Apr 252016
 

Cuatro Ciénegas (“Four Marshes”) is a city and municipality in the northern border state of Coahuila. Founded in 1800, it has some historical significance, since it was the birthplace of Venustiano Carranza, Mexico’s president from 1915 to 1920.

The natural nearby “marshes” are highly unusual. Situated in an arid region (part of the Chihuahuan desert), they include several natural springs that feed more than 200 small ponds and wetlands. Some of the water supporting these unique wetlands, which cover an area of 84,400 hectares, is believed to be more than 200 million years old. The wetlands are an integral part of the UNESCO-designated Cuatro Ciénegas biosphere reserve. The reserve is home to several endemic organisms, including microorganisms such as cyanobacteria that historically helped produce oxygen for the Earth’s atmosphere. The area is considered “a living laboratory of evolution and the origin of life”.

Cuatro Ciénegas. Credit: Nancy T. Wilson (MexConnect)

Cuatro Ciénegas. Credit: Nancy T. Wilson (MexConnect.com)

Human activities in the surrounding area have led to severe water stress on the Cuatro Ciénegas marshes. The basin’s average natural recharge rate (replenishment rate) is about  25 million cubic meters a year, but the average yearly extraction rate, almost all for agricultural use, is close to 49 million cubic meters.

Water stress may be exacerbated in coming years by climate change, which may reduce rainfall while simultaneously increasing evapotranspiration.

Scientists have also identified five particular exotic (introduced) species that pose a significant risk to the long-term quality of the Cuatro Ciénegas wetlands. Whether naturally or deliberately introduced, these five species – African jewelfish, blue tilapia, giant cane (giant reed), Guatemalan fir and tamarisk (salt cedar) – threaten to displace endemic species and change natural nutrient flows and food chains. Guatemalan fir and tamarisk soak up water as they grow, further drying out the marshes (though, eventually, when little water is left, they will die off). The blue tilapia carries parasites that can jump to local species that have no resistance to them. The African jewelfish occupies the same ecological niche as the endemic mojarra and gradually replaces it.

Mexico’s Comision Nacional de Áreas Naturales Protegidas (CONAMP), is now working with the Mexican Fund for Nature Conservation (FNCN) and the Canadian government agency Parks Canada to develop and implement a control and eradication program to tackle these five invasive species. The long-term survival of this highly unusual ecosystem may well depend on this program’s success.

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The Aqueduct of Padre Tembleque is Mexico’s 33rd UNESCO World Heritage Site

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Nov 102015
 

Earlier this year, UNESCO added a 16th century aqueduct in Mexico to its list of world heritage sites, bringing the total number of such sites in Mexico to 33.

The Aqueduct of Padre Tembleque was constructed between 1554 and 1571. It is named for the Franciscan friar, Francisco de Tembleque, who began the 48-kilometer-long aqueduct, which was built to transport water from what is now Zempoala, Hidalgo, to Otumba in the State of México. The aqueduct connects to an engineered water catchment area, springs, canals and distribution tanks.

Location of Aqueduct of Padre Tembleque

Location of Aqueduct of Padre Tembleque (Source: Google Maps)

The aqueduct was built with support from the local indigenous communities: “This hydraulic system is an example of the exchange of influences between the European tradition of Roman hydraulics and traditional Mesoamerican construction techniques, including the use of adobe.” (UNESCO)

Aqueduct of Padre Tembleque

Aqueduct of Padre Tembleque (Credit: Xinhua/INAH/NOTIMEX)

While much of the aqueduct is at ground level or underground, it crosses over the Papalote River near Santiago Tepeyahualco supported by a graceful series of high arches called the Main Arcade, 67 arches in total, and at one point 39 meters above the river (the highest single-level arcade ever built in an aqueduct “from Roman times until the middle of the 16th century.”)

The Aqueduct of Padre Tembleque is the largest single hydraulic engineering project completed in the Americas during Spanish colonial times and is a worthy addition to the World Heritage list.

For more information:

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More water meters for Mexico City

 Mexico's geography in the Press, Updates to Geo-Mexico  Comments Off on More water meters for Mexico City
Oct 122015
 

A recent OOSKAnews report says that Mexico City’s water authority (Sacmex) is seeking to purchase 27,835 more water meters that it plans to install in coming months. Sacmex supplies water to around 2 million separate addresses, of which 1.4 million are already metered. The latest purchase is part of Sacmex’s plan to ensure that 100% of connections to the water system are metered. Sacmex’s current budget includes $3.5 million for an additional 40,000 meters.

sacmex

At present, users without a meter pay a fixed bi-monthly tariff based on the building category, and intended type of water use (domestic/industrial/commercial).

Funding for the meters will be part of a $200 million World Bank-supported “Program to Improve the Efficiency of Operating Organizations” (PROME) which has already financed various projects across the country for urban areas with populations over 20,000. Projects already funded by the Progam include more efficient pumps, the updating of user databases with geo-referencing technology, and studies to gauge the robustness of indicators such as water pressure, water quality and leak detection.

Sacmex is also working on other distribution issues. Earlier this year – see Water in Mexico: a human right that is currently subsidized and wasted – Sacmex CEO Ramón Aguirre Diaz said that the agency required $430 million to combat leakages in the system (currently estimated at around 40% of supply), and claimed that a long-term program to fix the problem would be introduced next year.

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Water in Mexico: a human right that is currently subsidized and wasted

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Aug 172015
 

Two recent articles in OOSKAnews, a publication dedicated to news in the water industry, have profound implications for Mexico’s water supply situation. The first (10 July 2015) is a report of a meeting in Guanajuato of national water and water treatment specialists (Segundo Encuentro Nacional de Áreas Técnicas  de las Empresas de Agua y Saneamiento de México).

Selected quotes from the report include,

Mexico’s legal framework for water is out of date and does not reflect the country’s current reality…

Nationwide, water users only pay about 20% of the cost of production; 80% of water costs are subsidized, a situation that is not sustainable…

Legal reforms aimed at protecting human rights with regard to water had harmed service providers, who cannot cut off service to customers who fail to pay their bills.”

The report also comments on the on-going El Zapotillo dam project on the Rio Verde in Jalisco state, saying that it,

is a priority for President Enrique Pena Nieto’s administration, despite ongoing delays and legal conflicts. The $1.24 billion dollar project was approved in 2005 and is more than 80% complete. However, residents of Temacapulín, Acasico and Palmarejo have been fighting construction of the dam, which would flood their villages.”

sacmex

The second report focuses on Mexico City and the estimate by Ramón Aguirre Díaz, the head of Mexico City’s Water System (SACMEX), that fixing leaks in the city’s potable water distribution network would cost around US$430 million. This is a huge cost when compared to the system’s annual budget for maintenance and improvement of infrastructure of about US$135 million.

Aguirre claims that 40% of available water is lost because of leaks in the network. SACMEX is launching a program in 2016 to provide a long-term solution to the problem. In a press interview, the official said that, “A city like ours should be able to supply every citizen by producing 26 cubic meters/second, but currently our system requires 30.5 cubic meters/second”.

The sections of the city with the most severe losses are those like Coyoacán and Tlalpan built on the soft sediments of the former lake-bed, as well as those such as Miguel Hidalgo, Cuauhtémoc, and Benito Juárez, where the supply pipes are more than 70 years old. Combined, these areas house over 2.5 million people.

Aguirre also outlined the progress made in bringing reliable access to potable water to all 1.8 million inhabitants of Iztapalapa, one of the poorest and most densely populated sections of the city. Some 72,000 residents in Iztapalapa lack piped water supply to their homes, and therefore have to depend on provision from tanker trucks. Even those who do have access to piped water have to cope with inadequate pressure, poor water quality and frequent supply outages.

According to Aguirre, the city administration will meet its goal of reliable access to piped water for all of Iztapalapa by 2018. Reaching this point requires the construction of 22 water treatment plants and various other major infrastructure modernization projects.

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Mexico City’s Drinking Water Fountains

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Aug 102015
 

Earlier this summer, Mexico City’s Water System (SACMEX) inaugurated a network of 230 drinking fountains installed in public spaces across the city. The fountains are part of the city’s initiative to curb reliance on bottled water. (Mexicans consume more bottled water per person than any other country in the world).

water-fountains-mexico-city

Click for interactive map of Mexico City water fountains

The sites for the fountains were selected taking local water quality into account. An interactive website enables residents and visitors alike to find the locations of the fountains, and offers up-to-date information about the water quality parameters.

water-quality-xochimilco-july-2015.

Sample water quality report – Xochimilco, July 2015 [Click to enlarge]

Water from all the fountains is being tested on a regular basis to ensure that it complies fully with official water quality standards.

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Ground subsidence in Mexican cities

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May 112015
 

The sinking of parts of Mexico City into the former lake bed on which much of it is built is well documented, but to what extent does subsidence also affect other Mexican cities?

Estell Chaussard and her co-authors considered this question in their article entitled “Magnitude and extent of land subsidence in central Mexico revealed by regional InSAR ALOS time-series survey.” Subsidence, often resulting from over-depletion of ground water, has a range of human impacts, including decreased supply of safe water, an increase in flood risk, and a greater hazard threat from building or street failure.

In their time-series analysis of more than 600 Synthetic Aperture Radar (InSAR) images of central Mexico, the authors found evidence of significant subsidence in seventeen cities, including sixteen cities with a population of 100,000 inhabitants or more. The cities affected (with their population in parentheses) are listed here from east to west:

  • Puebla (2,500,000)
  • Mexico City (21,000,000)
  • Toluca (427,000)
  • Querétaro (825,000)
  • San Luis de la Paz (101,000)
  • Celaya (266,000)
  • San Luis Potosí (936,000)
  • Morelia (537,000)
  • Salamanca (144,000)
  • Irapuato (317,000)
  • Silao (147,000)
  • León (1,400,000)
  • Aguascalientes (735,000)
  • Zamora (186,000)
  • Guadalajara (3,800,000)
  • Ahuacatlán (6,500)
  • Tepic (261,000)

Their analysis suggested that the rates of subsidence over a two-year period were nearly constant at most locations, typically between 5 and 10 cm/yr. (In contrast, subsidence in Mexico City was around 30 cm/yr, in line with previous studies.)

ground-fissures

Ground failure by groundwater withdrawal subsidence. Credit: Natural Science, Vol. 6, No 3, 2014.

An earlier study – Subsidence risk due to groundwater extraction in urban areas using fractal analysis of satellite images – had found that the intense groundwater pumping regime in Irapuato for urban supply and agriculture (the area is one of Mexico’s main strawberry-growing centers) had resulted in 18 subsidence fault systems with a total length of 27 km, causing damages to more than 200 houses.

Meanwhile, previous work in nearby Celaya – Subsidence in Celaya, Guanajuato, Central Mexico: implications for groundwater extraction and the neotectonic regime – found that subsidence in that city was due to a complex combination of factors, and not entirely due to excessive groundwater extraction. Most earth fissures in the Celaya area were related to pre-existing structural features, and the authors suggested that thermal springs also appeared to play a role.

References:

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Ground subsidence in Mexico City threatens 10,000 homes

 Mexico's geography in the Press  Comments Off on Ground subsidence in Mexico City threatens 10,000 homes
Feb 052015
 

The local authorities in Iztapalapa, in the eastern section of the Mexico City Metropolitan Area, and one of the most interesting locations in Mexico in which to witness Easter celebrations, calculate that around 10,000 homes are in the area are at “high risk” of serious damage due to ground subsidence. Some parts of the city are falling in elevation as the ground contracts by up to 40 cm/yr.

Low-lying Iztapalapa is one of the most densely populated parts of the city, and is also prone to frequent flooding. Experts say that the severe damage evident in many buildings in the area has been occasioned by ground subsidence, due to the excessive volumes of water being pumped out of the subsoil to satisfy the insatiable demand of Mexico City.

In a short 3-minute news video in Spanish that is linked to in this recent article, Lourdes, a local resident offers us a tour of her home, showing us the damages caused by subsidence. She describes how “the crack that started from outside the house has widened every day and is now almost the width of a hand.” The video shows how the walls of her home are separating; the house is clearly in danger of collapse. Lourdes lives in this house with her four children; some rooms are already far too damaged to be safely used by the family.

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Access to safe water is a human right in Mexico

 Mexico's geography in the Press  Comments Off on Access to safe water is a human right in Mexico
Dec 132014
 

Earlier this year, David Korenfeld, the director of Mexico’s National Water Commission (Conagua), was chosen to head the inter-governmental council that oversees UNESCO’s International Hydrological Program (IHP). The IHP is the only inter-governmental program of the U.N. system devoted to water research, water-resources management, and education and capacity building.

In his acceptance speech, Korenfeld called for “greater synergy between decision makers and specialists to combine theory and practice” and stated that “significant challenges remain [in the water sector], including integral basin management, application of the human right to water and water security and sustainability in the context of climate change.

Recent events demonstrate that Mexican courts are happy to uphold the view that water is a basic human right. The 5 Dec 2014 issue of the OOSKAnews, a newsletter dedicated to water industry professionals, included the following short piece about a landmark recent decision by Mexico’s Supreme Court that represents the first ever Supreme Court decision in Mexico upholding the nation’s stance that “water is a basic human right.”

The Supreme Court has for the first time awarded an “amparo” (similar to an injunction, a remedy for the protection of constitutional rights), based on the human right to water.

In this case, members of the court unanimously sided with Lidia Velázquez Reynoso, a resident of the Ampliación Tres de Mayo area in the municipality of Xochitepec, in the state of Morelos.

In their ruling, the court said authorities must meet their obligation to provide Velázquez’s residence with “access, availability, and sanitation of water for personal and domestic consumption in a sufficient, safe, acceptable, and affordable form.” A lower court had already ruled in favor of Velázquez, but the case was appealed.

The Supreme Court said responsible authorities had failed to guaranteed regular delivery of water, since merely connecting Velázquez’s residence to the water system was not good enough. Water quality and volume must also be taken into account. The court said that the water must meet World Health Organization standards, and the volume provided must be at least 50 to 100 liters per person per day.

The court ordered authorities to not only deliver the water to Velázquez, but also to remit records showing that the water meets national and international standards.

(OOSKAnews, 5 December 2014)

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How does Mexico’s water footprint compare to that of other countries?

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Oct 292014
 

In a previous post, we saw how Mexico is a major net importer of “virtual” water. In this post we take a closer look at Mexico’s water footprint. The data throughout this post come from The Water footprint of Mexico in the context of North America (pdf file).

Individual products each have their own water footprint in terms of the total amount of water involved in their production, processing and marketing. For example a single cup of coffee represents (on average) a water footprint of 140 liters. Other water footprints include:

  • A single letter-sized sheet of paper – 10 liters
  • Microchip – 32 liters
  • Pair of leather shoes – 8000 liters
  • Glass of milk 200 liters
  • Glass of wine 120 liters
  • Tomato 13 liters
  • Hamburger (150 gram) 2400 liters

From numbers like these, it is possible to calculate the water footprint for an individual consumer in a particular country, and also for an average consumer in each country.

How does the water footprint in Mexico compare to other countries?

The water footprint of Mexico (WWF 2012)

The water footprint of Mexico (WWF 2012)

The graphic shows that Mexico’s total water footprint (all consumers) is 197,425 Hm³, of which 92% is agricultural, 3% industrial and 5% domestic. Only 57% of Mexico’s water footprint is internal, the remaining 43% is external (ie water used in other countries to make or produce items imported into Mexico). The average water footprint per person in Mexico comes to 5419 liters/day (or 1978 m³/year).

The global average water footprint (all countries, all consumers) in 2010 was 1,385 m³/y. However, some countries have much higher average water footprint/persons than others. For example, the average consumer in the USA has a water footprint of 2,842 m³/y, whereas in China and India the average water footprints are 1,071 and 1,089 m³/y respectively.

The water footprint of an average consumer worldwide  is primarily determined by their consumption of cereal products (contributes 27% to the average water footprint), followed by meat (22%) and milk products (7%).

It should be remembered that countries which heavily rely on foreign water resources may have significant impacts on water consumption and pollution elsewhere.

Full report:

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Mexico is a major net importer of “virtual” water

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Oct 132014
 

The concept of “virtual water” was developed by Professor J.A. Allan of King’s College (London University) and the School of Oriental and African Studies. Allan used it to support his argument that Middle Eastern countries could save their scarce water resources by relying more on food imports. The idea was sufficiently novel for Allan to be awarded the 2008 Stockholm Water Prize.

In Allan’s words, “The water is said to be virtual because once the wheat is grown, the real water used to grow it is no longer actually contained in the wheat. The concept of virtual water helps us realize how much water is needed to produce different goods and services. In semi-arid and arid areas, knowing the virtual water value of a good or service can be useful towards determining how best to use the scarce water available.”

As one example, producing a single kilogram of wheat requires (on average) around 1.5 cubic meters of water, with the precise volume depending on climatic conditions and farming techniques. The amount of water required to grow or make a product is known as the “water footprint” of the product.

Hoekstra and Chapagain have defined the virtual-water content of a product, commodity, good or service, as “the volume of freshwater used to produce the product, measured at the place where the product was actually produced”. The virtual water content is the sum of the water used in the various steps of the production chain.

Additional examples, showing the water footprint of producing one kilogram of:

  • biodiesel from soya –  11.4 cubic meters
  • beef –  15.4 cubic meters
  • butter –  5.5 cubic meters
  • chocolate – 17.0 cubic meters
  • pasta –  1.85 cubic meters
  • sugar (from cane) –  0.2 cubic meters

While the idea of virtual water has attracted some attention, its methodology is contested, and its quantification is not yet sufficiently precise to offer much potential for policy decisions.

Imports and exports of virtual water represent the “hidden” flows of water involved when food and other commodities are traded from one place to another. The map below (from Hoekstra and Mekonnen, 2012) shows the net imports (imports minus exports) of virtual water for different countries for the decade 1996-2005. Note that only the major flows are shown.

water-virtual-tradeIn North America, both the USA and Canada have a significant positive virtual water balance (i.e. they are major exporters of virtual water), whereas Mexico has a significant negative water balance, and is clearly one of the world’s largest importers of virtual water.

As Allan’s original work suggests, this is not necessarily bad news since it may imply that Mexico is currently using less of its own (limited) water resources than it might otherwise have to. In other words, Mexico’s virtual water imports may be delaying the inevitable crunch time when water usage becomes a critical limiting factor in the nation’s development.

Source of map

A.Y. Hoekstra and M.M. Mekonnen. 2012. The water footprint of humanity. Proc. Nat. Academy of Sciences, 109, 3232-7. Map was reproduced in “Spotlight on virtual water” by Stuart N. Lane in Geography, vol 99-1, Spring 2014, 51-3.

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Test wells being drilled to assess Mexico City’s deep water aquifer

 Mexico's geography in the Press, Updates to Geo-Mexico  Comments Off on Test wells being drilled to assess Mexico City’s deep water aquifer
Sep 132014
 

Pemex, Mexico’s state-owned oil giant, will start drilling the first of two deep exploratory wells in Mexico City later this month to investigate an aquifer deep below the city that is believed to hold vast quantities of potable quality water. For further background, please see our previous post on this topic:

The test wells are part of a $30 million multi-agency study now underway that incorporates experts from the Water System of Mexico City (SACM), the National Water Commission (CONAGUA), the engineering and geology departments of the National Autonomous University of Mexico (UNAM), and Pemex, which is providing the technology to drill the wells.

Later this month, Pemex will start drilling the first 2000-meter-deep test well in the Magdalena Mixhuca Sports City area, in the eastern part of Mexico City. Each well will cost an estimated $7.6 million to complete.

Schematic stratigraphy of the southern portion of the Basin of Mexico.

Schematic stratigraphy of the southern portion of the Basin of Mexico.
Source: Adapted from Mooser, 1990.

Ramón Aguirre, the CEO of SACM, says that the two test wells will target two different zones, increasing the chances of demonstrating the value of the aquifer as a viable source of water for Mexico City. In particular, Aguirre expects the wells to help confirm that there is an impermeable cap of clay separating the deep aquifer from the principal aquifer in the area (from which water is already extracted). An impermeable layer would mean that water could be safely removed from the deep aquifer without leading to downward drainage of water from the aquifer above. It is expected to take about two years for the initial studies to be completed.

In its National Water Plan, CONAGUA has warned that population growth in the Valley of Mexico could result in serious water shortages by 2030, reducing annual availability from about 4,230 cubic meters/person to less than 1,000 cubic meters/person.

The major aquifer currently used lies at a depth of between 60 and 400 meters and is heavily over-utilized. There are about 630 wells in the Federal District alone; all are overexploited and have an average life expectancy of 30 years. Current extraction from the aquifer is around 17,000 liters/second, while its natural recharge capacity is only 8000-9000 liters/second. It is believed that the deep aquifer could be capable of supplying approximately 5000 liters/second.

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Sep 082014
 

In mid-August 2014, this significant fissure (see image) appeared near the city of Hermosillo in northern Mexico, with some press reports opting for headlines such as “The Earth Splits Open”:

fissure-hermosillo-eyewitness-news

While many press reports, especially those in English, tried to link this fissure to faulting and earthquake movements, others were more cautious, saying it was caused by movement of water underground followed by subsidence. Which version is correct? Probably neither is completely correct, since geography often fails to provide a single, definitive reason for things!

The crack is about 1000 meters (two thirds of a mile) long and up to 7 or 8 meters wide and 10 meters deep. While some press reports erroneously claimed that the crack extended across the main, paved, highway #26 between Hermosillo and the coast, its location was actually some distance away from the main highway. The road shown in the image above is a rural, unpaved road about 80 kilometers (50 miles) west of Hermosillo, in an area of farmland, some of which is irrigated.

Could the fissure have been formed by faulting associated with earth tremors or an earthquake? If this was the cause, the fence line, and the line taken by the road would have shifted position and no longer be straight. The image clearly shows that the road has been severed, but provides no evidence that the two sides have shifted position. Indeed, a close-up view confirms that even the existing fence remains in place:

fissure-hermosillo-fence-line

The available evidence therefore rules out faulting (or earth tremors or earthquakes) as the cause of the crack.

Could the fissure have been caused by an underground flow of water followed by subsidence (the collapse of overlying rocks)? This certainly looks more likely though it is hard to imagine significant underground flows of water in an area that is as flat as this. On the other hand, this is (a) an area of newly constructed irrigation ditches and ponds, and (b) it received heavy rainfall a few days before the crack was reported.

In all probability, the fissure began as a deep but very narrow “subsidence fissure” where differences in irrigation (or in water extraction) caused some parts to be much wetter than others. The soil and rock particles in wetter areas would tend to expand, while those in drier areas would tend to contract. Such differences could lead to the formation of small initial fissures.

Once the fissure had been started, localized heavy rains and the resulting overland flow could then result in streams flowing (temporarily) in these initial fissures. The moving stream water would rapidly widen and deepen the fissures into the scale of crack shown in the photos. The initial fissure may have been formed several years before this widening process occurred.

For a more detailed look at the evidence for this fissure’s formation (and its true location), see Debunked: The Earth Splitting Open – Giant Crack in Mexico.

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Recent progress in waste water treatment in Mexico

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Aug 252014
 

Two wastewater treatment plants have been in the news recently. The first is the $230 million Agua Prieta wastewater treatment plant, located north of Guadalajara in Jalisco, which was formally inaugurated last month. It is the first stage in a plan to restore the heavily polluted Santiago River back to health. The Santiago is the outflow from Lake Chapala and receives pollutants from the industrial zone of El Salto outside Guadalajara. The initial capacity of the Agua Prieta plant is 6,500 liters/second, almost all of which is returned to the river after treatment.

The plant was built by a consortium led by ICA subsidiary Conoisa, Atlatec, and Servicios de Agua Trident under a 20-year concession. President Enrique Peña Nieto claims on his government webpage that, “Integrated, sustainable water management is a government priority. The challenge is even greater because almost 50% of the wastewater returned to the environment does not undergo any form of treatment… The Agua Prieta Wastewater Treatment Plant in Zapopan… [will] improve the quality of life of 3.3 million inhabitants in the metropolitan area of Guadalajara… It will treat 82% of the wastewater in the area, and 100% when the complementary sewage works are completed.”

agua-prieta-wastewater-According to government figures, waste water treatment coverage at the national level is currently 50.3%, with a 2018 target of 63%. Agua Prieta has raised national coverage to 53.3%, and will boost it to 54.3% once the plant is operating at full capacity and treating 8,500 liters/second of wastewater. At the state level, Jalisco is now treating 32% of its wastewater.

The Agua Prieta plant is currently the largest of its kind in Mexico and is powered by biogas derived from the wastewater sludge. However, an even larger plant is under construction, in the state of Hidalgo in central Mexico. The Atotonilco Wastewater Treatment Plant is being built by a consortium, including Mexican construction companies ICA and IDEAL, Mitsui subsidiary Atlatec and Spanish firm Acciona Agua, that won the concession to design, build, and operate this plant for 22 years, at which point the plant will be transferred to federal ownership. Work began in 2010 and is due to be completed by 2015.

The Atotonilco Wastewater Treatment Plant will be the largest wastewater plant in Latin America and one of the largest in the world, with a biological treatment capacity of 23,000 liters/second (1.99 million m3/day). The wastewater treatment is performed by a series of conventional processes, with an additional chemical process during the rainy season. Treated waters from this plant are already being used in agriculture without any additional cleaning steps. The plant is self-sufficient in terms of energy usage, since it converts the methane offgas from the wastewater sludge into electrical energy.

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UNESCO appoints Mexico to oversee its International Hydrological Program

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Jul 102014
 

Mexico has been chosen to head the inter-governmental council that oversees UNESCO’s International Hydrological Program (IHP). The IHP is the only inter-governmental program of the U.N. system devoted to water research, water-resources management, and education and capacity building.

A joint statement issued by Mexico’s Environment Secretariat and Foreign Relations Secretariat says that David Korenfeld, the director of Mexico’s National Water Commission (Conagua) has been named the council’s president for the next two years. In his acceptance speech, Korenfeld called for “greater synergy between decision makers and specialists to combine theory and practice” and stated that “significant challenges remain [in the water sector], including integral basin management, application of the human right to water and water security and sustainability in the context of climate change.

Korenfeld said that one of the IHP’s main objectives must by to strengthen “a confluence of science, technology and public policy aimed at reducing the social and environmental vulnerability of emerging and developing countries amid the challenges of climate change.”

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Mexicans drink more bottled water per person than anywhere else in the world

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May 032014
 

Mexicans are the world’s largest consumers of bottled water, both in individual small bottles (1.5 liters or less) and in garrafones (large, 20-liter bottles).

The main reason is a lack of confidence in the purity of public water supplies, resulting in part from perceived inefficiencies in how city water systems are managed and maintained. These concerns may be valid in some parts of Mexico, but are certainly not the case in all areas. Other factors resulting in a high acceptance of bottled water are the convenience, Mexico’s warm climate, and the vigorous publicity and advertising campaigns carried out by bottled water companies. It does not help that consumer groups repeatedly express concerns even about the quality of water in garrafones, claiming that some companies apparently take insufficient precautions to prevent its contamination.

For its part, the National Water Commission repeatedly claims that the problem of water quality is not due to the main distribution lines in Mexico, but to problems at a local level, in the final stages of the network between supply and consumers.

garrafon

Typical 20-liter garrafon

According to Euromonitor International, bottled water consumption in Mexico in 2013 averaged 186.7 liters/person, well ahead of Italy (175.1 liters/person), Nigeria (163.1), Turkey (147.7) and Spain (143.2). [Note that an earlier estimate in 2010 by Beverage Marketing Corporation put per person consumption of bottled water in Mexico at 234 liters a year, with equivalent figures for Italy, Spain and the USA of 191 liters, 119 liters and 110 liters respectively; the difference from 2010 to 2013 is almost certainly due to methodological differences].

Mexico consumes about 13% of all bottled water sold in the world! The only countries consuming more bottled water (in total volume) than Mexico were the much more populous countries of the USA, China and Nigeria.

Bottling water is a highly profitable business. The cost of 1,000 liters from the tap is 25 pesos (about 2 dollars); the same water, sold in bottles, is worth between 6000 and 8500 pesos (450 to 650 dollars).

The bottled water market in Mexico has grown from 6.5 billion dollars in 2009 to 10.4 billion in 2013, according to Euromonitor.  It is dominated by three foreign firms: Danone (France), Coca-Cola (USA) and PepsiCo (USA). Between them, they supply 82% of the market, according to a Euromonitor report, with the three leading brands being Bonafont (Danone) which accounts for 38% of the market, followed by Ciel (Coca-Cola) which has a 25% share and Epura (PepsiCo) 19%.

The cost of bottled water in an average Mexican household is considerable. For instance, assuming an average consumption of 15.55 liters/month/person, and that all water is bought in 1-liter bottles (which cost about 8 pesos each), then the monthly cost per household would be close to 500 pesos (38 dollars).

An industry dominated by four multinationals

Inside the Bottle: An Exposé of the Bottled Water Industry, a book by Canadian activist Tony Clark, provides a vivid and disturbing portrayal of how, worldwide, four big companies – Nestlé, PepsiCo, Coca-Cola and Danone – dominate the bottled water industry. As summarized by infinitewaterinc.com, the book examines several key issues of public concern about the operations of these companies, including how they:

  • pay little or nothing for the water they take from rural springs or public systems;
  • turn ‘water’ into ‘water’ through elaborate treatment processes;
  • produce a product that is not necessarily safer then, nor as regulated as, tap water;
  • package it in plastic bottles made of environmentally destructive toxic chemicals;
  • market it to an unsuspecting public as ‘pure, healthy, safe drinking water’; and
  • sell it at prices hundreds, even thousands of times more costly than ordinary tap water.

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World’s longest underground river flows deep beneath the Yucatán Peninsula

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Feb 102014
 

In January 2007, the world’s longest underground river was reported from Mexico’s Yucatán Peninsula. [Prior to that date, the honor was held by the Puerto Princesa Subterranean River in the Philippines]

The Sac Actun (“White Cave”) river system in the Yucatán Peninsula wanders for 153 km (95 miles) through a maze of underground limestone caves. It took British diver Stephen Bogaerts and his German colleague Robbie Schmittner four years to explore the caverns using underwater scooters and specially rigged gas cylinders, before they finally discovered a connection between the Yucatán region’s then second- and third-longest cave systems, known respectively as Sac Actun and Nohoch Nah Chich (“Giant Birdcage”). Following the discovery of a link, the entire system is now known as Sac Actun. The system has a total surveyed length (including dry caves) of 319 kilometers (198 mi), making it the longest cave system in Mexico, and the second longest worldwide. [The longest is the dry Mammoth Cave System, Kentucky, USA, which measures 643.7 km (400 mi) in length].

Sac-Actun cave system

Sac-Actun cave system

Vying with Sac Actun for the title of longest surveyed underwater cave system is the nearby Sistema Ox Bel Ha (“Three Paths of Water”), also in the Tulum municipality of Quintana Roo. As of August 2013, surveys had measured 256.7 kilometers (159.5 mi) of underwater passages.

The underground passages and caverns of the Yucatán Peninsula have been a favored site for cave explorers for decades. Formal mapping of the systems has taken more than 20 years of painstaking work. Access to the systems is via the hundreds of sinkholes (cenotes) that litter the surface of the Peninsula. The Sac Actun system alone includes more than 150 cenotes.

Water management was critical to the Maya as they developed their advanced civilization in this area, a region with very limited surface freshwater. Many of the cenotes in the Yucatán Peninsula have archaeological importance and were utilized by the Maya for ceremonies. Perhaps the best-known (and most visited) cenote is the Sacred Cenote (cenote sagrado) at the archaeological site of Chichen Itza.

The caverns of the Yucatán Peninsula were formed as a result of the slow solution of limestone over thousands of years by percolating, slightly acidic, rainwater. In some cases, cave formations, such as stalactites and stalagmites, have later grown in the caves, formed drip-by-drip from the slow deposition of calcium carbonate from calcium-saturated ground water.

Because the average elevation of the Yucatán Peninsula is only a few meters above sea level, the water in many of the caves is “layered”, with a lens of freshwater overlying a layer of salt water. Rainwater that soaks into the ground becomes ground water, which then moves slowly along the watertable to eventually reach the ocean.

Cave researchers are worried that tourist developments in the Yucatán Peninsula will have adverse impacts on underground water systems, both in terms of water quantity (because of the amounts of fresh water extracted for domestic and tourist use) and in terms of water quality, because even point sources of water pollution (such as excess fertilizers from a golf course) could contaminate underground water supplies over a wide area.

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Water management progress in the Lerma-Chapala basin

 Books and resources  Comments Off on Water management progress in the Lerma-Chapala basin
Jan 112014
 

The Lerma-Chapala Basin (see map) is one of Mexico’s major river systems, comprising portions of 127 municipalities in five states: México, Querétaro, Michoacán, Guanajuato and Jalisco.

The basin has considerable economic importance. It occupies only 2.9% of Mexico’s total landmass, but is home to 9.3% of Mexico’s total population, and its economic activities account for 11.5% of national GDP. The basin’s GDP (about 80 billion dollars/year) is higher than the GDP of many countries, including Guatemala, Costa Rica, Honduras, Paraguay, Bolivia, Uruguay, Croatia, Jordan, North Korea and Slovenia.

Lerma-Chapala Basin

The Lerma-Chapala Basin. Click map to enlarge. Credit: Tony Burton / Geo-Mexico

Given this level of economic activity, it is probably not surprising that the pressures on natural resources in the basin, especially water, are enormous. Historically, the downstream consequence of the Lerma Basin’s agricultural and industrial success has been an inadequate supply of (heavily polluted) water to Lake Chapala.

Following decades of political inactivity or ineffectiveness in managing the basin’s water resources, solid progress finally appears to have been made. Part of the problem previously was a distinct lack of hard information about this region at the river basin scale. The statistics for such key elements as water usage, number of wells, replenishment rates, etc. were all (to put it politely) contested.

Fortunately, several scientific publications in recent years have redressed the balance, and the Lerma-Chapala Basin is now probably the best documented river basin in Mexico. This has allowed state and federal governments to negotiate a series of management agreements that are showing some positive signs of success.

The first of these key publications was “The Lerma-Chapala Watershed: Evaluation and Management“, edited by Anne M. Hansen and Manfred van Afferden (Klewer Academic/Plenum Publishers, 2001). This collection of articles featured contributions from researchers in several universities and research centers, including the University of Guadalajara, Mexican Institute of Water Technology, Autonomous University of Guadalajara, Baylor University, the Harvard School of Public Health and Environment Canada. Click here for my comprehensive description and review of this volume on MexConnect.com.

Perhaps the single most important publication was the Atlas de la cuenca Lerma-Chapala, construyendo una visión conjunta in 2006. Cotler Ávalos, Helena; Marisa Mazari Hiriart y José de Anda Sánchez (eds.), SEMARNATINE-UNAM-IE, México, 2006, 196 pages. (The link is to a low-resolution pdf of the entire atlas). The atlas’s 196 pages showcase specially-commissioned maps of climate, soils, vegetation, land use, urban growth, water quality,  and a myriad of other topics.

More recently, a Case Study of the Lerma-Chapala river basin: : A fruitful sustainable water management experience was prepared in 2012 for the 4th UN World Water Development Report “Managing water under uncertainty and risk”. This detailed case study should prove to be especially useful in high school and university classes.

The Case Study provides a solid background to the Lerma-Chapala basin, including development indicators, followed by a history of attempts to provide a structural framework for its management.

In the words of its authors, “The Lerma Chapala Case Study is a story of how the rapid economic and demographic growth of post-Second World War Mexico, a period known as the “Mexican Miracle”, turned into a shambles when water resources and sustainable balances were lost, leading to pressure on water resources and their management, including water allocation conflicts and social turbulence.”

On a positive note, the study describes how meticulous study of the main interactions between water and other key development elements such as economic activity and social structures, enabled a thorough assessment on how to drive change in a manner largely accepted by the key stakeholders.

The early results are “stimulating”. “Drawbacks and obstacles are formidable. The main yields are water treatment and allocation, finances, public awareness, participation and involvement. The main obstacles are centralization, turbid interests, weak capacity building, fragile water knowledge; continuity; financial constraints; and weak planning.”

Sustainable water usage is still a long way off. As the Case Study cautions, “There is still much to do, considering the system Lerma-Chapala responds directly to a hydrologic system where joint action and especially abundant involvement of informed users is required, to achieve sustainable use of water resource.”

One minor caveat is that the Case Study does not offer full bibliographic reference for all of the maps it uses, which include several from the previously-described Atlas de la cuenca Lerma-Chapala, construyendo una visión conjunta.

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The city of León in Guanajuato uses Google Earth to monitor its water usage

 Mexico's geography in the Press  Comments Off on The city of León in Guanajuato uses Google Earth to monitor its water usage
Dec 212013
 

León, in the state of Guanajuato, is a prosperous industrial city (population 1.6 million), which built its wealth by processing animal hides obtained from the surrounding ranching areas into all manner of leather goods, especially clothing, accessories and shoes, the range of which goes from casual to ultra-fashionable. León does not just have shoe stores, it has shoe shopping centers!

Founded in 1576 and named for a province in Spain, the city became an important colonial center, well positioned on the main trading routes. It later became important for anti-colonial sentiment. Brothers Juan and Ignacio Aldama, born here in the eighteenth century, became key figures in the Independence movement led by Father Miguel Hidalgo. Shortly after Independence, the city’s shoe industry started, introduced by skilled craftsmen from Puebla.

Like any wealthy Mexican city, León has lots of old buildings, including the eighteenth century Cathedral with its fine choir stalls and the Nuestra Señora de los Angeles church, embellished by the interesting carvings of a native craftsman. The impressive Town Hall, with its elaborate façade, is a nineteenth century addition, as is the Manuel Doblado Theatre, designed by José Noriega who also had a hand in building theatres in several other cities in the region, including Guanajuato, Aguascalientes and San Luis Potosí.

leon-agua-monitoreoThe city would have even more old buildings today were it not for the disastrous flood of June 1888 when torrential downpours caused the Río Gómez to burst its banks. A wall of water and debris swept away more than 2000 homes, causing 200 fatalities and making 20,000 homeless. Major engineering works shortly afterwards have ensured that the city is now safe from future events of this kind.

The city has grown into one of Mexico’s most important industrial centers. The position of León has been key to its success. The city is located in central Mexico, close to the major urban areas of Mexico City, Querétaro and Guadalajara. On a broader scale, it is close to the major export markets of the USA, Canada and Central America. Market proximity is enhanced by an excellent communications network, including good road and rail links, easy access to several major airports, and to seaports such as Manzanillo.

Like most cities in central Mexico, one of León’s most pressing problems is how to ensure that its residents and industries have an adequate supply of potable water, even though the city was rated #1 in the country in terms of overall performance in this regard in the 2011 report “Water Management in Mexican Cities”.

In order to monitor the city’s water usage more effectively, engineers from the León Potable Water and Sewerage System (SAPAL) have introduced a sophisticated software system that provides real time data about the city’s water network and wells. It enables the engineers to overlay data like address, owner, account status, and water consumption onto a series of screen connected to Google Earth.

The system was developed in-house by local engineers, starting more than a decade ago, at a fraction of the cost of purchasing a similar system from an external provider. The León system is already being closely studied by water experts from other cities and countries.

SAPAL’s Control and Monitoring Center has a video wall, measuring 7.5 by 2 meters, with 24 LED screens. The center functions 24 hours a day, monitoring details of water distribution for more than 9000 data points, including wells, pipelines and holding tanks.

According to Agustín Báez, the city official responsible for SAPAL operations, the objective is “to have measurement from point of extraction to final use” since “what is not measured is not controlled.”

Sources:

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Mexico City explores deep water aquifer

 Mexico's geography in the Press, Updates to Geo-Mexico  Comments Off on Mexico City explores deep water aquifer
Dec 092013
 

Background: The Valley of Mexico is an interior basin about 9000 square km in area. The basin floor sits at an elevation of 2200 meters above sea level and is surrounded by mountains that rise up to more than 5000 meters above sea level. It receives around 700 mm of rainfall a year, with a rainy season from late May to September.

The basin was originally the site of several lakes and marshes, and much of it is underlain by lacustrine sediments up to 100 m thick, beneath which are alluvial sediments up to 500 m thick (see geological cross-section below). These sediments are interstratified with layers of volcanic basalt. Beneath the alluvial sediments are 100 m to 600 m of volcanic deposits, which form the principal Mexico City aquifer (found about 500 m to 1000 m below Mexico City).

As Mexico City has grown, and water demands have increased, this main aquifer has been greatly overexploited, leading to a drop in the level of the water table underground, accompanied by ground subsidence that has had serious consequences for Mexico City:

Feasibility study of a deep aquifer

The National Water Commission (CNA) and Mexico City Water System (SACM) are undertaking a 3-year, 23-million-dollar feasibility study to assess the potential of an aquifer that lies more than 2000 meters below Mexico City. (Our earlier, initial report about this aquifer is here).  The project includes experts from Pemex, CFE and UNAM’s Institute of Geophysics.

Schematic stratigraphy of the southern portion of the Basin of Mexico.

Schematic stratigraphy of the southern portion of the Basin of Mexico.
Source: Adapted from Mooser, 1990.

Initial exploratory wells have shown that the deep aquifer’s water quality is superior to that currently derived from the overexploited shallower wells that extend to depths of around 800m.

It is hoped that the feasibility study will confirm that water from the deep aquifer could be an additional viable source of freshwater for the city. Assuming the deep aquifer is hydrologically independent of the shallower aquifers, this  would not only reduce the need to pump water from the shallower aquifers, but would also avoid the ground subsidence resulting from continued shallow-water extraction. The feasibility study will assess whether or not the deep water aquifer is “fossil” water or is still being recharged from precipitation and underground throughflow. If it is being recharged, the experts will calculate its recharge rate to determine the aquifer’s maximum sustainable yield. (The maximum sustainable yield is the “additional groundwater output from the system which will cause minimal and acceptable levels of stress to the ecosystem with maximum benefits to the society and to the economy”).

The first test well is likely to be sunk in the Magdalena Mixhuca Sports City area, in the eastern part of Mexico City.

This potential deep aquifer source of freshwater could play a vital part in ensuring that future generations of Mexico City residents have a dependable and sustainable water supply.

Mexico’s consideration of utilizing deep water aquifers runs counter to the prevailing wisdom in the US where it has long been argued that deep water aquifers will be too costly to utilize for fresh water, will never be used, and are therefore more useful as a repository for waste and can be intentionally polluted.

As a result, as this Huffington Post article explains, “policy-makers often exempt these deep aquifers from clean water protections and allow energy and mining companies to inject pollutants directly into them.”  The article adds that, “the U.S. Environmental Protection Agency has issued more than 1,500 permits for companies to pollute such aquifers in some of the driest regions. Frequently, the reason was that the water lies too deep to be worth protecting.”

References:

Mooser, F. 1990. “Estratigrafía y estructura del Valle de México en el subseulo de la cuenca del Valle de México y su relacíon con la Ingeniería de cimentaciones, a cinco anos del sismo”, in Revista de la Sociedad Mexicana de Mecánica de Suelos. Mexico, D.F.

For a detailed description of Mexico City’s shallower aquifer and its exploitation, see Mexico City’s Water Supply: Improving the Outlook for Sustainability (1995) (viewable online or register for a free download)

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Resources about the geography of chinampas, an ancient form of sustainable agriculture

 Books and resources  Comments Off on Resources about the geography of chinampas, an ancient form of sustainable agriculture
Sep 302013
 

This post describes some of the many online resources about chinampas, one of Mexico’s ancient and most important indigenous forms of sustainable agriculture.

For photos, the best starting point is Dr. Jason Turner’s site about chinampas which includes an extensive bibliography about chinampas as well as several “Virtual Field Trips” (photo sequences). Even though these photo sequences often lack any accompanying descriptions or captions, they cover a wide range of ideas, and are organized in self-explanatory groups such as:

For an article describing a recent tour of a working chinampa in Xochimilco’s Ecological Reserve. illustrated with great photos, try Touring Xochimilco’s farms with De la Chinampa written by Lesley Téllez (self-described food writer with a “deep love for Mexican food and culture”) on her blog “The  Mija Chronicles”.

Youtube also has a variety of chinampa-related resources. In English, the best introduction is Discovery Atlas – Mexico: Xochimilco which provides a good background to the history and covers the basics.

Two Spanish-language Youtube resources provide valuable additional information. Each video lasts about 5 minutes, but neither video has English language subtitles.

The first is Divina Ciudad: De la chinampa a la mesa which looks at one specific project designed to help raise public awareness and aid the conservation of the remaining chinampas in Xochimilco, on the south-eastern outskirts of Mexico City. This project supplies consumers with fresh produce grown on the chinampas in Xochimilco or sourced from within 150 km. See the project’s website – De La Chinampa – for more information.

The second Spanish language video is Profeco TV Reporte Especial: Productos de la Chinampa, un ejemplo de consumo sustentable, This video, made by the federal consumer protection agency Profeco, explains how the produce grown on the chinampas is pesticide-free and relies on sustainable production methods. It calls on viewers to “learn more about the method and help ensure that chinampas do not disappear.”

Book (Spanish)

  • Rojas R., Teresa (Coord) 1995. Presente, pasado y futuro de las chinampas. Mexico DF: Ciesas/Patronato del Parque Ecológico de Xochimilco A.C. This is a collection of 25 papers presented at a 1990 international conference in Mexico City.

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Sep 092013
 

Prior to European contact in 1519, what did the Aztec people eat?

The basis of Aztec diet was corn (maize). They cultivated numerous varieties of corn, as well as many other crops including beans, amaranth and squash. Some dishes were seasoned with salt and chili peppers. This mix of items provided a balanced diet that had no significant vitamin or mineral deficiency.

In addition, the Aztec diet included tomatoes, limes, cashews, potatoes, sweet potatoes, peanuts, cacao (chocolate), wild fruits, cactus, mushrooms, fungi, honey, turkey, eggs, dog, duck, fish, the occasional deer, iguana, alongside insects such as grasshoppers. From the lake water, they scooped high protein algae (tecuitlatl), which was also used as a fertilizer.

How did they obtain their food?

The Mexica (who later became the Aztecs) faced a particular dilemma, largely of their own making. Mexica (Aztec) legend tells that they left their home Aztlán (location unproven) on a lengthy pilgrimage lasting hundreds of years. They were seeking a specific sign telling them where to found their new capital and ceremonial center. The sign was an eagle, perched on a cactus. Today, this unlikely combination, with the eagle now devouring a serpent, is a national symbol and appears on the national flag.

Artist's view of the Aztec capital Tenochititlan in the Valley of Mexico

Artist’s view of the Aztec capital Tenochititlan in the Valley of Mexico

The dilemma arose because they first saw this sign, and founded their new capital Tenochtitlan, on an island in the middle of a lake in central Mexico. An island linked by causeways to several places on the “mainland” might have had some advantages in terms of defense, but supplying the growing settlement with food and fresh water was more of a challenge.

Much of their food came from hunting and gathering, and some food was brought by long-distance trade, but space for farming, especially on the island, was at a premium.

The Aztecs solved their dilemma of how to supply food to their island capital by developing a sophisticated wetland farming system involving raised beds (chinampas) built in the lake (see image below). Originally these chinampas were free-floating but over time they became rooted to the lake floor. The chinampas were separated by narrow canals, barely wide enough for small boats or canoes.

Artist's representation of chinampa farming

Artist’s representation of chinampa farming

From an ecological perspective, these chinampas represented an extraordinary achievement, a food production system which proved to be one of the most environmentally sustainable and high-yielding farming systems anywhere on the planet!

Constructing and maintaining chinampas required a significant input of labor, but the yields per unit area could be very high indeed, especially since four harvests a year were possible for some crops. The system enabled fresh produce to be supplied to the city even during the region’s long dry season, whereas food availability from rain-fed agriculture was highly seasonal.

Artist's interpretation of chinampa construction (from Rojas 1995)

Artist’s interpretation of chinampa construction (from Rojas 1995)

The planting platforms or chinampas were built by hand, with alternate layers of mud, silt and vegetation piled onto a mesh of reeds or branches. Platforms, often but not necessarily rectangular, were about 10 meters wide and could be 100 meters or more in length. Willow trees were often planted on the edges of platforms to help stabilize them and provide shade for other plants and for the canals that separated the platforms. Interplanting crops was common, and polyculture was the norm. For many crops, multicropping (several crops in a single year) was possible.

Because the planting platforms were close to water, extremes of temperature were dampened, and the likelihood of frost damage to crops reduced. The root systems of crops had reliable access to fresh water (sub-irrigation). The canals provided a variety of habitats for fish. The mud from the bottom of canals was periodically dredged by hand and added to the platforms, supplying nutrients and preserving canal depth. Together with the regular addition of waste organic material (compost), this replenished the platforms and meant that their fertility was maintained over very long periods of time.

The system could even cope with polluted water, since the combination of constant filtration on the platforms, and aquatic weeds in the canals, partially removed most impurities from the water.

Where can chinampas be seen today?

Archaeologists have found vestiges of chinampas in several regions of Mexico, some dating back almost 3000 years.

Mexico’s best known chinampas today are those in Xochimilco on the south-eastern outskirts of Mexico City. Xochimilco is a Unesco World Heritage site, but faces heavy pressure from urban encroachment and highway construction. Xochimilco’s canals (with chinampas separating them) are some of the last surviving remnants of the large lake that occupied this valley when the Mexica founded Tenochititlan.

Xochimilco (Wikipedia; creative commons)

Xochimilco (Wikipedia; creative commons)

Visiting Xochimilco’s canals and market is a popular weekend excursion for Mexico City residents and tourists alike. However, the modern-day chinampas of Xochimilco are not the same as they would have been centuries ago. First, the total area of chinampas in Xochimilco is only a fraction of what once existed. Secondly, some of the chinampas have been abandoned, while on others chemical fertilizers and pesticides are often used. Thirdly, the area now has many exotic species, including introduced species of fish (such as African tilapia and Asian carp) that threaten native species. Numbers of the axolotl (a local salamander), a prized delicacy on Aztec dinner tables, are in sharp decline. Fourthly, the water table in this area fell dramatically during the last century as Mexico City sucked water from the underground aquifers causing local springs that helped supply Xochimilco to dry up completely. Rubble from the 1985 Mexico City earthquake was also dumped in Xochimilco’s canals.

Lakes in some other parts of Mexico were also used for chinampa farming. For example, in Jalisco, just west of Guadalajara, Magdalena Lake “was a prime source of food for the 60,000 or so people living close to the Guachimontones ceremonial site (settled before 350 BC) in Teuchitlán. They learned to construct chinampas, fixed mud beds in the lake, each measuring about 20 meters by 15 meters, which they planted with a variety of crops… The remains of hundreds of these highly productive islets are still visible today.” (Western Mexico: A Traveler’s Treasury, p 69)

Chinampa farming was one of the great agricultural developments in the Americas. It was, and still can be, an environmentally-sensitive and sustainable method of intensive wetland agriculture.

If you enjoyed this…

You might well enjoy my latest book: Mexican Kaleidoscope: myths, mysteries and mystique

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Case study of the June 2013 ecocide in Hurtado Reservoir, Jalisco

 Mexico's geography in the Press  Comments Off on Case study of the June 2013 ecocide in Hurtado Reservoir, Jalisco
Jul 042013
 

This post presents a short case study of the dramatic ecocide in the Hurtado Reservoir in Jalisco a week ago that resulted in the sudden death of between 200 and 500 tons of fish.

What?

  • The ecocide killed between 200 and 500 tons of fish
  • 30 local residents were affected by gastrointestinal problems
  • 15 of them required treatment in local health centers

Where?

The ecocide occurred in the Hurtado Reservoir (Presa del Hurtado, aka the Valencia Dam) in Jalisco, mid-way between the villages of San Isidro Mazatepec and Bellavista, the location of a sugarcane mill (see map). The reservoir can hold up to 8,000,000 cubic meters of water. The two municipalities involved are Acatlán de Juárez and Tlajomulco de Zúñiga. The most affected community is the small village of San Pedro Valencia (about 300 inhabitants),

Location of Hurtado Reservoir (extract from INEGI 1:250,000 map)

Location of Hurtado Reservoir (extract from INEGI 1:250,000 map)

When?

The first reports were made on 25 June when a local government official in San Pedro de Valencia, in the municipality of Acatlán de Juárez, reported to state environmental protection officials that the water in the Hurtado Reservoir was contaminated with something smelling like molasses. Within 48 hours, officials had identified the source, and had conducted a formal inspection, reporting that the water was dark brown in color and contaminated with molasses.

Why?

According to press reports, an unlicensed firm in nearby Potrero los Charros was using molasses (a by-product of sugarcane mills) as an ingredient to make cattle food. Some of the molasses (melaza) was dumped into the San Antonio stream which carried them into the reservoir.

The problem arose because molasses have a very high biochemical oxygen demand (BOD). This means that they require large amounts of oxygen as they decompose. In this case, they required more oxygen than was available in the water in the reservoir, reducing the water’s dissolved oxygen content, effectively depriving all aquatic life of oxygen. While final results are pending, the fish are believed to have died of oxygen starvation.

Effects

  1. The local fishing cooperative of the Hurtado Reservoir has agreed to accept a moratorium on catching, selling or consuming local fish. The fishermen normally catch and market about 100 kg of fish a day.
  2. Health services are offering vaccinations to local residents and all those involved in the environmental clean-up.
  3. 18 local restaurants are closed until further notice. When they reopen, they will likely have to purchase fish from further away (eg the fish market in Guadalajara) at a higher price than they previously paid for local fish
  4. About 100 fish traders in nearby towns (including Tala, Acatlán de Juárez and Villa Corona) have lost a source of income.

Responses

  1. Within 48 hours of the first report, authorities had ordered the business responsible for the pollution to take immediate remedial action. Meanwhile, authorities began to clean up the dead fish. The fish are being buried in a 30 meter by 2 meter trench about one km away from the lake.
  2. Federal officials from the National Water Commission and the Environmental Secretariat were quickly on the scene; they promised access to federal financial assistance.
  3. Most of the clean up was carried out by about 100 local fishermen and volunteers, including firefighters.
  4. State health officials have closed the 18 small fish restaurants near the lake until further notice
  5. Local officials are also cleaning up the storage area, using tanker trucks to remove an additional 8,000 tons of molasses for appropriate disposal elsewhere.
  6. The municipality of Tlajomulco has issued the owner of the company with a fine of about 1.5 million pesos ($120,000) and further legal action is underway.

Remediation

  • Environmental expert Gualberto Limón Macías estimates it will take between two and four years to rehabilitate the reservoir. The priority is to re-oxygenate the water, possibly using solar-powered pumps, and seed the reservoir with young fish.
  • The University of Guadalajara has promised to arrange for a team of experts to provide specialist advice about how best to rehabilitate the lake.

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Five Mexican beaches gain international Blue Flag certification

 Mexico's geography in the Press  Comments Off on Five Mexican beaches gain international Blue Flag certification
Jun 032013
 

For the first time ever, five Mexican beaches have been awarded Blue Flag certification. The Blue Flag system is a voluntary, international eco-label program run by the non-government, non-profit organization the Foundation for Environmental Education that recognizes beaches where water quality is excellent, where information and environmental education is readily available, and which are well managed, with high standards of safety and services. The announcement was made in Copenhagen, Denmark, where Blue Flag certification was given to 3100 beaches and 625 marinas worldwide.

Blue flag beaches in Mexico 2013

Mexico’s five Blue Flag beaches (see map) are:

  • Chahué, Santa María de Huatulco, Oaxaca
  • Chileno, in Los Cabos, Baja California Sur
  • Delfines, in Cancún, Quintana Roo
  • El Palmar, in Zihuatanejo, Guerrero
  • Nuevo Vallarta Norte, on Banderas Bay in Nayarit

What does the Blue Flag system take into account?

The Blue Flag beach criteria are grouped into four main categories:

1. Environmental Education and Information

The beach must host at least 5 environmental education activities and display information about:

  • coastal zone ecosystems and natural, sensitive areas in the coastal zone
  • bathing water quality
  • the Blue Flag system
  • the code of conduct for the beach area

2. Water Quality

  • Water quality must be “excellent” in line with international standards
  • The beach must not receive any industrial or sewage-related discharges
  • Any nearby coral reefs must be monitored to ensure they remain healthy
  • Algae, seaweed, etc., should be left on the beach unless it adversely affects beach quality

3. Environmental Management

  • A beach management committee must conduct regular environmental audits
  • The beach must comply with coastal zone planning and environmental legislation
  • The beach must be clean, with sufficient waste disposal and recycling bins
  • There must be adequate and clean sanitary facilities
  • Regulations must prevent unauthorized camping, driving and dumping
  • Regulations concerning beach use by domestic animals must be enforced
  • Sustainable means of transportation must be promoted in the beach area

4. Safety and services

The beach must have:

  • first aid equipment and an adequate number of lifeguards and/or lifesaving equipment
  • a system to manage beach use and prevent conflicts and accidents
  • emergency plans to cover any unexpected pollution event
  • safe access to the beach and regular safety patrols
  • a supply of potable drinking water
  • access and toilets for persons with disabilities
  • a map showing the location of all facilities

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May 272013
 

Kudos to the Earth Island Institute for responding to the many criticisms we and others made of a blog article (“Water Pollution Plagues Mexico’s Scenic Pacific Coast”) by pulling it from their website. The following post has been edited to reflect that fact.

Water quality is a serious concern in many parts of Mexico and Geo-Mexico regularly includes short articles about the main issues as well as case studies related to water pollution (see “Related posts” below).

Ron Granich, a regular Geo-Mexico reader who lives in Pátzcuaro (Michoacán) and recognizes our keen interest in Mexico’s water quality kindly drew our attention to a recent article published on the website of the Earth Island Journal. Sadly, the blog article left much to be desired. The article was subtitled, “Tourists largely unaware that industrial pollution from rivers upstream is making them sick”, and attempted to argue that the pollution of Mexico’s Santiago River is a direct cause of the poor water quality of beach towns such as Sayulita.

The slight problem with this thesis is that the Santiago River flows nowhere near Sayulita and has no connection to the miniscule Sayulita River, far to its south (see map). There is no question that the Santiago is polluted. It collects serious pollutants from the major industrial area of El Salto (a short distance southeast of Guadalajara) and from Guadalajara, and from many smaller settlements along the way. More contaminants are added near its mouth, where the swampy delta has been transformed into productive fields, including tobacco plantations.

Main rivers of Western Mexico.

Map of the main rivers of Western Mexico. Credit: Tony Burton / Geo-Mexico; all rights reserved.

Pollution of the River Santiago is particularly evident at the Juanacatlán Falls near El Salto:

After the Juanacatlán Falls, the Santiago flows in a deep, steep-sided canyon for most of its course (which explains why no fewer than three major dams for hydro-electric power have been built along this stretch, including the one at La Yesca) before meandering across its delta to flow into the Pacific Ocean a short distance north of San Blas.

The Santiago River has no conceivable influence on the pollution levels in the rivers near Sayulita and San Francisco or indeed on beaches in their vicinity. This is not to say that those beaches are clean. The beaches of the Nayarit Riviera may indeed have high levels of Enterococcus spp, as we reported recently when looking at the murky world of water statistics in Mexico.

Note on clean water standards in Mexico and the USA:

It is sometimes argued that Mexico and the USA have different standards for what represents “clean water”. For marine (beach) environments, the U.S. limit is 35 Enterococci per 100 ml. of water, and is based on calculating a geometric mean of counts performed over a five week period. This method greatly reduces the impact of peak Enterococci counts. However, the Mexican limit of 100 Enterococci/100 ml. is based on a single sample maximum value. As explained in this US EPA technical document, Water Quality Standards for Coastal Recreation Waters: Using Single Sample Maximum Values in State Water Quality Standards, the two limits are approximately equivalent in terms of water quality. In other words, a geometric mean of 35 Enterococci/100 ml. means that the water is about as clean as a single maximum value of 100 Enterococci/100 ml.

Water quality IS a major concern in much of Mexico, and we applaud the Earth Island Institute for seeking to draw attention to the issues involved, and for their recent action in removing the original article, which helps to ensure that discussions of these issues are based on facts and not on misconceptions.

As always, we welcome discussion about this (and all our posts) via the comments feature. If the comments feature is not visible, simply click the title of the relevant post, and scroll down.

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How can Mexico City find sufficient water?

 Updates to Geo-Mexico  Comments Off on How can Mexico City find sufficient water?
May 202013
 

What happens if or when Mexico City needs more water than it is using at present? There are several options, depending on whether authorities choose to modify demand, supply, or both in order to improve the future situation.

In terms of managing (reducing) demand, conservation measures are one possibility. Changing consumer habits may require not only educational programs, but also usage tariffs that reflect the true costs of supply, and that encourage consumers to install water-saving devices and introduce water-saving practices in their daily lives. Demand would also be reduced if less water was lost through leakage. As mentioned in a previous post, in 2009, the National Water Commission (Conagua) estimated that a staggering 40% of potable water nationwide was being lost through leaks in city and municipal systems, with a further 20% not properly accounted for due to billing errors and clandestine connections.

Managing demand may be easier to achieve than managing supply, given that recent efforts to increase supply have met with concerted opposition from environmentalists and the people living in the areas from which water would be transferred to the city. In the last half of the twentieth century, while one political party (PRI) held power, it was possible for politicians to largely ignore the conflicts resulting from inter-basin transfers, arguing that their “solutions” served a national need. Now that local, state and federal politics are more contested, that approach is potential political suicide.

From a political perspective, the most acceptable source of additional water for Mexico City would probably be the recently identified deep aquifer described in Mexico’s major cities confront serious water supply issues. However, that discovery requires further research before its maximum sustainable yield can be determined or it can be brought into service.

Less politically acceptable are the various proposals to bring water from elsewhere to satisfy the thirst of Mexico City. One of the most frequently voiced suggestions is to add a fourth phase to the Cutzamala scheme (see Where does Mexico City get its water from?) to increase the amount of water it supplies by more than 25% to 24 m³/s. In addition, the plan would provide treatment for 42 m3/s of wastewater. This fourth phase, known as the Temascaltepec project (see map), would require the construction of a 120-meter-high, 740-meter-long dam on the Temascaltepec River to create a reservoir with a capacity of 65 million m³.

Map of the Cutzamala project

Map of the Cutzamala project. Click to enlarge.

Aqueducts and a 19-km-long tunnel would carry the water to the Valle de Bravo reservoir. The estimated cost would be $500 million. The Temascaltepec project is opposed by environmentalists and locals and is not likely to get under way any time soon. The residents of the villages near the proposed dam site are afraid that the project would cause their local springs to dry up and would adversely impact their farming of maize, sugar cane, banana, tomato, melon and peas.

To the south of Mexico City, an entirely different proposal is to bring water from the Amacuzac, Tecolutla and Atoyac Rivers, by damming the Amacuzac River, creating a 67 km2 reservoir (between the states of Morelos, Guerrero and Puebla) capable of storing 4,000 million cubic meters. Supplying Mexico City would require a 160 km long aqueduct, and would involve pumping water to a height of 1825 meters, requiring up to 5% of Mexico’s annual national electricity production. On the plus side, this could reduce the future abstraction of groundwater by as much as 50 m³/s.

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May 132013
 

Mexican rivers are not well suited for navigation and thus have had only a minor influence on Mexico’s historical development. Their most important use has been as sources of irrigation water and hydroelectric power. Mexico’s annual flow of river water (roughly 410 km3) is about 25% more than the St. Lawrence River, but 25% less than the Mississippi River. Most of this flow is in southern Mexico which gets by far the most rainfall. Mexico’s dams have an installed capacity of about 11 gigawatts of electricity, roughly one fifth of the country’s total generating capacity; they don’t operate at full capacity, so they only generate about one eighth of total electricity. Only about a fifth of the total river water is consumed for other productive purposes. This proportion is far higher for rivers in drier northern Mexico where river flow is significantly smaller during the dry winter months.

Fig 6-3 of Geo-Mexico: Rivers of Mexico

Fig 6-3 of Geo-Mexico: Rivers of Mexico; all rights reserved

The two longest rivers in Mexico, the Rio Bravo (Rio Grande north of the border) and Colorado, start in the US state of Colorado (see map). The Río Bravo is about 3000 km (1900 mi) long and forms the border between Mexico and the USA for about 2000 km (1250 mi). Occasionally floods shift its location resulting in border disputes. Though it drains about a quarter of Mexico’s total area, its drainage basin is arid and its total flow is less than 2% of Mexico’s total. The Colorado River, which is almost entirely in the USA, formed a vast delta in the otherwise arid Sonoran desert in northern Mexico. The amount of water reaching Mexico has declined dramatically as a result of the Hoover and Glen Canyon dams and other diversions in the USA (see here, here and here). As a result delta wetlands have been reduced to about 5% of their original extent, and the potential water supply for the rapidly-growing urban centers of Mexicali, Tijuana, Tecate and Rosarito has been compromised.

Interestingly, the Mexican river with the greatest flow, the Grijalva–Usumacinta, does not start in Mexico either (see map). The river has a double name because it is actually a double river, with two branches of similar length which both start in Guatemala. Each branch flows about 750 km (465 mi) through Chiapas before they unite in Tabasco about 25 km from the Gulf of Mexico. Each of the two branches has a flow of about 14% of Mexico’s total. The flow of the combined Grijalva–Usumacinta River is about twice that of the Missouri River in the USA.

There are several other important Mexican rivers. The Lerma River starts in the State of Mexico and flows westward into Lake Chapala and continues to the Pacific Ocean with the name Santiago. The Lerma–Santiago River system is about 1280 km (800 mi) long, the longest river entirely in Mexico. It drains about 6% of Mexico. The Lerma–Santiago, which flows through several states, is one of the economically most important rivers in Mexico because it feeds some of the country’s prime agricultural areas as well as the two largest metropolitan areas: Mexico City and Guadalajara. However, its flow is quite small, only about 2% of the national total.

The flow of the Balsas River, south of the Lerma–Santiago, is about three times that of the Lerma–Santiago. Though it offers some white-water rafting and irrigation opportunities, it is not as important economically. There are numerous rather long rivers that also flow west to the Pacific from the Western Sierra Madre in northwestern Mexico, but these have relatively little water. There are also several rather long rivers in the north such as the Nazas that flow into landlocked basins and either die or feed small drying lakes.

Three major rivers flow into the Gulf of Mexico through the state of Veracruz. The Rivers Papaloapan and Coatzacoalcos start in Oaxaca and flow through southern Veracruz. Their combined flow is nearly 20% of the national total. The Pánuco–Tamesi–Moctezuma River system starts in the State of Mexico and carries nearly 5% to the Gulf of Mexico at Tampico.

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Where does Mexico City get its water?

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May 092013
 

Mexico City is one of the world’s largest cities, and the metropolitan area of Greater Mexico City (map) extends well beyond the borders of the Federal District (Mexico City proper) into neighboring states, especially the State of Mexico.  The total population of Greater Mexico City is about 22 million, all of whom need safe access to water.

An old joke relates how engineers initially rejoiced at successfully draining the former lake on which Mexico City was built (something the Aztecs had tried, but failed to achieve), only to discover that the city now lacked any reliable source of fresh water for its inhabitants (something the Aztecs had successfully managed by building a system of aqueducts). Water has been a major issue for Mexico City ever since it was founded almost 700 years ago.

The Mexico City Metropolitan Area’s water supply is currently calculated to be around 82 m³/s. (The precise figure is unclear because many wells are reportedly unregistered). The main sources of water (and their approximate contributions to total water supply) are:

  • Abstraction of groundwater (73%)
  • Cutzamala system (18%)
  • Lerma system (6%)
  • Rivers and springs (3%)

In several previous posts we have looked at several issues arising from groundwater abstraction:

In this post we focus on the Cutzamala system (see graphic), one of Mexico’s most ambitious engineering feats of its time.

Cutzamala scheme

Cutzamala scheme (click to enlarge). Source: IMTA (1987)

The Cutzamala system supplies potable water to 11 boroughs (delegaciones) of the Federal District and 11 municipalities in the State of Mexico. The Cutzamala system is one of the largest water supply systems in the world, in terms of both the total quantity of water supplied (about 485 million cubic meters/yr) and in terms of the 1100 meters (3600 feet) difference in elevation that has to be overcome. The system cost about $1.3 billion, and was undertaken in three successive phases of construction, completed in 1982 (Villa Victoria dam), 1985 (incorporation of the Valle de Bravo and El Bosque dams, originally built in the 1940s and 1950s) and 1993 respectively.

As Cecillia Tortajada points out in Who Has Access to Water? Case Study of Mexico City Metropolitan Area, the investment of $1.3 billion was, at the time (1996), “higher than the national investment in the entire public sector in Mexico… in the areas of education ($700 million), health and social security ($400 million), agriculture, livestock and rural development ($105 million), tourism ($50 million), and marine sector ($60 million).”

The system includes 7 dams and reservoirs for storage, 6 major pumping stations (P.P. on the graphic) and a water purification plant. The volumes stored in the system are dependent on previous years’ rainfall. Water is transferred to the Valley of Mexico from more than 150 km away via reservoirs, pumping stations, open channels, tunnels, pipelines and aqueducts.

The Cutzamala system incorporates the Valle de Bravo and El Bosque dams, built originally as part of the “Miguel Alemán” project that generated hydro-electric power from the headwaters of the Cutzamala River (hence the name for the whole system). The reservoir at Valle de Bravo is an important resource for tourism and watersports. The hydro-electric power scheme is no longer functioning. The Cutzamala system has the capacity to supply up to 19 m³/s of water to the Valley of Mexico. In practice, it supplies almost 20% of the Valley of Mexico’s total water supply (usually quoted as being 82 m³/s).

The pumping required to lift water 1100 meters from the lowest storage point to the system’s highest point (from where gravity flow takes over) consumes a significant amount of energy, variously estimated at between 1.3 and 1.8 terawatt hours a year, equivalent to about 0.6% of Mexico’s total energy consumption, and representing a cost of about 65 million dollars/yr. This amount of electricity is claimed to be roughly equivalent to the annual energy consumption of the metropolitan area of Puebla (population 2.7 million).

The total operational costs for running the Cutzamala System are estimated at $130 million/yr. [all figures in US dollars]. Even operating at full capacity (19 m³/s or 600 million m³/yr), the approximate average cost of water would be $0.214/m³. The true costs are higher given that these calculations do not include the costs of treatment or distribution within the metropolitan area. The price charged to consumers averages about $0.20/m³.

The completion of the Cutzamala system involved resettling some villages. The plans included the construction of some 200 “social” projects to improve living conditions for the people most affected, including local potable water distribution systems, schools and roads. However, more than a decade after completion, there were still some unresolved conflicts concerning people forced to move, with many of them still claiming that they had received insufficient compensation.

Maintaining the Cutzamala system has been an on-going challenge. Most maintenance is scheduled for the Easter holiday period, when factories and offices close down and many Mexico City residents head for the beach, reducing demand for water. Since 1993, a parallel system of canals and pipelines has been built alongside the original system, allowing for sections of the old system to be shut down for maintenance, obviating the need to close the entire system whenever work is carried out.

Main sources:

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Apr 262013
 

An amendment to Mexico’s constitution in 2011 made access to potable water a basic human right, but Mexico’s major cities face unprecedented challenges in meeting future demands for drinking water. In this post we look at some of the water supply issues relating to Mexico City and Guadalajara.

In 2009, the National Water Commission (Conagua) estimated that a staggering 40% of potable water nationwide was being lost through leaks in city and municipal systems, with a further 20% not properly accounted for due to billing errors and clandestine connections. Conagua recently announced a new plan for Mexico City, that it hopes will safeguard that city’s water supply for the next 25 years. (OOSKAnews 18 April 2013)

The plan creates a new metropolitan decision-making body, which will be empowered to choose which sources of water will be used, set timelines and commitments, and monitor all activities carried out under the plan. Conagua head David Korenfeld said that establishing a single water management body for the entire metropolitan zone in the Valley of Mexico means that, “there exists no possibility of misinterpretation in collaboration”. At present, several different water management bodies have responsibility for different parts of the Metropolitan Area, which extends well beyond the boundaries of the Federal District (México D.F.) into the neighboring State of México (Estado de México).

Korenfeld argues that potable water prices must be related to the real costs of water production, system maintenance and service delivery, and that subsidies must be cut in order to achieve efficient, sustainable and equitable water management. According to Conagua data, water tariffs in the Valley of Mexico cover only  51% of the true costs of service provision.The new plan calls for the existing Cutzamala water system to be completely restructured, with an alternative channel created to bring water to the city.

sacm officeRamón Aguirre Díaz, the director of the Mexico City Water System (SACM) which would come under the new decision-making body, says that one of the main challenges is to ensure adequate water supply to the municipality of Iztapalapa. Iztapalapa is the most populous and fastest growing of the city districts, with over 90% of its territory urbanized. The SACM is suggesting a six-year, 150-million-dollar plan to resolve the situation, which would include waiving water charges for some areas where service has been poor and sporadic. Aguirre stressed the need for the government and society “to succeed in reducing water consumption and improve their habits”, saying that consumption needs to be cut by at least 30%.

Coincidentally, it is in Iztapalapa where the findings from several deep wells allowed Mexico City engineers and geologists to announce earlier this year that a 40-million-dollar study conducted over 18 months had identified a major new aquifer under Mexico City. The city has an average elevation of 2240 meters above sea level; the new aquifer, which could become a major new source of potable water, is located 2000 meters beneath the surface. The initial announcement claimed that the aquifer could supply as much as 80,000 liters of water a second.

Conagua officials cautioned that the potential usable flow of this aquifer still has to be confirmed and that it may take a further three years of research to establish the maximum sustainable yield.  The aquifer might indeed relieve Mexico City’s physical water scarcity (volumes of supply) at some point in the future, but it would not necessarily overcome the economic water scarcity (cost of supply) faced by many of its residents. (For more about economic water scarcity, see How fast is the ground sinking in Mexico City and what can be done about it?).

Frederick Mooser, arguably Mexico’s most distinguished geologist, was quoted in the press as saying that the indication of very large reserves of water below a depth of 1500 meters might well alleviate the continued need to extract water from aquifers closer to the surface, extraction that has caused so many problems for the city’s infrastructure. The major aquifer used currently lies at a depth of between 60 and 400 meters. There are about 630 wells in the Federal District alone; all are overexploited and have an average life expectancy of 30 years.

Mooser also pointed out that the results from the wells used to locate the new aquifer show that the area has considerable potential for geothermal power generation in the future.

Mexico’s second city, Guadalajara, also faces sever water management issues. According to a recent press report (OOSKAnews, 11 April 2013), Metropolitan Guadalajara loses 18% of its water through leaks in the supply system (a loss of around 41 million dollars in economic terms)

siapaAccording to an official from the city’s water utility, SIAPA, repairing ailing parts of the network (154 locations have been identified as “vulnerable”) could save most of the 4 million dollars a year currently being spent dealing with emergency repairs. However, the precise location of leaks is difficult to pinpoint because of a lack of metering equipment. In addition to the 18% lost through leaks, SIAPA believes another 12% goes unaccounted for as a result of clandestine connections and incorrect billing.

The biggest reason for leaks is the age of the system. Parts of the water supply networks in Mexico’s major cities are now over 70 years old. For example, in Guadalajara, more than 70% of the city’s 3458 km of main water supply lines is over 70 years old. Replacing the 2544 km of pipes older than 70 years would require investing around 300 million dollars, with a further 500 million dollars needed to upgrade the drainage system. SIAPA’s total investment in renewing and expanding systems is currently about 45 million dollars a year. The water firm is already said to be the most indebted decentralized public agency in the country, with debts of 240 million dollars.

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Two examples of Mexico-USA trans-border water pollution

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Aug 092012
 

In a previous post – Update on the severe drought in northern Mexico – we mentioned two cases where water was being transferred across the Mexico-USA border and where it was proving impossible to meet the terms of existing water treaties in the face of the severe drought in northern Mexico and the southern USA.

In this post, we look at two examples where the major trans-border concern is about water quality not quantity.

Case 1: The New River, California

The New River begins in Mexico as the Río Nuevo and receives agricultural runoff and industrial and domestic wastewater from the 1,000,000 or so residents of the metropolitan area of Mexicali, where a water treatment plant now operates. The New River then crosses the border northwards into California (west of the Colorado River) and flows into that state’s largest lake, the Salton Sea. The New River is about 130 kilometers long, with only the first 25 kilometers in Mexico.

The trans-border drainage basin of the New River

The trans-border drainage basin of the New River. Credit: IBWC.

The New River has a long history of high pollution levels, well documented in this Wikipedia entry: New River (Mexico – United States) and is possibly the most polluted river of its size anywhere in the USA. It is also one of the routes used by undocumented migrants entering the USA, as pointed out in this 2-minute video:

The California-Mexico Border Relations Council’s technical advisory committee recently announced a strategic plan to start cleaning up the polluted waters of the New River. In the Californian border city of Calexico, the plan calls for the installation of a 90-million-dollar water disinfection system and trash screens. Downstream, it also includes the creation of water-filtering wetlands in parts of the Imperial Valley, one of the USA’s most important agricultural areas. The strategic plan will also develop an integrated water quality monitoring and reporting program, so that changes in water quality can be quickly traced to source and any necessary cleanup measures can be implemented. The condition of the New River has been improving in the past decade, but much work remains to be done.

Case 2: Wastewater in Nogales, Arizona.

Further east along the border, Arizona state officials are suing the International Boundary and Water Commission (IBWC) for violations to the United States Clean Water Act, alleging that untreated Mexican industrial wastewater, mixed with domestic sewage, continues to cross the USA-Mexico border into the city of Nogales, Arizona. The suit claims that the wastewater has levels of cadmium, cyanide and ammoniacal nitrogen well above legal limits. The Arizona Department of Environmental Quality is demanding that the IBWC install an industrial waste treatment system at the Nogales International Wastewater Treatment Plant.

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Apr 092012
 

A recent report from researchers at the National Autonomous University of Mexico (UNAM) and the Metropolitan Autonomous University (UAM) confirms that the height of the water table below Mexico City is dropping by about one meter a year, as more water is pumped out of the aquifer than the natural replenishment rate from rainfall. About 60% of Mexico City’s drinking water comes from wells, with the remainder piped into the city, mainly via the Cutzamala system. The researchers say that up to 65% more water is taken from some parts of the Mexico City aquifer than the amount replaced each year by natural recharge.

As we reported in a previous post – Why are some parts of Mexico City sinking into the old lakebed? – this has resulted in parts of Mexico City sinking more than seven meters (23 ft) since 1891, with implications for water pipelines, drainage systems, building foundations and the city’s metro network, as well as an increased incidence of ground subsidence.

According to this latest research, the clay soil of the former lake bed below the city is sinking by between 6 and 28 cm/yr in most places, with rates in the southeast part of the city (where numerous wells have been drilled in recent years) sinking by up to 35 cm/yr.

How can the problem of sinking ground be resolved?

The report emphasizes the importance of conserving as much green space as possible within the city, to reduce runoff (and demands on the city’s drainage system) while simultaneously recharging aquifers. The three major alternatives, some combination of which is needed to resolve the problem are:

  • introduce more water-saving strategies so that demand does not continue to increase
  • bring more water from outside the Valley of Mexico (this would be costly and unpopular)
  • feed more wastewater back into the underground aquifers via “surface soaks”. As one example, the National Water Commission (Conagua) has announced plans to build a 200-million-dollar wastewater treatment plant (“El Caracol”) that will inject water back into the aquifer after treatment. It would be Mexico’s first ever large-scale reinjection project.

Perhaps not surprisingly, Mexico City residents pay more for their water than users anywhere else in the country, with an average water rate of US$1.23/cubic meter. Elsewhere, the two states sharing the arid Baja California Peninsula also have higher than average rates of $1.05/cubic meter (Baja California Sur) and $0.94/cubic meter (Baja California). The lowest rate in the country, well below the true cost of supplying water, is in Nayarit, and is just $0.25/cubic meter.

Within Mexico City, access to potable water is far from equally/fairly distributed across the city, as revealed by this thought-provoking quote :

In a study of water access in Mexico City, geographer Erik Swyngedouw found that “60 per cent of all urban potable water is distributed to three per cent of the households, whereas 50 per cent of the inhabitants make do on five per cent of the water”. Critical geographers like Swyngedouw ask us to take note of the spatial nature of power imbalances revealed in patterns of city design and growth: “mechanisms of exclusion… manifest the power relationships through which the geography of cities is shaped and transformed.”  [quote comes from page 31 of Nature’s Revenge: Reclaiming Sustainability in an Age of Corporate Globalization ; the reference is to Erik Swyngedouw’s Social Power and the Urbanization of Water: Flows of Power (OUP 2004).]

This grossly unequal distribution of potable water remains a critical problem that successive administrations in Mexico City and the surrounding State of México have done little to resolve.

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