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…

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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
Local fisherman sees his livelihood disappear. Credit: Vanguardia

Local fisherman sees his livelihood disappear. Credit: Vanguardia

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?

 Other, Updates to Geo-Mexico  Comments Off on Where does Mexico City get its water?
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

 Mexico's geography in the Press  Comments Off on Two examples of Mexico-USA trans-border water pollution
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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Aug 022012
 

The rainy season is now well underway in most of Mexico, but large swathes of the north are still experiencing severe drought conditions. For example, the state of Zacatecas was recently officially declared a drought disaster zone. It is still too early to estimate the total economic impact of the drought, but the U.S. Department of Agriculture (USDA) has reported that the drought has already caused agricultural damages in Mexico of $1.2 billion dollars, in addition to the $8 billion dollars of losses for Texas.

The drought has raised many issues connected to trans-border water agreements and flows, with renewed calls for them to be formally reviewed and updated. Two examples should suffice to show the seriousness of the situation.

1. Under the terms of a 1906 bilateral treaty, Mexico is entitled to 74 million cubic meters from the Elephant Butte and Caballo reservoirs in New Mexico. However, according to Adolfo Mata, foreign affairs officer for the U.S. Section of the International Boundary and Water Commission (IBWC), the USA will only be able to deliver a maximum of 18.5 million cubic meters this year.

2. Meanwhile, south of the border, the governor of the state of Chihuahua has stated that his state is unable to meet its obligation to deliver water to the USA under the terms of a 1944 International Water Treaty between the two countries. He said that, “No one can give what they do not have. Chihuahua cannot meet this treaty, not for a lack of will, but because it has not rained,” adding that Chihuahua was the only desert in the world that was expected to export water. According to the governor, the treaty requires that about 80% of the rainfall that Chihuahua receives is exported.

On a more positive note, researchers at the Ibero-American University have announced the development of a hydrogel capable of absorbing 200 times its own weight of water before gradually releasing it. The hydrogel could be a useful additional to the range of drought mitigation measures available for farmers. Climate change scientists predict that northern Mexico will suffer from more frequent and more severe droughts in coming decades.

The hydrogel, which is expected to cost 800 pesos (60 dollars) a kilo when it comes on the market, is a mix of natural gelatine and polyacrylic_acid  Hydrogel can only be used in orchards or other areas where the soil remains undisturbed by regular plowing, so it will not help farmers growing corn or beans, for example. The hydrogel has been tested in citrus orchards in San Luis Potosí, and succeeded in halving the required frequency of irrigation from twice a week to once a week, saving water and reducing energy costs. Each citrus tree required a kilo of hydrogel each year.

Previous posts related to the drought: