control the highly varied flow of the river are often choked with water hyacinths due to eutrophication caused by the untreated effluents. The most important industries in the Lerma River area are those that produce meat, dairy, produce, beverages, pulp and paper, leather goods, petrochemical and chemical products. Little or no emphasis on wastewater treatment and recycling has been imposed upon these economic activities.

The situation became extremely bad in the last 1980s because of erratic water policies that did little or nothing to regulate water use among competing interests and failed to consider the effects of upstream activities to those living downstream. Government plans were drawn up due to intense public pressure leading to improvement of the water quality in the 1990s. By 1997, 45 plants with a treatment capacity of 5.72 cubic metres per second (202 cu ft/s) were operating on a regular basis with an average running efficiency of about 70 per cent. Six further treatment facilities were under construction to raise the regional capacity to 9.56 cubic metres per second (338 cu ft/s). In Lake Chapala, into which the Lerma River flows, water quality improved from 90% of the lake having poor water quality in 1989 to 85% of the lake having good quality in 1997. However, the worst water quality was still closest where the Lerma River discharged into the lake.

However, in the decade beginning in 2000, contamination levels of the river system have again become alarming, with studies in Michoacán and Guanajuato documenting an increase in cancer and neurocysticercosis in populations that live near the river. The Lerma River portion of the Lerma–Chapala basin is considered to be the most polluted, especially in stretches closest to its source near Almoloya del Río. Since 2005, industrial contaminants have become a serious concern as well as the continuing loss of plant life in and around the river itself. In 2005, thousands of fish suddenly died in the river in the municipality of Pénjamo in Guanajuato state when effluent flow depleted the oxygen in that part of the river. The lower parts of the river, closer to Lake Chapala are in better shape because there is less urbanization there.