How water reaches Guadalajara, how the Santiago River became polluted, and why in October 2026 hundreds of neighborhoods were put on rotating water cuts.
Information current to: Oct 21, 2026Reading time: 12 minMario Daniel Muñoz RíosVersión en español
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I
The journey of the water
Before talking about pollution, we need to know where the water travels. Guadalajara does not depend on a single source or a single pipe.
The main source2017–2022
A distant lake supplies the city
Lake Chapala, the largest lake in Mexico, lies about 45 km from Guadalajara. Between 2017 and 2022, of the 10.1 m³/s that SIAPA, the metropolitan water utility, distributed on average, 6.3 m³/s came from the lake: more than six of every ten liters.
The lake receives the Lerma River from the east and drains through the Santiago River at Ocotlán. Two routes run from the lake to the city, built 35 years apart.
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The flow distributed is not the same as the volume granted in concessions or the design capacity of the works. These are annual averages: they change with the lake level and with how the system is operated.
The first system to carry water from Chapala to the city began operating in 1956, with a permit for 4,000 liters per second. Today it is called the sistema antiguo, the old system.
At Ocotlán, lake water is pumped into the Santiago River. There the river also receives the Zula, which comes down from Los Altos carrying discharges from tequila, manufacturing, farming and livestock operations, so what is diverted downstream is not only lake water. The water flows along the riverbed to the Corona diversion dam, where part of it is sent into the Atequiza canal. It reaches the La Calera dam, where a pumping plant sends it along the Las Pintas canal to the dam of the same name, and from there to the Miravalle treatment plant (PP1).
Almost the entire route is open to the air: between fields, villages and, over time, neighborhoods and factories.
Why does the Atequiza canal matter?
It is a link in the old system: it receives the water diverted at the Corona dam and carries it to La Calera, before Las Pintas and Miravalle. That is why water quality has to be checked along every stretch, not only at the Las Pintas dam. It is not the Santiago riverbed at El Salto and Juanacatlán: the diversion is upstream.
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The Atequiza and Las Pintas canals are INEGI line work (1:50,000 topographic charts). The dotted stretches (La Calera → Las Pintas canal and Las Pintas dam → Miravalle) are schematic: they connect known points and do not follow surveyed pipes. The location of Miravalle is approximate. Names of the stretches vary: the state water commission (CEA) calls the whole open canal that crosses Ixtlahuacán and Tlajomulco toward Miravalle the Atequiza canal, while INEGI charts distinguish the Atequiza canal (up to La Calera) from the Las Pintas canal. It is one system.
In 1978 SIAPA was created to serve Guadalajara, Zapopan, Tlaquepaque and Tonalá. The city was growing fast: in 1979 it received 7.7 m³/s, 81 % of it from Chapala; by 1984 it was 9.65 m³/s.
Between 1984 and 1991 the Chapala–Guadalajara aqueduct was built: 42.6 km of pipe with a capacity of 7.5 m³/s. It takes water straight from the lake and does not pass through the river or the Corona dam. That is why it kept working when the open route was shut down in 2026.
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The violet line joins the unnamed aqueduct segments that INEGI maps between the lake's north shore and Miravalle. Identifying them as the Chapala–Guadalajara aqueduct is our inference, based on route and length: the measured path adds up to about 44 km versus the 42.6 km documented. The dotted gaps are stretches that do not appear on the chart. The intake is marked approximately.
The city also uses wells and springs, and the Calderón dam, which since 1991 has sent water through a 31 km aqueduct to the San Gaspar treatment plant (PP3) in Tonalá. In 2021, Calderón stopped supplying water from March to August because it ran dry.
6.3
2.8
1.1
old system: up to 2.5 m³/s
Chapala 6.3 · aqueduct and old system
Wells and springs 2.8
Calderón 1.1
m³/s, 2017–2022 average (McCulligh 2024). The old system's maximum is a Jalisco government figure (2026).
The El Zapotillo dam, on the Verde River, was completed in August 2024 and is part of the El Zapotillo–El Salto–La Red–Calderón system, which carries water to San Gaspar. In October 2026, the state government reported that this system was running at 45 %.
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The El Salto dam in this system is in Los Altos de Jalisco; it has nothing to do with the municipality of El Salto. The chart's figures do not include El Zapotillo. The sum (10.2) differs from the reported total (10.1) because of rounding. The green lines are unnamed aqueducts that INEGI maps in the Calderón–San Gaspar corridor.
Every route ends at a drinking-water treatment plant. There, water from the lake, dams or wells is cleaned and disinfected. Then it flows into tanks and into the pipe network that takes it to homes.
PP1Miravalle · Guadalajara · 1956Chapala water via the aqueduct and the old system. Supplies more than 45 % of the metropolitan area, about 2.1 million people. The seven zones under rotating cuts depend on it.
PP2Las Huertas · Tlaquepaque · 1990Chapala water.
PP3San Gaspar · Tonalá · 1991Water from Calderón and the El Zapotillo system. Designed for 3.0 m³/s; runs at about 2.3 m³/s.
PP4Toluquilla · Tlaquepaque · 2006Well water. Averaged 375 L/s in 2020–2022, against a design capacity of 1,000 L/s. Not shown on the map because we do not have a verified location.
PP5Los Agaves · Tlajomulco · 2024Chapala water via the La Calera system. The only one designed to the current drinking-water standard.
Wells that supply some neighborhoods directly do not pass through these plants. And here the map stops: storage tanks and the distribution network are not public information. To find out where the water at a specific address comes from, you have to check with SIAPA.
PP2 and PP3 are located using INEGI place names; Miravalle and Los Agaves approximately. Years are when operations began. No public source states which neighborhoods each plant supplies, except the seven Miravalle zones under rotating cuts.
Downstream of the Corona dam, the Santiago passes through El Salto and Juanacatlán. There another story unfolded: that of a river that for decades received the waste of industry and of the city.
1893El Salto de Juanacatlán
The power of the river
In 1893, the Compañía de Luz y Fuerza Motriz Eléctrica de Guadalajara obtained a concession to build a hydroelectric plant at the Salto de Juanacatlán waterfall and use up to 5 m³/s of the river. The power ran the Río Grande textile mill and Guadalajara's street lighting.
The waterfall, about 20 meters high, was a famous outing. More hydroelectric plants were built downstream: Puente Grande began operating in 1912, and INEGI charts still show the Colimilla, Intermedia and Las Juntas plants in the canyon. The river provided work and energy long before it became an environmental problem.
1896 · Atequiza, another early use of the Santiago
Upstream, the Atequiza hacienda obtained confirmation of its rights to the Santiago in 1896: 3,500 liters per second for irrigation and motive power, taken through a diversion dam opposite the village of Atotonilquillo. It expanded dams and canals that drove a wheat mill, a distillery, a brickworks and a hydroelectric plant. These were works of the Porfiriato era, separate from the 1956 urban system, but they show that the river was harnessed for production long before it supplied the city.
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Dates for the first factories vary by source. Rodríguez and Cota (2006) place a spinning mill in 1866, the Río Grande mill in 1876 and the hydroelectric plant in 1892; Lezama and Téllez (2015) date the concession to 1893. The waterfall's location is INEGI's (chart F13D66).
In 1967 the Guadalajara Industrial Park opened in El Salto, part of a federal industrial-park program. IBM arrived in the 1970s, followed by electronics, chemical, petrochemical, tire, plastics and food plants.
El Salto became one of the industrial hubs of western Mexico, and growth continued: INEGI's business directory (DENUE) went from 595 manufacturing establishments in the municipality in 2010 to 1,103 in 2025. Almost nine of every ten are in the El Ahogado basin.
595
921
939
1,103
2010201520202025
Manufacturing establishments (NAICS 31–33) in El Salto. Author's analysis of DENUE (INEGI). The map points are the 2025 ones.
The city was growing too, and with it its wastewater. The large treatment plants would arrive more than four decades after the first industrial park.
Academic researchOfficial data · author's analysis
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That a company operates in the corridor does not prove it polluted the river. Attributing a discharge requires permits, monitoring and case files for each company. DENUE counts establishments, not their size or emissions, and its coverage changed between editions: part of the increase may reflect better recording.
The El Ahogado stream drains a basin of about 172 km² in the south of the metropolis, between Tlaquepaque, Tlajomulco and El Salto. It collects runoff and wastewater and flows into the Santiago just above the waterfall. Using CEA monitoring data from 2009 to 2012, a study rated the river's water quality as “poor” at every site along that stretch and singled out El Ahogado as one of the tributaries that degrade it most.
Official emissions data point the same way. Of 68 establishments in El Salto that filed reports with the Pollutant Release and Transfer Register (RETC) between 2004 and 2024, 33 declared releases to water in at least one year, and 30 of them are in the El Ahogado basin (red points).
The intake is upstream
The Corona dam is about 15 km in a straight line (more than 20 km along the river) upstream of El Salto. Pollution at the waterfall does not flow back to Corona. The two stories meet somewhere else: on the edge of the El Ahogado basin, where the Las Pintas canal runs. We will see it in Part III.
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The quality index (CCME WQI) ranged from 11.96 to 37.23 out of 100 within the environmental fragility polygon (27 sampling campaigns, about 13,800 data points). An overall index does not say which substance or source causes the deterioration. The RETC is an annual self-report by companies: it shows there were releases to water, not whether they exceeded the standard (NOM-001 assesses concentrations) or caused harm. That is why the atlas does not name companies. The basin outline (172 km²) is an INEGI SIATL delineation made upstream of the El Ahogado outlet; the stream line comes from the author's GeoPackage and INEGI charts.
On January 25, 2008, Miguel Ángel López Rocha, a boy from El Salto, fell into the Santiago River. He died on February 13. According to the medical opinion of Mexico's National Human Rights Commission (CNDH), the cause was multiple organ failure from acute, severe arsenic poisoning.
In 2010, the CNDH concluded that the National Water Commission (Conagua) had violated the rights to a healthy environment, to health and to life by failing to clean up the river. His death became a symbol for the communities of El Salto and Juanacatlán.
Official document
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The case documents the risk of direct contact with the river water. It is not evidence about the quality of the city's drinking water, which is taken from other points.
2009The Jalisco Human Rights Commission (CEDHJ) issues Recommendation 1/2009 to the governor, the CEA, SIAPA and 14 municipal governments over the pollution of the Santiago in El Salto and Juanacatlán.
2010The CNDH issues Recommendation 12/2010 over the case of Miguel Ángel.
2020The Inter-American Commission on Human Rights (IACHR) grants precautionary measures (Resolution 7/2020) to people living within 5 km of the river in El Salto and Juanacatlán, and to communities in Poncitlán. It notes that the treatment plants are not suited to industrial pollution.
2022In Recommendation 134/2022, the CNDH reports more than a thousand toxic substances detected in studies, arsenic and lead above the limit in some areas, and industries discharging with no or deficient treatment.
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A human rights recommendation is not a criminal ruling and does not by itself identify private parties as responsible. The 5 km band on the map is illustrative: a zone around the riverbed within El Salto and Juanacatlán, not an official polygon.
The metropolis's wastewater leaves by two paths, and both end in the Santiago River, downstream of the Corona intake: from the south, through the El Ahogado stream; from the center and north, toward the canyon. Until early 2012, according to SIAPA, less than 1 % of the 8.3 m³/s of wastewater the city generated was treated.
In 2012 the El Ahogado plant began operating; it treats about a fifth of household discharges. Agua Prieta followed in 2014; the CEA reports that it treats 6.7 m³/s in the rainy season and 5.0 in the dry season. It does not capture the basins on the city's east side because a collector tunnel is missing. In 2020, the IACHR noted that these plants are not suited to industrial pollution.
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The dotted arrow for the center and north sewage is schematic: there is no public layer of collectors. Because these discharges reach the Santiago downstream of Corona, they do not enter the old system; the 2026 problem comes from discharges into the canals. A plant being in operation does not guarantee it treats all the sewage or that its effluent meets the standard.
This year, pollution stopped being a problem “of the river”: it reached the taps of hundreds of neighborhoods.
2020–2026Las Pintas canal and dam
Where the two stories meet
The Las Pintas canal, the last open stretch of the old system, runs along the western and southern edge of the El Ahogado basin, between Tlajomulco, El Salto and Tlaquepaque, an area that has grown enormously in recent decades. The Las Pintas dam sits at the head of that basin, where the El Ahogado stream begins. The water on its way to be treated for drinking passes right through the area that drains the city's southern wastewater.
In 2026, SIAPA told the CEDHJ that sewer lines discharge untreated wastewater into the canal at seven points in Tlajomulco, with additional inflows from Tlaquepaque into the Seco stream and the canal. The Commission had already issued a recommendation in 2022 over poor water quality in the city, which by 2026 had still not been met.
Voices from El Salto
“We told them it would reach them, but they didn't believe us,” recalls Enrique, who used to fish in the Santiago. After the October 11 march, the collective Un Salto de Vida put it this way: “for decades we have denounced this same toxic pollution that has now reached you.”
Testimony and public statement, not measurements. The polluted Santiago at El Salto and the canal are separate water paths; what they share is the territory. Quotes translated from Spanish.
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According to the SIATL delineation, the canal lies just outside the El Ahogado basin, on its watershed divide: it runs along the boundary, not inside it. That is why the canal can receive discharges from both sides of the edge. INEGI records two dams named Las Pintas; the one in the old system is in Tlaquepaque, next to the canal.
Since 2016, residents of various neighborhoods have reported cloudy water with sediment. In 2020, an El Informador investigation documented complaints of sewage-tainted water in 140 neighborhoods, and the CEDHJ opened a case that led to Recommendation 10/2022. In 2025, SIAPA detected coliform bacteria in the network at least 15 times, with a peak of 99 per 100 ml in September.
On March 10, 2026, the CEDHJ opened a new investigation on its own initiative. By July it had identified some 600 neighborhoods with contaminated water, while the state government acknowledged about 200. That year it received 130 complaints against SIAPA, filed by 1,245 people.
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The CEDHJ's and the government's neighborhood counts do not match. According to the CEDHJ itself, the CEA had no sampling of the canal, the dam or the Miravalle plant, and its laboratories are not certified for those analyses.
The CEDHJ addressed a recommendation to nine authorities: SIAPA, the CEA, the state environmental attorney's office (Proepa), the state health-risk agency (Coprisjal), the state ministries of Integrated Water Management, Health and Environment, and the municipal governments of Tlaquepaque and El Salto, for violating the rights to water, to a healthy environment and to health.
It documented that part of the Las Pintas dam, with a capacity of 275,000 m³ and under concession to SIAPA, had been filled in and built on, including a brickworks, and that at least four construction permits had been issued in the area. It also found that the CEA had no sampling of the canal, the dam or Miravalle, and that CIATEJ monitoring in 2021 and 2022 in the El Ahogado basin and the Las Pintas stream found heavy metals, pesticides and fecal bacteria.
In July, work began to modernize the Miravalle treatment plant, in operation since 1956: a new 2 m³/s treatment train and the conversion of the existing units. The first stage costs 2.5 billion pesos; the full project is estimated at 6.563 billion.
SIAPA also installed the first of 40 mobile water-treatment plants, each able to fill up to 1,500 large water jugs a day, as part of emergency actions worth about 100 million pesos. Major improvements in water quality were announced for February 2027.
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The total cost of the modernization is a CEA estimate, not a final budget. On October 21 the governor spoke of about 7.5 billion pesos for the first stage of expanding and modernizing PP1, a different figure from the CEA's project sheet. The July plan addressed water quality without yet shutting down the old system.
Governor Pablo Lemus acknowledged the crisis and announced that water from the Las Pintas dam and the old system would no longer be used. That route supplies up to 2.5 m³/s, around 19 % of the city's water according to estimates based on SIAPA data.
The measure would last about six months, while a bypass aqueduct is built at La Calera, the Miravalle plant is expanded, and the dam and canal are cleaned up. As a long-term solution, the government proposed a replacement Chapala–Guadalajara aqueduct, with an estimated two-year timeline and Conagua's approval.
The debate over the replacement aqueduct
It would cost 11.922 billion pesos under a CMRO scheme (construction, maintenance, rehabilitation and operation): a private company would build and run it, and the CEA would pay it for up to 25 years. The government says it is neither debt nor privatization and that rates will not rise. At the October 11 march, protesters chanted “water is a right that cannot be privatized.” On October 21 a federal contribution was announced; the bill is still before the state Congress.
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The 19 % is an estimate by water specialist Juan Pablo Macías based on SIAPA data, published by El Informador. The old system's actual flow varies; 2.5 m³/s is the maximum reported.
SIAPA began rotating service (tandeo) in 627 neighborhoods of Guadalajara, Tlaquepaque, Tonalá and Zapopan, divided into seven zones that depend on the Miravalle plant. Supply periods alternate, with low pressure and interruptions; water trucks and 10,000-liter tanks are placed at strategic points. The rotation will last until March 2027.
Specialists cited by El Informador estimated that some 950,000 people would feel the effects.
This map does not draw the rotation zones: there are no downloadable official polygons. “627 neighborhoods” is the scheduled universe, not a measurement of cuts at each address, and the 950,000 people are a specialists' estimate, not an official figure.
In March, SIAPA acknowledged at least 10 irregular discharges into the old system. After a joint review with Conagua, the CEA and the municipalities, by October 13 there were 72 points identified, 42 of them plugged. According to SIAPA, the largest discharges arrive via the Seco stream, which flows into the canal, from informal settlements whose systems are “practically overflowing into the channel.”
On October 21 the government announced 500 million pesos to repair sewer collectors in Tlajomulco and Tlaquepaque and send that water to the El Ahogado treatment plant, dredge the Las Pintas and La Calera dams, and work on the Seco stream. The goal is to restart the old system from December; the La Calera bypass and the new Miravalle module would follow between March and April 2027.
Atequiza is also on the discharge route
The old system is an open canal of about 92.5 km that passes through the Atequiza canal in Ixtlahuacán de los Membrillos. Wastewater discharges were detected “along its route.” The figures refer to the whole old system: it has not been published how many are in Atequiza or who is responsible for them.
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“Plugged” does not mean verified by lab analysis. The location and type of each discharge have not been published, nor how many are household versus industrial. According to Conagua, only 20 penalties have been imposed since 2019 for irregular discharges into bodies of water in Jalisco.
The crisis has no single cause. It combines an open route that crosses urban and industrial areas, uncontrolled discharges, an encroached dam, a treatment plant with a 70-year-old process, and decades of recommendations left unmet.
Solving it requires protecting the source, monitoring and penalizing discharges, and publishing data on the quality of the water that reaches homes.
The same story, organized so you can find an answer quickly. Each section has its own link.
The system in one diagram
On the left, the water entering the city, drawn to scale by flow. On the right, the used water leaving it. The red line marks the 2026 failure: wastewater flowing back into the drinking-water route.
Swipe the diagram to the right →
Inflow: 2017–2022 average (McCulligh 2024); the sum (10.2) differs from the reported total (10.1) because of rounding. The old system's maximum (2.5 m³/s) is a 2026 figure. Outflow: not to scale, because there is no recent public figure for how much wastewater is treated; until 2012 the city generated 8.3 m³/s and treated less than 1 % (McCulligh 2018). Agua Prieta's capacity is the CEA's figure for the rainy season.
Where does the water come from?
Guadalajara gets water from four sources. The main one is Lake Chapala, which arrives by two routes: the Chapala–Guadalajara aqueduct (1991), a closed pipe that takes water straight from the lake, and the old system (1956), which uses the Santiago River and the open Atequiza and Las Pintas canals.
The other sources are wells and springs, the Calderón dam and, since 2024, the El Zapotillo system, which brings water from the Verde River to Calderón.
The Lerma–Santiago hydrological region (RH12). The box is the map area.
Sources of the water distributed by SIAPA
Source
How it arrives
m³/s
% 2026
Since
Lake Chapala
Closed aqueduct and old system (river and open canals)
6.3
63
1956 · 1991
↳ old system
Ocotlán → Santiago River → Corona → Atequiza → La Calera → Las Pintas → Miravalle
up to 2.5
19
1956
Wells and springs
Directly into the network or to plants such as Toluquilla
2.8
20
since the 16th century
Calderón dam
31 km aqueduct to San Gaspar
1.1
17
1991
El Zapotillo
Verde River → El Salto → La Red → Calderón; running at 45 % (2026)
—
in Calderón
2024
Average flows 2017–2022 (McCulligh 2024), except the old system's maximum (Jalisco government, 2026). El Zapotillo is not included in that average. 2026 percentages from El Informador (Oct 17, 2026): Chapala 63 % (44 % via the aqueduct and 19 % via the old system), Calderón 17 %, wells 19 % and springs 1 %.
The treatment plants
The raw water's journey ends at a drinking-water treatment plant, where it is cleaned and disinfected. Then it flows into tanks and SIAPA's pipe network. That network is not public information, so from the outside it is impossible to know which neighborhoods each plant supplies, except the seven Miravalle zones under rotating cuts.
Drinking-water treatment plants in the metropolitan area
Plant
Municipality
Water it receives
Facts
PP1 Miravalle
Guadalajara
Chapala (aqueduct and old system)
Since 1956. Supplies more than 45 % of the metropolitan area (about 2.1 million people). Modernization under way: first stage of 2.5 billion pesos.
PP2 Las Huertas
Tlaquepaque
Chapala
Since 1990.
PP3 San Gaspar
Tonalá
Calderón and El Zapotillo
Since 1991. Design 3.0 m³/s; runs at about 2.3 m³/s.
PP4 Toluquilla
Tlaquepaque
Wells
Since 2006. 375 L/s on average (2020–2022) against a design capacity of 1,000 L/s.
PP5 Los Agaves
Tlajomulco
Chapala, via the La Calera system
Since November 2024. The only one designed to the current drinking-water standard.
Sources: CEA (project sheets an-0021 and an-0024); McCulligh (2024); El Informador (Oct 15, 2026).
Why is the tap water contaminated?
What had been documented as of October 21, 2026 points to the open route of the old system:
The water travels in the open. Part of Chapala's water travels tens of kilometers along the Santiago River and open canals before reaching Miravalle. At Ocotlán, the Santiago also receives the Zula River, with agro-industrial discharges from Los Altos.
The canals ended up surrounded by city. The Las Pintas canal runs along the edge of the El Ahogado basin, a heavily urbanized and industrial area. SIAPA reported 72 discharge points in the old system, and the CEDHJ documented sewer lines dumping untreated wastewater into the canal and part of the dam filled in and built on.
The treatment plant can't keep up. Miravalle has operated since 1956 with a process that, according to specialists cited by El Informador, is no longer adequate; of the five plants, only the new PP5 was designed to the current drinking-water standard. Treating water for drinking is not the same as treating wastewater.
The network can make it worse. In 2025, SIAPA detected coliform bacteria in the network at least 15 times. More than 70 % of the pipes are over 30 years old, and 25 to 30 % of the water is lost. A University of Guadalajara academic warns that, at low pressure, water from leaking sewers can seep into the network: it is a risk, not a confirmed finding. No official results have been published that would show at which point along the way the water gets dirty.
The Santiago passes through El Salto and Juanacatlán downstream of the Corona intake. There it receives the El Ahogado stream, which drains the south of the metropolis, and further on the sewage from the city's center and north. Until 2012 almost none of that water was treated; since 2012 and 2014 the El Ahogado and Agua Prieta plants have operated, which according to the IACHR are not suited to industrial pollution.
The river's pollution at El Salto does not flow back to the Corona intake, so it does not directly explain the dirty water in homes. But it is the same underlying story: urban and industrial growth with poorly monitored discharges. Three human rights bodies have called out the authorities: the CEDHJ (2009), the CNDH (2010 and 2022) and the IACHR (2020).
1,103manufacturing establishments in El Salto (DENUE 2025), up from 595 in 2010
30 of 33establishments that reported releases to water to the RETC are in the El Ahogado basin
1,000+toxic substances detected in studies of the river, according to the CNDH (2022)
The 2026 crisis, in brief
Mar 10The CEDHJ opens an investigation on its own initiative into cloudy, foul-smelling water in several neighborhoods.
Apr 30CEDHJ Recommendation 10/2026: part of the Las Pintas dam was filled in and built on, and there is no official sampling of the canal, the dam or Miravalle.
JulEmergency plan: 40 mobile treatment plants and the start of Miravalle's modernization (first stage: 2.5 billion pesos according to the CEA; in October the governor spoke of about 7.5 billion).
Oct 6The old system, which supplies up to 2.5 m³/s, is suspended.
Oct 11March for clean water from La Minerva to Casa Jalisco; 39 people detained. On October 13 the governor acknowledges excessive use of force and all are released (El Informador, Oct 12; Oct 13).
Oct 13SIAPA reports 72 discharge points identified in the old system; 42 had been plugged in an earlier phase.
Oct 15Rotating cuts begin in 627 neighborhoods across seven Miravalle zones; the first stage will last until March 2027.
Oct 21500 million pesos announced to clean up the canal (restart planned from December) and a federal contribution for the replacement aqueduct.
What we know and what we don't
Documented
The old system takes water from the Santiago at Corona, upstream of El Salto, and carries it through open canals to Miravalle.CEA; McCulligh 2024
The Santiago as it passes El Salto and Juanacatlán is severely polluted.CEDHJ 2009; CNDH 2010 and 2022; IACHR 2020
The metropolis's sewage flows into the Santiago downstream of Corona. Until 2012 almost none of it was treated.McCulligh 2018
Part of the Las Pintas dam was filled in and built on, and the CEA has no sampling of the canal, the dam or Miravalle.CEDHJ 2026
Reported, without complete data
72 discharge points in the old system, 42 plugged. There is no public list or classification by type.SIAPA, Oct 13, 2026
Establishments without an environmental license next to the dam. There is no public inventory of industrial discharges.CEDHJ 2026
Some 600 neighborhoods with contaminated water according to the CEDHJ; the government acknowledges about 200.El Informador, Jul 8, 2026
Since 2019, Conagua has imposed only 20 penalties for irregular discharges into bodies of water in Jalisco.El Informador, Mar 14, 2026
Open questions
Which contaminants reached household water, and at what concentration?
Who penalizes the discharges, and with what case files? How much is industrial and how much urban?
How much pollution does the Zula River contribute to the water diverted at Corona?
With what quality controls will the old system restart?
What will happen to the Las Pintas dam, and will Recommendation 10/2026 be met?
Frequently asked questions
Is it safe to drink tap water?
No official laboratory results have been published that would allow a reliable answer for each neighborhood. In April 2026 the CEDHJ asked for analyses from external laboratories and chlorine levels to be published. If the water comes out with color, odor or sediment, do not use it for drinking or cooking. Boiling kills microbes but does not remove metals or chemicals. Coprisjal told the CEDHJ that inspections of SIAPA's plants found results within the standard, but there is no public sampling of the network in each neighborhood. SIAPA has installed mobile treatment plants with free water jugs.
Where does my neighborhood's water come from?
There is no public map of which plant supplies each neighborhood. If your neighborhood is in one of the seven zones under rotating cuts, its water comes from the Miravalle plant. You can look up your address on SIAPA's website (in Spanish).
Why does it smell like sewage?
The official explanation is that wastewater was reaching the Las Pintas canal through irregular discharges, and the Miravalle plant, with an old process, cannot clean that mix. That is why the old system was suspended on October 6, 2026.
Does El Salto's pollution reach my home?
Not directly. The Santiago becomes polluted at El Salto, downstream of the Corona dam where the old system's water is taken, and water does not flow backward. The 2026 problem comes from discharges into the canals, not from the river at El Salto. The two share an underlying cause: uncontrolled discharges in an urban and industrial area.
When will the rotating cuts end?
SIAPA announced that the rotation will last until March 2027. The old system will restart once the canal and dam are stabilized, and with the Miravalle and La Calera works the government expects to end the rotation.
Why not shut down the old system for good?
Because it supplies up to 2.5 m³/s, around 19 % of the city's water. The government proposed a closed replacement Chapala–Guadalajara aqueduct, with an estimated two-year timeline, and in the meantime a bypass aqueduct at La Calera.
Are El Salto's companies to blame?
Public data show many industries and reports of releases to water in the El Ahogado basin, but that does not prove a specific company contaminated the drinking water. Assigning responsibility requires the discharges to be identified with their location, origin and lab analysis. That list has not been published.
Who is responsible for what?
Main responsibilities
Institution
Its role
SIAPA
Treating and distributing drinking water and operating the sewer system in its member municipalities.
CEA Jalisco
State water infrastructure, such as the old system, La Calera and the wastewater treatment plants.
Conagua
National waters: concessions for the lake and river, and permits for discharges into bodies of water (NOM-001).
Profepa and Proepa
Inspecting and penalizing companies (federal and state, depending on the activity).
Municipalities
Land use and discharges into the municipal sewer, together with the water utility.
Coprisjal and Jalisco Health
Monitoring the sanitary quality of drinking water and public health.
General summary of responsibilities. CEDHJ Recommendation 10/2026 assigns specific tasks to each of these institutions.
Glossary
Drinking-water treatment (potabilizar)
Cleaning and disinfecting lake, dam or well water so it is safe to drink. Plants such as Miravalle do this.
Wastewater treatment
Cleaning used water (sewage) before returning it to a river. Plants such as El Ahogado or Agua Prieta do this.
m³/s
Cubic meters per second: a thousand liters every second. 1 m³/s fills an Olympic pool in about 40 minutes.
Old system (sistema antiguo)
The 1956 route that carries Chapala water through the Santiago River and the open Atequiza and Las Pintas canals to Miravalle.
Diversion dam
A dam that stores little water: it is used to divert part of a river into a canal. Corona is one.
Basin
The land whose rain and runoff end up in the same river or stream. El Ahogado's covers about 172 km².
Irregular discharge
Wastewater released where it should not be or without a permit, for example into a drinking-water canal.
Tandeo
Rotating service: zones take turns with days or periods of low pressure or no water.
RETC
Pollutant Release and Transfer Register (SEMARNAT). Companies report each year what they release to air, water and soil.
NOM-001-SEMARNAT-2021
The Mexican standard that sets pollutant limits for wastewater discharges into national rivers, lakes and other bodies of water.
Residual chlorine
Chlorine still in the water when it reaches the tap. It shows the water is still protected against microbes.
Colonia
A neighborhood, the basic unit used by SIAPA and the authorities to report service and complaints.
Full timeline
Year
Event
Source
1893
Concession for the hydroelectric plant at the Salto de Juanacatlán.
Lezama and Téllez 2015
1896
The Atequiza hacienda obtains confirmation of 3,500 L/s from the Santiago River for irrigation and motive power.
Pacheco Urista 2012, 2018
1912
The Puente Grande hydroelectric plant begins operating.
Lezama and Téllez 2015
1956
The old Chapala–Guadalajara system begins operating (4,000 L/s permit).
McCulligh 2024; CEA
1967
The Guadalajara Industrial Park opens in El Salto.
Rodríguez and Cota 2006
1978
SIAPA is created.
McCulligh 2024
1979
The city receives 7.7 m³/s; 81 % from Chapala.
Flores Berrones c. 1987
1991
The Chapala–Guadalajara aqueduct (42.6 km, 7.5 m³/s) and the Calderón dam with its aqueduct to San Gaspar are completed.
McCulligh 2024
2008
Miguel Ángel López Rocha dies after falling into the Santiago.
CNDH 2010
2009
CEDHJ Recommendation 1/2009 on the Santiago.
CEDHJ 2009
2010
CNDH Recommendation 12/2010.
CNDH 2010
2012
The El Ahogado wastewater treatment plant begins operating. Before that, less than 1 % of the sewage was treated.
McCulligh 2018
2014
The Agua Prieta wastewater treatment plant begins operating.
CEA
2016
Recurring reports of cloudy, sediment-laden water in the city begin.
El Informador 2026
2020
IACHR precautionary measures (Resolution 7/2020). The CEDHJ opens a case over sewage-tainted water in 140 neighborhoods.
IACHR 2020; El Informador 2026
2021
Calderón stops supplying water from March to August because it ran dry.
McCulligh 2024
2022
CEDHJ Recommendation 10/2022 over poor water quality (February 14). CNDH Recommendation 134/2022 on the Santiago.
El Informador 2026; CNDH 2022
2024
The El Zapotillo dam is completed (August) and the PP5 treatment plant opens (November).
El Informador 2026
2026
CEDHJ investigation, Recommendation 10/2026, shutdown of the old system, the October 11 march, rotating cuts in 627 neighborhoods, 72 discharge points identified and a 500-million-peso cleanup plan.
See the story
Updates
Oct 24, 2026 English version published.
Oct 22, 2026 Added the Zula River, the cleanup plan and the replacement-aqueduct debate, the October 11 march, the state of SIAPA's network and voices from El Salto. Information current to October 21.
Oct 22, 2026 Added notes on the Atequiza canal: its role in the old system, its history since 1896 and its place in the 2026 discharge review.
Oct 21, 2026 Added the reference section, the explore map, the system diagram and the chapter on the July emergency plan. Information current to October 20.
Oct 21, 2026 Press sources replaced with El Informador and official documents; figures corrected accordingly.
McCulligh, C. (2024). El cambiante territorio hidrosocial del Área Metropolitana de Guadalajara, México: las huellas de los conflictos. Revista de El Colegio de San Luis, 14(25), e1568. doi.org/10.21696/rcsl142520241568
McCulligh, C. (c. 2018). Los retos políticos y sociales del saneamiento de aguas residuales municipales: casos de la Cuenca Alta del río Santiago. estudiosdeldesarrollo.mx
Muñoz Ríos, M. D. (2026). Doctoral research database on El Salto: industrial DENUE 2010–2025 (INEGI) and RETC 2004–2024 (SEMARNAT), georeferenced and classified by basin. Author's own compilation, CUCSH-UdeG.
Flores Berrones, R. (c. 1987). Acueducto Chapala–Guadalajara. SARH. Archive of Tecnología y Ciencias del Agua. revistatyca.org.mx
Lezama Escalante, C., & Téllez Lozano, V. M. (2015). La industria hidroeléctrica del río Santiago y su impacto socioambiental en el occidente de México. Diversa, 2(1), 35–52. diversae.lagos.udg.mx
Rodríguez Bautista, J. J., & Cota Yáñez, M. R. (2006). Desarrollo de el Parque Industrial El Salto, Jalisco. Cadernos PROLAM/USP, 5(2), 83–104. revistas.usp.br
Pacheco Urista, L. Y. (2012). De tierra, agua y tuercas. La presencia industrial en la hacienda de Atequiza durante el Porfiriato y sus huellas al siglo XXI. Boletín de Monumentos Históricos, 3rd series, (25), 127–146. INAH. revistas.inah.gob.mx
Pacheco Urista, L. Y. (2018). Haciendas, industrias y lacustres en disputa: conflictos y aprovechamiento hidráulico en el valle de Atequiza, Jalisco, a finales del siglo XIX. Punto CUNorte, (6), 149–180. University of Guadalajara. cunorte.udg.mx
De Anda-Sánchez, J., Olvera-Vargas, L. A., & Lugo-Melchor, O. (2022). Diagnóstico de calidad del agua en los ríos Santiago y Zula y sus afluentes. CIATEJ for SEMADET and FONNOR, Estrategia Integral para la Recuperación del Río Santiago. riosantiago.jalisco.gob.mx
Contreras-Dávila, C. A. et al. (2013). Calidad del agua del río Santiago dentro del polígono de fragilidad ambiental en la cuenca El Ahogado. IWA-México YWP. riosantiago.jalisco.gob.mx
Comisión Estatal del Agua de Jalisco. Conservación del Sistema Antiguo Chapala–Guadalajara (project sheet an-0019). planintegraldelagua.jalisco.gob.mx
Comisión Estatal del Agua de Jalisco. Sistema de abastecimiento La Calera – PP5 (project sheet an-0014). planintegraldelagua.jalisco.gob.mx
Comisión Estatal del Agua de Jalisco. Modernización de la Planta Potabilizadora No. 1 Miravalle (project sheet an-0021). planintegraldelagua.jalisco.gob.mx
Comisión Estatal del Agua de Jalisco. Planta Potabilizadora No. 3 San Gaspar (project sheet an-0024). planintegraldelagua.jalisco.gob.mx
CNDH (2010). Recomendación 12/2010, March 2. cndh.org.mx
IACHR / CIDH (2020). Resolución 7/2020, MC 708-19, February 5. oas.org
CNDH (2022). Comunicado DGDDH/218/2022 sobre la Recomendación 134/2022. cndh.org.mx
CEDHJ (2026). Recomendación 10/2026, April 30. cedhj.org.mx
Government
SIAPA & Gobierno de Jalisco. Agua limpia para Jalisco: consulta de rotación del servicio por domicilio [address lookup for rotating service]. rotaciondeserviciosiapa.jalisco.gob.mx
Testimony and public statements
El Universal (2026). Agua sucia en Guadalajara, la crisis que se advirtió hace 20 años [video]. youtube.com
Un Salto de Vida (2026, October). Public statement to the people of the Guadalajara metropolitan area after the October 11 march [in Spanish].
Press · El Informador (in Spanish)
El Informador (2026, March 23). Agua sucia en la ZMG: CEDHJ abre investigación por el líquido turbio del SIAPA. informador.mx
González Hernández, O. (2026, July 8). Suman 600 colonias en Guadalajara que reciben agua contaminada; problemática data de 2019, reconoce CEDHJ. El Informador. informador.mx
González Hernández, O. (2026, July 16). SIAPA: llega la primera planta potabilizadora móvil a El Sauz; proyectan 40 en el AMG. El Informador. informador.mx
Elizondo, E. A. (2026, October 6). SIAPA en Guadalajara, Jalisco: Lemus anuncia cortes de agua por seis meses. El Informador. informador.mx
Hernández, M. (2026, October 6). Cortes de agua del SIAPA: ¿cuánto tiempo durarán y cómo serán los tandeos en la ZMG? El Informador. informador.mx
Hernández, M. (2026, October 6). Cortes de agua en ZMG: estiman hasta 950 mil habitantes afectados por los tandeos. El Informador. informador.mx
El Informador (2026, October 12). Cortes de agua del SIAPA: lista completa de las 627 colonias de la ZMG que entran en la rotación de agua limpia. informador.mx
El Informador (2026, March 14). Siapa: autoridades toleran contaminación del agua en Guadalajara. informador.mx
Hernández, M. (2026, October 8). Descartan endeudamiento en proyecto de segundo acueducto Chapala-GDL. El Informador. informador.mx
Hernández, M. (2026, October 8). SIAPA reconoce dificultades en la vigilancia del Sistema Antiguo Chapala-GDL. El Informador. informador.mx
El Informador (2026, October 12). Manifestaciones: ciudadanos exigen agua limpia. informador.mx
González Hernández, O. (2026, October 13). Lemus reconoce abusos durante manifestación en Casa Jalisco; liberan a todos los detenidos. El Informador. informador.mx
El Informador (2026, October 13). Cronología de la crisis de agua en Guadalajara, así empezó. informador.mx
Hernández, M. (2026, October 13). Saneamiento de Las Pintas permitirá identificar descargas irregulares, según autoridades. El Informador. informador.mx
El Informador (2026, October 13). Agua: calidad y abastecimiento, los desafíos hídricos de la ZMG. informador.mx
El Informador (2026, October 15). Hoy discuten en el Congreso de Jalisco financiamiento para segundo acueducto Chapala-Guadalajara. informador.mx
El Informador (2026, October 15). SIAPA: cuatro plantas potabilizadoras operan con tecnología rezagada. informador.mx
El Informador (2026, October 16). Agua en Guadalajara: la red del SIAPA es antigua y provoca fallas. informador.mx
Solano, G. (2026, October 17). ¿Cuáles son las principales fuentes de agua en Guadalajara? El Informador. informador.mx
Álvarez Gutiérrez, Ó. E. (2026, October 18). Chapala aporta 6 de cada 10 litros: así se distribuye el agua en Guadalajara ante la rotación. El Informador. informador.mx
Solano, G. (2026, October 21). Gobierno de Jalisco anuncia inversión para sanear el canal de Las Pintas. El Informador. informador.mx
Hernández, M. (2026, October 21). Agradecemos la inversión federal en las obras de infraestructura: Pablo Lemus. El Informador. informador.mx
Map layers
Atequiza and Las Pintas canals, Las Pintas dam: INEGI 1:50,000 topographic charts F13D65, F13D66 and F13D76.
Unnamed aqueducts from the same INEGI charts, identified by route as the Chapala–Guadalajara aqueduct and the Calderón–San Gaspar corridor.
Dotted stretches: schematics joining known points. They are not surveyed pipes.
Santiago River, El Ahogado stream and stream network: the author's GeoPackage (MAPA_HIDROLOGICO_EL_SALTO) and INEGI named watercourses.
El Ahogado basin (172 km²): INEGI SIATL delineation, included in the author's GeoPackage.
Dams, treatment plants PP2 and PP3, hydroelectric plants and canyon: INEGI hydrological place names from the author's GeoPackage. Miravalle, PP5 and the aqueduct intake remain approximate.
Shaded relief: 30 m SRTM (NASA/USGS, via Google Earth Engine), resampled to 60 m. Author's processing.
Lake Chapala: INEGI chart F13D76 for its northwestern part and Natural Earth 1:10 m for the rest of the shoreline.
Municipal boundaries: INEGI, Marco Geoestadístico 2022 (via PhantomInsights/mexico-geojson), simplified.
→Arrows: direction of flow. On rivers and canals they follow the slope; for the center and north sewage they are schematic.
Manufacturing establishments in El Salto (DENUE 2025, INEGI) and establishments reporting releases to water (RETC, SEMARNAT, 2004–2024): author's analysis. Shown without names.
5 km band: illustrative zone around the riverbed in El Salto and Juanacatlán, based on IACHR Resolution 7/2020.
Limitations
This atlas reconstructs a story from public documents. It does not measure water quality, it is not an inventory of discharges and it does not attribute pollution to specific companies. The locations of treatment plants and of the aqueduct intake are approximate; each point states its precision. The October 2026 figures are reports from that moment and may change. The English text is a translation of the Spanish edition; source titles and quotations are kept in or translated from the original Spanish. Outside this platform, the map uses Esri's gray basemap as its background or, if that is unavailable, OpenStreetMap.
How to cite
Muñoz Ríos, M. D. (2026). From lake to tap: A water atlas of Guadalajara [Interactive atlas; English edition of Del lago a la llave]. Information current to October 21, 2026.