Lake Chapala’s Pollution – 2019

Lake Chapala Pollution

I have received a number of questions about the nature and degree of the pollution in Lake Chapala, originating from the recent series of articles I authored on this subject. I am a journalist, not a scientist. However, I am trained to sift through mountains of information to identify themes, strengths and weakness – as well as the essence of what the data indicates.

It must be noted that the environmental and public health hazards resident in the Lake Chapala basin are well researched and  well documented by scientific research from a number of disciplines. Most of this is available via internet search engines. Some is not. I acquired and reviewed both. I also interviewed public health, environmental, and other professionals directly involved in the endeavors of investigating the environmental and public health hazards that inhabit the Lake Chapala basin.

I posted an article about the transcript of the Latin American Water Council proceedings held in Guadalajara, Mexico. The genesis for much of the testimony that was provided during this court hearing came from this study: Institute of Technology and Higher Studies of the West (ITESO). In my opinion, this is one of the best studies because of the data set was longitudinal (2012-2018) and conducted by a team of very well regarded researchers. I discuss this particular study BELOW:


2018-08:  Quality Data Analysis Report: Department of Mathematics and Physics. The title of the research endeavor is: Report of Water Quality Data Analysis of Lake Chapala. Tlaquepaque, Jalisco: ITESO. It was published December 2018. The authors of this study are: Sánchez-Torres, Juan D .; Nuño-Sánchez, Saúl A .; Martinez-Alvarado, Juan C .; Ruiz-Cruz, Riemann Sánchez-Torres, J.D .; Nuño-Sánchez, S.A .; Martínez-Alvarado, J.C. and Ruiz-Cruz.

A team composed by Dr. Carlos Peralta, Lic., Loreto Irene Soto Rivas and Ing, Ana Sofia Macías Ascanio, Department of Sociopolitical and Legal Studies (DSOJ) of ITESO,) made a public records request to the Mexican Federal government. The information obtained by this team was via a request for transparency  on March 2, 2018 to the National Water Commission with the via folio number 1610100154118. This petition requested all the information that they (The National Water Commission) possessed related to the water quality of Lake Chapala. This team also prepared the formal complaint that was presented to the Latin American Water Tribunal at ITESO (Jesuit University of Guadalajara) October 22-26 2018. You can read the formal complaint and the outcome of these proceedings HERE.

The National Water Commission in Mexico is known as CONAGUA. (Comisión Nacional del Agua). It is an agency within the Mexican Federal government that acts as an administrative and technical advisory commission to Mexico’s Ministry of the Environment and Natural Resources (aka SEMARNAT). CONAGUA manages the nation’s waters, hydrological system, and engages in social development activities.

A database was created by the ITESO team of researchers and CONAGUA based upon the information they received from CONAGUA. This database contains information generated by CONAGUA about the presence of various elements detected in lake water samples obtained in some 34 monitoring stations located at different geographical locations around Lake Chapala. The chronology of this data was from November 21, 2012 to February 8, 2018.

The research team from ITESO selected only certain, specific elements contained in the database, which include: “Arsenic, Fecal Coliforms, Chromium, Biochemical Oxygen Demand (BOD), Chemical Demand of Oxygen (COD), Escherichia Coli, Mercury, Ammoniacal Nitrogen, Nitrates, Nitrites, Nitrogen Organic, Total Nitrogen, Orthophosphate, Phosphorus, Lead, pH, Total Dissolved Solids (TDS) and Solids Total Suspended (SST).”

Here are excerpts BELOW (quotes – translated to English) from the ITESO report (emphasis is mine):


Lake Chapala


The results of the present analysis showed that the monitoring stations, in general, have obtained higher than average concentrations are located throughout all the periphery of the Lake. It also realizes that all parameters, except Lead they have been detected in all the monitoring stations.

Arsenic: The samplings show that in Lake of Chapala, Arsenic has been detected.

Fecal Coliforms: It is necessary to indicate that Fecal Coliforms are from sewage discharges, as the name implies, come from the feces Fecal. In this regard, the NOM-127-SSA1-1996 and the WHO, specify that for water to be good quality there should not be a presence of these microorganisms. However, it is clear that there is presence of these in the Lake of Chapala, indicating that the water of Lake Chapala, in itself, is not drinkable. 

Untreated Wastewater: It is evident that untreated wastewater discharges are being made to Lake Chapala, and that in addition, in relation to this priority parameter, life is not being protected. 

Fecal Coliforms: All the stations have maintained, on average, a concentration that exceeds-by far-what is established according to NOM-001-SEMARNAT-1994. In that meaning it can be interpreted that:

 Lake Chapala does not meet any of the standards that protect the health of both people and ecosystems, in relation to the parameter priority of Fecal Coliforms (COLI_FEC). 

Aquatic Life: It is known that all stations maintain concentrations above the reference of Standard 001 that protects aquatic life.

 Polluted: The overall average of all measurements is 46.92 mg / L, which indicates the Lake is “Polluted”(Concentrations of Chemical Oxygen Demand obtained during the measurement period). “COD” measures organic matter caused by industrial residual water discharges. In that sense, this parameter officially relates water quality to industrial water discharges, and serves to indicate how affected the water of the lake is – by the aqueous waste of the industries with which it has some connection.

The stations located within Lake Chapala show high concentrations. 

Phosphorous: It is important to mention that the presence of Phosphorus in the water propitiates eutrophication phenomenon, which is considered as a problem of pollution by the alterations to the balance and to the dynamics of flora and fauna that have Lake Chapala as an ecosystem.

E Coli: The Fecal Coliform (COLLI_FEC) and Escherichia Coli (E_COLI) parameters are very much above the maximum allowed value, that is to say they violate by far the NOM-127-SSA1-1994 and in that meaning it can be said: 

the water of Lake Chapala has contained Fecal Coliforms, and in special E-Coli in concentrations that may pose a health risk and that should to be served with water treatment processes prior to distribution in the supply network.

These averages show that Lake Chapala has Fecal Coliforms in very high concentrations superior to all reference standards.

E Coli: According national and international references, for water to be potable it must not have presence of Escherichia Coli, in addition, wastewater discharges must have a concentration of 1000 NMP / 100mL to protect aquatic life, according to Standard 001. In this sense, with the global average has the approximation that the water of Chapala Lake per se is not potable, and it needs a purifying process to eliminate these bacteria, because they are pathogenic. It is known that all stations maintain concentrations above the reference of Standard 001 that protects aquatic life.



The above does not address the bodies of research on the contamination of aquatic species, avian species, ecosystem degradation, and the research documenting Chronic Kidney Disease among primarily indigenous populations that reside around the lake.

I hope this article helps those who have sent inquiries to me. I cannot reveal the source that provided with me with this research paper, prior to its public release. The graphic images contained in this article are also copyrighted (C) 2019 by Bill Dahl. ALL RIGHTS RESERVED.


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