Water management in Greater Mexico City
Encyclopedia
Greater Mexico City
(Zona Metropolitana del Valle de México), a metropolitan area
with more than 19 million inhabitants including Mexico's capital
(Distrito Federal, or DF) with about 9 million inhabitants, faces tremendous water challenges. These include groundwater
overexploitation
, land subsidence
, the risk of major flooding, the impacts of increasing urbanization
, poor water quality, inefficient water use, a low share of wastewater treatment
, health concerns about the reuse of wastewater in agriculture, and limited cost recovery.
Overcoming these challenges is complicated by fragmented responsibilities for water management in Greater Mexico City:
Given the size and political importance of Greater Mexico City, a major flood or a major water supply interruption would be a national political crisis potentially threatening the stability of the federal government. The security of water supply and the functioning of the storm water drainage of the metropolitan area thus are major concerns for the local, state, district and federal governments.
In response to the challenges outlined above, the Federal Government, the State of Mexico and the Federal District initiated a US$2.8 billion Water Sustainability Program in 2007. In parallel, the government of the Federal District launched a Green Plan
which includes water conservation as an important element. Investments envisaged under both plans include an increase in wastewater treatment, the import of groundwater from irrigated areas North of the city where the groundwater table increased due to irrigation with wastewater, the construction of a major new storm water drainage tunnel, increased water imports from an expansion of the energy-intensive Cutzamala system that pumps water up over more than 1000 meters, and the reduction of non-revenue water
from 36% to 25%.
The climate of the Valley of Mexico
ranges from a semi-arid
belt in the north to a tropical one in the south. The valley receives about 700 millimetres (27.6 in) of annual rainfall, which is concentrated from June through to September/October with little or no precipitation during the remainder of the year. There are hardly any permanent rivers today; groundwater thus is the main water resource in the valley.
The valley has no natural drainage outlet for the waters that flow from the mountainsides, making the city vulnerable to flooding. It was artificially opened through the use of canals and tunnels starting in the 17th century, entirely draining what used to be Lake Texcoco
.
The rural southern portion of the Federal District and of the Valley of Mexico, in particular the Sierra Chichinautzin
is the most important natural recharge zone for the Mexico City Aquifer due to relatively high levels of precipitation and the high permeability of its basalt rock.
See also:Video Mexico faces water crisis as demand spirals of 30 November 2008 by Al Jazeera on YouTube about the protection of forests in the National Park around Popocatépetl.
Water supply and sanitation. The National Water Commission also supplies bulk water to the Federal District and to parts of Mexico state through the Cutzamala and Lerma systems.
In Mexico State, the State Water Commission buys bulk water from Conagua, transmits it through its own bulk water infrastructure and sells it on to 57 municipalities with 4.1 million inhabitants. The State Water Commission also monitors water quality, provides technical assistance to municipalities in water disinfection and sewer cleaning, operates wastewater pumping stations and five wastewater treatment plants, empties septic tanks and provides water in tankers in emergency situations. It also provides training and assists municipalities in the establishment of municipal utilities (organismos operadores). In the 59 municipalities of Mexico State and one municipality of the state of Hidalgo that are part of Greater Mexico City, each municipality is in charge of water supply and sanitation.
The municipal water utility of Mexico City, Sistema de Aguas de la Ciudad de México (SACM), is responsible for water supply and sanitation in the Federal District. Its head is appointed by the government of the District.
The water infrastructure in Greater Mexico City consists of infrastructure for bulk water supply and water distribution (water supply), wastewater collection, storm water collection and wastewater treatment (sanitation), and for irrigation using mainly wastewater.
), Metropolitan, East (or Texcoco
region) and North well fields.
Besides these well fields, the bulk water supply infrastructure of Greater Mexico city consists of two systems:Lerma and Cutzamala. The Lerma system, built in the 1940s, transfers 4.8 m3/s of water (6% of total water supply to Greater Mexico City) from well fields in the upper basin of the Lerma River in the West to Mexico City. The Cutzamala System built in stages from the late 1970s to the late 1990s to transfer 14.9 m3/s (19% of total supply) of water from the Cutzamala
River in the Balsas basin
in the Southwest to Greater Mexico City
for use as drinking water, lifting it over more than 1000 meters. It utilizes 7 reservoirs, a 127 km long aqueduct with 21 km of tunnels, 7.5 km open canal, and a water treatment plant. Its cost was US$ 1.3 billion. While providing Mexico City with over 20% of its water, the Cutzamala system currently operates at only 47% of its total capacity. Both systems are operated by the National Water Commission.
The water distribution system in the Federal District included nearly 11,000 kilometers of distribution lines and 243 storage tanks with a capacity of 1.5 million cubic meters in 1994. Water from all the separate sources is added to the common distribution system. The Federal District also operates a water transmission line (the Acueducto Periférico) that transports water from the Cutzamala System - entering the distribution system from the west - to the southern and eastern part of the district. The State of Mexico system has nearly 800 kilometers of distribution lines and 32 storage tanks with a capacity of 440,000 cubic meters. The State of Mexico operates the 49 kilometer water transmission line (the Macrocircuito) to transport water entering from the west side of the service area (including the imported water from the Cutzamala-Lerma System) to the east side. This transmission line is being upgraded to increase the volume of water taken from the Cutzamala-Lerma system to 7.3 cms, and to provide service to the eastern service area. The Macrocircuito is operated by the State Water Commission.
It is expected that the dependency of Mexico City on external sources of water will increase. Additionally, the absence of economic compensation mechanisms for those communities from which water is extracted has created conflicts among users and sometimes limits water transferred to the city.
The total dry weather flow for Greater Mexico City, which consists mainly of untreated municipal wastewater, was estimated at 44 m3/s in 1993. During the rainy season, the region experiences many storms of high intensity and short duration. A single storm can produce up to 70 millimeters (about 3 inches) of rainfall, representing 10 percent of the total annual precipitation. Because of this rainfall pattern, the general drainage system was designed to carry 200 m3/s over a 45 hour period
Until 1910 the Grand Canal functioned purely by gravity, with an inclination of 19 cm per km. Over the next five decades its inclination declined to 10 cm per km due to land subsidence of 7 meters. Several large pumps were installed in an attempt to maintain its capacity. After heavy floods in 1950 and 1951 it became clear that the Grand Canal could not protect the city any more from flooding and a deep drainage system (Drenaje profundo) was proposed for the first time. Studies on the system began in 1959; its construction began in 1967 and it was completed in 1975. It consists of a deep tunnel, the Emisor Central with a length of 68 km and a depth of up to 250m. It today constitutes by far the most important element of the Mexico City drainage system. It was designed for a flow of 170 m3/s. However, due to further land settlement the inclination in the Grand Canal became zero by 1990 and negative by 2000. Despite the installation of further pumps, the capacity of the Grand Canal thus declined from 80 m3/s in 1975 to 15 m3/s in 2008. This in turn affected the Emisor Central, which had been designed to be closed during the dry season for maintenance. Because of the settlement of the grand canal the Emisor Central was continuously filled with water, making it impossible to inspect it for problems or to maintain it, making maintenance impossible between 1995 and 2008. The tunnel has been damaged by overwork and corrosion of its 20 ft (6 m) diameter walls and its capacity has been reduced to 120 m3/s. In 2008 it was maintained for the first time in more than 12 years.
Overall, the combined discharge capacity of the system has declined from 280 m3/s in 1975 to 165 m3/s in 2008. The Nochistongo Channel is the only element of the system whose capacity remains undiminished at 30m3/s.
was treated in 2008, mostly in wastewater treatment plants in Mexico state. The treated wastewater is for local reuse projects such as ground water recharge and agricultural and urban-landscape irrigation. There were 13 wastewater treatment plants in the Federal District and 14 in the State of Mexico service area in 1994, treating a total flow of 2.62 and 1.69 m3/s respectively. The untreated portion of the wastewater is discharged to the drainage system, from where it is discharged to the North where it is being reused in irrigated agriculture.
Large-scale irrigation infrastructure was built in the state of Hidalgo to distribute storm water and wastewater from Mexico City for the irrigation of Alfalfa
as the main crop, as well as barley, wheat and corn. Thanks to the nutrients in the sewage, alfalfa yields are more than 100 tons per hectare, compared to the national average of 68-74 tons. Alfalfa is planted year-round, providing 9-10 harvests per planting, and is sold to livestock operations in other states. The infrastructure is operated and maintained by Irrigation districts No. 3 Tula and No. 100 Alfajayucan
in the Mezquital Valley. They used to be operated by Conagua, but were transferred to water user associations during the 1990s.
The cultivated area is 83,000 hectare
, about half the size of the U.S. state of Rhode Island. Wastewater has been used there since 1912. The wastewater, whether raw, partially treated or mixed with rainfall, is highly valued by the farmers because of its ability to improve soil quality and because of its nutrient load that allows increased productivity. However, the wastewater is contaminated with pathogenic organisms and toxic chemicals that constitute a health risk for both farmers and consumers of agricultural products.
Within the Federal District service area, in 1995 the 2.62 m3/s of treated reused wastewater is distributed as follows:
Recreational impoundments. A major wastewater reclamation and reuse scheme exists at Lake Texcoco
in conjunction with programs for flood control and dust abatement. Between flooding, the shallow, saline lake bed would dry and produce severe dust storms. In response to this problem, the Texcoco Plan was established in 1971. The solution was to create smaller, more permanent ponds within the large, intermittent lake bed, and to rehabilitate the problem areas for further urban and agricultural expansion through windbreaks, revegetation, agricultural irrigation, and drainage improvements. The artificial and more permanent lakes were created using lessons learned from the subsidence problem. High rates of pumping consolidated the clays and lowered the old lake bed by about 4 meters in places. The reuse component of the Texcoco plans include the construction of a facultative lagoon wastewater treatment system
, and reclamation of the collected storm water for agricultural irrigation. Thus, the potable water currently used for this purpose will be replaced.
Industrial reuse. Industries recycle and reuse wastewater generated by themselves or by municipalities. For example, 26 private companies in the Vallejo
area initiated a reuse program in 1989 by establishing a for-profit firm, Aguas Industriales de Vallejo. The firm rehabilitated an old municipal wastewater treatment plant and distributes reclaimed water to its shareholder companies at three-quarters of the cost of government supplied potable water.
Pilot project for potable reuse. The Federal District constructed two pilot treatment plants in 1983 to study the potential for the advanced wastewater treatment of secondary effluent for potable reuse, and to examine the potential for treating contaminated ground water. Based upon results of the experimental treatment plants, a new treatment facility was constructed, with a capacity of 0.3 m3/s, and designed for both ground water treatment and direct potable reuse. The established goal of the reuse project was to blend the reclaimed wastewater with treated ground water and add it directly into the distribution system Currently, the reclaimed wastewater is being used for non-potable purposes.
Floodwater. Artificial floodwater recharge has been practiced in the region since 1943, as a method to alleviate flooding rather than as a method to recharge groundwater. Early projects involved runoff retention and surface spreading, channel modification, and infiltration wells. Many of these projects were done in the highly permeable basalt of the upland areas and achieved very high rates of infiltration during periods of heavy rains. Artificial recharge of floodwater using injection wells was first developed in the Federal District around 1953. However, half of the wells were subsequently closed due to operational problems. In 1970, a series of approximately 56 wells was developed for the purposes of disposing of stormwater. These wells were capable of handling up to 35 m3/s of water collectively. Although the wells were not designed for recharge purposes, the storm water possibly reached the aquifer.
Treated wastewater. The Texcoco Project mentioned above has carried out studies on indirect potable reuse of reclaimed wastewater through artificial recharge of the aquifer using secondary and advanced treatment of municipal wastewater. The final effluent may be used in either infiltration ponds or injection wells. In a separate program carried out by the Federal District, a pilot plant injected advanced treated water directly into the aquifer at a rate of up to 0.05 m3/s. Monitoring wells were used to gauge changes in water quality and pressure levels.
, land subsidence
, the risk of major flooding, the impacts of increasing urbanization, poor water quality and intermittent supply, inefficient water use, a low share of wastewater treatment
, health concerns about the reuse of wastewater for irrigation, and limited cost recovery for water. Infrastructure coverage in terms of access to a piped water connection or to sanitation, which is used to monitor the Millennium Development Goals for water supply and sanitation, is almost universal in Greater Mexico City and as such does not constitute a challenge.
's exponential population growth has depleted its groundwater resources. Recharge of the aquifer
is about 31.6 m3/s compared to abstraction of 59.5 m3/s, resulting in an overdraft of about 28 m3/s. In 1983, systematic monitoring of the water levels in the aquifer began. Since that time, the average annual declines in ground water levels range from 0.1 to 1.5 meters per year in different zones. At the current rate of depletion, it has been calculated that the estimated volume of storage corresponds to between 200 and 350 times the annual abstraction. However, a simplistic water balance approach does not account for other realities. For example, the aquifer is vulnerable to geologically-induced water quality problems with increasing aquifer depth and consolidation and fracturing of clay layers. Furthermore, the actual volume available in the main aquifer would likely be less than estimated because of probable decreasing porosity with increasing depth. Also, there are practical, economic limits to the depth of pumping.
The water balance of Greater Mexico is as follows:
, residents are so accustomed to seeing a fetid sea of sewage rise in the streets that they have built miniature dikes in front of their homes. Flooding is caused both by the sinking together and increased soil impermeability due to urbanization. If the Emisor Central should fail during the rainy season, modelling shows that a major flood would occur that would inundate the historic center, the Mexico City International Airport
and the eastern boroughs of Mexico City.
has now been reversed due to groundwater depletion. The Groundwater under Mexico City thus is believed to be increasingly vulnerable to contaminants from waste dumps and industrial sites leaching to the aquifer. Furthermore, the deep drainage system penetrates below the clay aquitard in some places into the main aquifer. During periods of heavy rain, wastewater seeps out from the deep tunnels into the surrounding subsoil contaminating the aquifer.
Leaks in the distribution system are a major cause of concern for drinking water quality. When the soil is permeated by sewage from leaking sewers or from other sources, then leaky pipelines will be infiltrated with contaminated water when pressure is low. According to the Federal District's water quality laboratory, neighborhoods that experience more frequent interruptions in service have poorer quality water compared to neighborhoods with a constant supply. The percent of household tap samples in compliance with the residual chlorine standard (0.2 milligrams/liter) ranged from 87 to 100 percent in tests undertaken in 1993 and was notably low among southeastern counties (Iztapalapa
, Tláhuac
, and Xochimilco
). Household water storage tanks, or tinácos, are common on almost all household rooftops and are used to store water when water pressure in the system is inadequate. In many instances, the tanks are open and not cleaned regularly, permitting the residual chlorine to dissipate and encouraging the growth of microorganisms. The standard levels of chlorine (0.2 milligrams/liters) maintained in the distribution system as it reaches the customer's tap are not sufficient to inactivate microorganisms that may have entered the pipelines.
Intermittent supply. Water supply in many parts of Greater Mexico City is intermittent and pressure is often insufficient. Users thus have to complement their water supply with water bought from tanker trucks, or pipas. Occasionally, water supply is even cut for several days, as it occurred in January 2009 when the water supply from the Cutzamala system had to be reduced cutting water to 5.5 million people for three days. This incident was followed by a second supply cut in March 2009, and most recently a third cut in April 2009. This third cut was done in response to alarmingly low levels in the city's water reserves, and reparations being undertaken on the Cutzamala system. It lasted 36 hours, and left over five million city residents without water services. In response, the Mexico City government has had to implement an emergency supply response program, providing water in tanker trucks and bottles to residents of the affected communities.
There are concerns about the health and environmental impacts of the reuse of untreated wastewater from Mexico City for irrigation. Crops to be grown using wastewater are restricted to crops not eaten raw, but these restrictions are difficult to enforce and farmers also grow vegetables using wastewater. According to a study by the International Water Management Institute
(IWMI), these risks need to be carefully considered, but the importance of this practice for the livelihoods of countless smallholders must also be taken into account. Studies on soils irrigated with untreated wastewater for 50 years show an accumulation of heavy metals in the soil, but also that they accumulated in plants to a lower extent. Another study found bacterial contamination of canal water used for bathing and of groundwater used for drinking water supply in the irrigated areas where wastewater was being reused, resulting in a high incidence of diarrhea and skin irriations.
of 40%, close to the Mexican average, meaning that only 60% of the water pumped into the system is actually being billed for. A large share of non-revenue water is due not to leakage, but to illegal connections. Furthermore, SACM, the water department of the District, has by far the lowest collection efficiency among the 25 major municipalities, with only 40% of all bills being paid. Thus only 24% (60% is being billed, 40% of the bills being paid) of the water pumped into the system is being paid for. The level of non-revenue water in Mexico State is lower, so that the average level in the metropolitan area is 36%.
Per capita water use figures are difficult to compare over time, because sources typically do not indicate if water losses are included in the figures or not. The National Statistical Institute gives water use in the Federal District at 223 liter/day in 1999 (probably after losses), including 164 liter of residential use and 59 liter for industrial and commercial uses. This is only about one third of average water use in the United States
, which is 603 liter/capita/day. However, it is still one third higher than water use in France
, which is only 165 liter/capita/day. Another source gives average per capita water use in 1994 as 364 and 230 liters per day for the Federal District and Mexico State respectively (probably before losses). Authorities attribute the larger per capita use in the Federal District to the fact that the Federal District is more developed and includes more commercial and industrial activity than the State of Mexico. However, lower tariffs and lower metering in the Federal District may also influence the higher water use.
s from the Lerma
and Balsas
basins, and what is recovered from users. Reasons for low cost recovery include illegal water connections, low tariffs and poor bill collection, in particular in the Federal District
.
Cost recovery in Mexico State is much higher than in the Federal District. For example, the city of Toluca
in Mexico State charges residential users 9.5 pesos (US$0.72)/m3 for a consumption of 30m3, including a sanitation surcharge, the sixth-highest among the country’s 25 major municipalities. This still falls short of the cost of bulk water from the Cutzamala system at nearly 10 pesos (US$0.78)/m3, without taking into account the cost of distributing water and of sanitation.
In 2004 the Federal District charged residential users 3.3 pesos (US$0.26)/m3 for the same consumption without any surcharge for sanitation, the fourth-lowest among the same municipalities. The remainder is effectively subsidized by the municipal and federal governments. In August 2007 a conflict had erupted between Conagua and the Federal District when Conagua increased the tariff for water supplied through the Cutzamala system and the District refused to accept the increase.
that also includes drainage and wastewater treatment. In addition it emphasizes water conservation and water reuse through aquifer recharge. Both plans aim at reducing non-revenue water
.
launched a US$2.8 billion Water Sustainability Program for the Valley of Mexico through 2012. The program amplifies the earlier Program for the Sanitation of the Valley of Mexico. Its objectives are to avoid major floods such as the 2007 Tabasco flood
, to treat all the wastewater collected, and to reduce groundwater overexploitation.
Water supply and exchange. 14 m3/s more water would be mobilized from various sources. The largest of these imports (5 m3/s) will consist of groundwater from the Tula Valley North of Greater Mexico, where the groundwater table has increased from many years of irrigation with untreated wastewater, at a cost of US$255 million. The second-largest source of additional water will be mobilized through an exchange of treated wastewater for clean water at present used for irrigation in the Vaso del Christo area (4m3/s), at a cost of 140 million. As part of the "rehabilitation" of existing sources, the Cutzamala system is expected to be expanded by 3 m3/s, at a cost of US$275 million. Finally, 2 m3/s would be made available from the Guadelupe dam in Mexico state at a cost of US$40 million.
Storm water drainage and wastewater treatment. The program foresees the construction of the Emisor Oriente in parallel to the Emisor Central. In February 2009, Conagua oversaw the purchase of the first of three underground drills from German firm Herrenknecht. The new drill will be used to begin excavations for the tunnel in April 2009. All works on the tunnel system are expected to be completed in September 2012, at an expected cost of MXP 13 billion (approx. USD 1 billion).
Out of the discharge of the Emisor Oriental 23 m3/s would be treated in a planned wastewater treatment plant in El Salto
in Hidalgo State to deliver water to the Tula Irrigation District. Almost half of the investment (US$1.28 bn) will be for the construction of 6 wastewater treatment plants, the largest of which by far would be the Atotonilco (El Salto) plant. The US$900m contract to finance, build and operate the plant, allegedly the largest wastewater treatment plant in the world with a maximum capacity of 4.3 million cubic meter/day, was awarded in 2011 to a consortium led by the Spanish company Acciona.
The achievement of the program objective to both supply a growing population with water and to reduce pressure on the aquifer rests on the assumption that leakage will be reduced from 36% in 2005 to 25% in 2030.
Financing. The program is being financed from the following sources:
Complementing the SARP, the Federal District launched in 2007 a 15-year Green Plan
(Plan Verde) that aims at the sustainable development of the District along seven major axes, one of which is water. In 2008 it had a budget of US$6 million. Concerning water, it foresees reaching an equilibrium in the aquifer, reducing residential water use, reducing network losses, increasing the reuse and the treatment of wastewater, and the creation of parks around the lakes Tláhuac
and Xochimilco
. More specifically, it foresees increased aquifer recharge through changes in land use and recharge wells; the metering
of all users by 2010 and making all users pay for water; identify and regularize illegal connections; the construction of tertiary wastewater treatment plants for the injection of treated wastewater into the aquifer
. The Plan is expected to relieve pressure on the aquifer by 6.8 m3/s, including 3.3 m3/s by reducing leakage, 1 m3/s through water conservation and 2.5 m3/s by recharging groundwater with treated wastewater. These measures together, if successful, would reduce groundwater abstraction in Greater Mexico by 10% and the overdraft by 25%, and thus still fall short from establishing an equilibrium between abstraction and recharge.
. A total of four concession covering 11 of the District's 16 delegaciones would be bid out. The concessions would replace the existing four service contracts for metering and billing.
, the Head of Government of the Federal District
from 1988 to 1997 who was appointed by President Carlos Salinas
(PRI), led the process of private sector participation in water supply in Mexico City in the early 1990s. At that time water revenues were extremely low, there was no functioning customer database, virtually no metering, and low bill collection efficiency. At least 22% of customers did not receive bills at all, partly because water connections were carried out by one department and billing by another which did not receive any information about water connections from the former.
In November 1992 bids were launched, in March 1993 the results were announced and in November 10-year service contracts were signed with four firms, each for one block of the capital:
The process of private sector participation foresaw three phases:
The city remained in charge of the water production, treatment and main distribution infrastructure, as well as some aspects of collection and the sanitation infrastructure. It also set water tarirfs. The first two phases were successful. Under the contracts the number of metered connections increased from virtually none in 1994 to up to 1,264,500 in 2002, reaching more than 90% of all users. The third phase, however, was less successful.
Between 1994 and 1998 the amount billed increased by almost 30% in real terms. But the amount collected stagnated, since private operators were not in charge of bill collection. Collection efficiency actually declined from 84% to 69% The service itself remained unchanged in terms of intermittency of supply and water quality, since these aspects were not part of the contracts. Tariffs and cost recovery also remained unchanged, with revenues covering less than 75% of operating costs. The third phase of turning over increased responsibility to the private sector was abandoned after the PRD won elections in 1997 and renegotiated the contracts.
The PRD mayor Andrés Manuel López Obrador
(2000–2005) renewed the contracts in 2004 for another five years,. His successor Alejandro Encinas Rodríguez
initially announced that the District would terminate the contracts even before they expired, but his successor Marcelo Ebrard
actually extended them for another year until mid-2010.
(IDB) approved a US$365 million loan for the Valley of Mexico Sanitation Project, in parallel with a loan of US$410 million by the Overseas Economic Cooperation Fund
of Japan. The IDB project, which closed in 2005, foresaw the construction of 4 wastewater treatment plants with a total capacity of 74.5 m3/s as well as the rehabilitation of drainage systems.
Greater Mexico City
Greater Mexico City refers to the conurbation around Mexico City, officially called Mexico City Metropolitan Area , constituted by the Federal District—itself composed of 16 boroughs—and 41 adjacent municipalities of the states of Mexico and Hidalgo...
(Zona Metropolitana del Valle de México), a metropolitan area
Metropolitan area
The term metropolitan area refers to a region consisting of a densely populated urban core and its less-populated surrounding territories, sharing industry, infrastructure, and housing. A metropolitan area usually encompasses multiple jurisdictions and municipalities: neighborhoods, townships,...
with more than 19 million inhabitants including Mexico's capital
Mexico City
Mexico City is the Federal District , capital of Mexico and seat of the federal powers of the Mexican Union. It is a federal entity within Mexico which is not part of any one of the 31 Mexican states but belongs to the federation as a whole...
(Distrito Federal, or DF) with about 9 million inhabitants, faces tremendous water challenges. These include groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
overexploitation
Overexploitation
Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Sustained overexploitation can lead to the destruction of the resource...
, land subsidence
Groundwater-related subsidence
Groundwater-related subsidence is the subsidence of land resulting from groundwater extraction, and a major problem in the developing world as major metropolises swell without adequate regulation and enforcement, as well as a being a common problem in the developed world...
, the risk of major flooding, the impacts of increasing urbanization
Urbanization
Urbanization, urbanisation or urban drift is the physical growth of urban areas as a result of global change. The United Nations projected that half of the world's population would live in urban areas at the end of 2008....
, poor water quality, inefficient water use, a low share of wastewater treatment
Wastewater Treatment
Wastewater treatment may refer to:* Sewage treatment* Industrial wastewater treatment...
, health concerns about the reuse of wastewater in agriculture, and limited cost recovery.
Overcoming these challenges is complicated by fragmented responsibilities for water management in Greater Mexico City:
- The Federal government under President Felipe CalderónFelipe CalderónFelipe de Jesús Calderón Hinojosa is the current President of Mexico. He assumed office on December 1, 2006, and was elected for a single six-year term through 2012...
of the National Action PartyNational Action Party (Mexico)The National Action Party , is one of the three main political parties in Mexico. The party's political platform is generally considered Centre-Right in the Mexican political spectrum. Since 2000, the President of Mexico has been a member of this party; both houses have PAN pluralities, but the...
(PAN) is in charge of regulating the use of water resources, contributing to the financing of investments and supplying bulk water from other basins through the National Water Commission Conagua; - The State of Mexico under governor Enrique Peña NietoEnrique Peña NietoEnrique Peña Nieto is a Mexican politician. A member of the Institutional Revolutionary Party , he served as governor of the State of Mexico from 2005 to 2011. On September 19, 2011, he announced his candidacy in the 2012 Mexican presidential election to succeed Felipe Calderón...
of the Institutional Revolutionary PartyInstitutional Revolutionary PartyThe Institutional Revolutionary Party is a Mexican political party that held power in the country—under a succession of names—for more than 70 years. The PRI is a member of the Socialist International, as is the rival Party of the Democratic Revolution , making Mexico one of the few...
(PRI) provides bulk water, treats wastewater and assists municipalities in providing water and sanitation services in its part of Greater Mexico City; - 59 municipal governments in the part of Greater Mexico City located in the State of Mexico and one municipality in Hidalgo State are in charge of water distribution and sanitation for their constituents;
- the government of Federal District mayor Marcelo EbrardMarcelo EbrardMarcelo Luis Ebrard Casaubón is the current Head of Government of the Federal District since December 5, 2006. He is a Mexican politician affiliated to the Party of the Democratic Revolution who served as Secretary-General of the former Mexican Federal District Department, minister of public...
of the Party of the Democratic RevolutionParty of the Democratic RevolutionThe Party of the Democratic Revolution is a democratic socialist party in Mexico and one of 2 Mexican affiliates of the Socialist International...
(PRD) provides water supply and sanitation services to its constituents through its water department; and - two irrigation districts in Hidalgo state are in charge of irrigation with wastewater from Greater Mexico City.
Given the size and political importance of Greater Mexico City, a major flood or a major water supply interruption would be a national political crisis potentially threatening the stability of the federal government. The security of water supply and the functioning of the storm water drainage of the metropolitan area thus are major concerns for the local, state, district and federal governments.
In response to the challenges outlined above, the Federal Government, the State of Mexico and the Federal District initiated a US$2.8 billion Water Sustainability Program in 2007. In parallel, the government of the Federal District launched a Green Plan
Green Plan
Green Plans are comprehensive management plans that have the final goal of achieving environmental and economic sustainability. They are integrated, all-inclusive strategies that replace traditional single-issue policies. Green Plans have been implemented in several regions of the world including...
which includes water conservation as an important element. Investments envisaged under both plans include an increase in wastewater treatment, the import of groundwater from irrigated areas North of the city where the groundwater table increased due to irrigation with wastewater, the construction of a major new storm water drainage tunnel, increased water imports from an expansion of the energy-intensive Cutzamala system that pumps water up over more than 1000 meters, and the reduction of non-revenue water
Non-revenue water
Non revenue water is water that has been produced and is “lost” before it reaches the customer. Losses can be real losses or apparent losses . High levels of NRW are detrimental to the financial viability of water utilities, as well to the quality of water itself...
from 36% to 25%.
Geography and climate
Valley of Mexico
The Valley of Mexico is a highlands plateau in central Mexico roughly coterminous with the present-day Distrito Federal and the eastern half of the State of Mexico. Surrounded by mountains and volcanoes, the Valley of Mexico was a centre for several pre-Columbian civilizations, including...
ranges from a semi-arid
Semi-arid
A semi-arid climate or steppe climate describes climatic regions that receive precipitation below potential evapotranspiration, but not extremely...
belt in the north to a tropical one in the south. The valley receives about 700 millimetres (27.6 in) of annual rainfall, which is concentrated from June through to September/October with little or no precipitation during the remainder of the year. There are hardly any permanent rivers today; groundwater thus is the main water resource in the valley.
The valley has no natural drainage outlet for the waters that flow from the mountainsides, making the city vulnerable to flooding. It was artificially opened through the use of canals and tunnels starting in the 17th century, entirely draining what used to be Lake Texcoco
Lake Texcoco
Lake Texcoco was a natural lake formation within the Valley of Mexico. The Aztecs built the city of Tenochtitlan on an island in the lake. The Spaniards built Mexico City over Tenochtitlan...
.
The rural southern portion of the Federal District and of the Valley of Mexico, in particular the Sierra Chichinautzin
Sierra Chichinautzin
The Sierra Chichinautzin volcanic field is located in the Trans-Mexican Volcanic Belt, approximately 350 km from where the Cocos plate subducts beneath the North American plate. According to The Smithsonian Institution's Global Volcanism Program, "The massive Chichinautzin volcanic field...
is the most important natural recharge zone for the Mexico City Aquifer due to relatively high levels of precipitation and the high permeability of its basalt rock.
See also:Video Mexico faces water crisis as demand spirals of 30 November 2008 by Al Jazeera on YouTube about the protection of forests in the National Park around Popocatépetl.
Sector responsibilities
Water resources management. The National Water Commission (Conagua) is responsible for water resources management in Mexico, including granting of water abstraction and wastewater discharge permits.Water supply and sanitation. The National Water Commission also supplies bulk water to the Federal District and to parts of Mexico state through the Cutzamala and Lerma systems.
In Mexico State, the State Water Commission buys bulk water from Conagua, transmits it through its own bulk water infrastructure and sells it on to 57 municipalities with 4.1 million inhabitants. The State Water Commission also monitors water quality, provides technical assistance to municipalities in water disinfection and sewer cleaning, operates wastewater pumping stations and five wastewater treatment plants, empties septic tanks and provides water in tankers in emergency situations. It also provides training and assists municipalities in the establishment of municipal utilities (organismos operadores). In the 59 municipalities of Mexico State and one municipality of the state of Hidalgo that are part of Greater Mexico City, each municipality is in charge of water supply and sanitation.
The municipal water utility of Mexico City, Sistema de Aguas de la Ciudad de México (SACM), is responsible for water supply and sanitation in the Federal District. Its head is appointed by the government of the District.
Infrastructure
Water supply
The Federal District and State of Mexico combined had 1,089 registered wells at depths of 70 to 200 meters in 1994. This does not include wells operated by the National Water Commission, which are deeper. There are also a large number of non-registered wells, many of which are located in the State of Mexico. Wells are generally located in four different well fields. These are labeled as South (or XochimilcoXochimilco
Xochimilco is one of the sixteen delegaciones or boroughs within Mexican Federal District. The borough is centered on the formerly independent city of Xochimilco, which was established on what was the southern shore of Lake Xochimilco in the pre-Hispanic period...
), Metropolitan, East (or Texcoco
Texcoco, Mexico State
Texcoco is a city and municipality located in the northeast portion of Mexico State, 25 km northeast of Mexico City. In the pre-Hispanic era, this was a major Aztec city on the shores of Lake Texcoco. After the Conquest, the city was initially the second most important after Mexico City,...
region) and North well fields.
Besides these well fields, the bulk water supply infrastructure of Greater Mexico city consists of two systems:Lerma and Cutzamala. The Lerma system, built in the 1940s, transfers 4.8 m3/s of water (6% of total water supply to Greater Mexico City) from well fields in the upper basin of the Lerma River in the West to Mexico City. The Cutzamala System built in stages from the late 1970s to the late 1990s to transfer 14.9 m3/s (19% of total supply) of water from the Cutzamala
Cutzamala
Cutzamala may refer to:*Cutzamala de Pinzón, municipality and township in the state of Guerrero, Mexico*Cutzamala , a pre-Columbian Mesoamerican archaeological site, a fortified garrison settlement in the Postclassic-era Tarascan state...
River in the Balsas basin
Balsas River
The Balsas River is a major river of south-central Mexico. The basin flows through the states of Puebla, Morelos, Guerrero, and Mexico. The river empties into the Pacific Ocean at Mangrove Point, adjacent to the city of Lázaro Cárdenas, Michoacán...
in the Southwest to Greater Mexico City
Greater Mexico City
Greater Mexico City refers to the conurbation around Mexico City, officially called Mexico City Metropolitan Area , constituted by the Federal District—itself composed of 16 boroughs—and 41 adjacent municipalities of the states of Mexico and Hidalgo...
for use as drinking water, lifting it over more than 1000 meters. It utilizes 7 reservoirs, a 127 km long aqueduct with 21 km of tunnels, 7.5 km open canal, and a water treatment plant. Its cost was US$ 1.3 billion. While providing Mexico City with over 20% of its water, the Cutzamala system currently operates at only 47% of its total capacity. Both systems are operated by the National Water Commission.
The water distribution system in the Federal District included nearly 11,000 kilometers of distribution lines and 243 storage tanks with a capacity of 1.5 million cubic meters in 1994. Water from all the separate sources is added to the common distribution system. The Federal District also operates a water transmission line (the Acueducto Periférico) that transports water from the Cutzamala System - entering the distribution system from the west - to the southern and eastern part of the district. The State of Mexico system has nearly 800 kilometers of distribution lines and 32 storage tanks with a capacity of 440,000 cubic meters. The State of Mexico operates the 49 kilometer water transmission line (the Macrocircuito) to transport water entering from the west side of the service area (including the imported water from the Cutzamala-Lerma System) to the east side. This transmission line is being upgraded to increase the volume of water taken from the Cutzamala-Lerma system to 7.3 cms, and to provide service to the eastern service area. The Macrocircuito is operated by the State Water Commission.
It is expected that the dependency of Mexico City on external sources of water will increase. Additionally, the absence of economic compensation mechanisms for those communities from which water is extracted has created conflicts among users and sometimes limits water transferred to the city.
Combined sewer system
Greater Mexico City is served by a singled combined sewer system, collecting municipal wastewater, industrial wastewater and storm water. It includes 7400 mile of pipes,, 68 pumping stations, numerous dams, lagoons, and regulatory tanks for flow control, 111 kilometers of open canals, 42 kilometers of rivers (rio) used primarily for drainage, and 118 kilometers of underground collectors (interceptor and emisor) and tunnels. The three interceptors are:- The Western Interceptor (Interceptor del Poniente), draining into the Nochistongo Channel, which ultimately joins the Emisor Central;
- The Central Interceptor (Interceptor Central), draining into the Emisor Central (Drenaje Profundo) and then into the Salto River in Hidalgo state near the Requena dam, from where it flows to the Mezquital valley; and
- The Eastern Interceptor (Interceptor del Oriente), draining into the Grand Canal, then into the old and new tunnels of TequixquiacTequixquiacSantiago Tequixquiac is the seat of the municipality of Tequixquiac located in the northeastern part of the state of Mexico in Mexico, although both are commonly called Tequixquiac. The town is located at a northern pass leading out of the Valley of Mexico and about 120 km northeast of the...
and ultimately to the Salado River.
The total dry weather flow for Greater Mexico City, which consists mainly of untreated municipal wastewater, was estimated at 44 m3/s in 1993. During the rainy season, the region experiences many storms of high intensity and short duration. A single storm can produce up to 70 millimeters (about 3 inches) of rainfall, representing 10 percent of the total annual precipitation. Because of this rainfall pattern, the general drainage system was designed to carry 200 m3/s over a 45 hour period
Until 1910 the Grand Canal functioned purely by gravity, with an inclination of 19 cm per km. Over the next five decades its inclination declined to 10 cm per km due to land subsidence of 7 meters. Several large pumps were installed in an attempt to maintain its capacity. After heavy floods in 1950 and 1951 it became clear that the Grand Canal could not protect the city any more from flooding and a deep drainage system (Drenaje profundo) was proposed for the first time. Studies on the system began in 1959; its construction began in 1967 and it was completed in 1975. It consists of a deep tunnel, the Emisor Central with a length of 68 km and a depth of up to 250m. It today constitutes by far the most important element of the Mexico City drainage system. It was designed for a flow of 170 m3/s. However, due to further land settlement the inclination in the Grand Canal became zero by 1990 and negative by 2000. Despite the installation of further pumps, the capacity of the Grand Canal thus declined from 80 m3/s in 1975 to 15 m3/s in 2008. This in turn affected the Emisor Central, which had been designed to be closed during the dry season for maintenance. Because of the settlement of the grand canal the Emisor Central was continuously filled with water, making it impossible to inspect it for problems or to maintain it, making maintenance impossible between 1995 and 2008. The tunnel has been damaged by overwork and corrosion of its 20 ft (6 m) diameter walls and its capacity has been reduced to 120 m3/s. In 2008 it was maintained for the first time in more than 12 years.
Overall, the combined discharge capacity of the system has declined from 280 m3/s in 1975 to 165 m3/s in 2008. The Nochistongo Channel is the only element of the system whose capacity remains undiminished at 30m3/s.
Wastewater treatment
Only about 15% of the wastewater collected in Greater Mexico CityGreater Mexico City
Greater Mexico City refers to the conurbation around Mexico City, officially called Mexico City Metropolitan Area , constituted by the Federal District—itself composed of 16 boroughs—and 41 adjacent municipalities of the states of Mexico and Hidalgo...
was treated in 2008, mostly in wastewater treatment plants in Mexico state. The treated wastewater is for local reuse projects such as ground water recharge and agricultural and urban-landscape irrigation. There were 13 wastewater treatment plants in the Federal District and 14 in the State of Mexico service area in 1994, treating a total flow of 2.62 and 1.69 m3/s respectively. The untreated portion of the wastewater is discharged to the drainage system, from where it is discharged to the North where it is being reused in irrigated agriculture.
Reuse in irrigated agriculture
Alfalfa
Alfalfa is a flowering plant in the pea family Fabaceae cultivated as an important forage crop in the US, Canada, Argentina, France, Australia, the Middle East, South Africa, and many other countries. It is known as lucerne in the UK, France, Australia, South Africa and New Zealand, and known as...
as the main crop, as well as barley, wheat and corn. Thanks to the nutrients in the sewage, alfalfa yields are more than 100 tons per hectare, compared to the national average of 68-74 tons. Alfalfa is planted year-round, providing 9-10 harvests per planting, and is sold to livestock operations in other states. The infrastructure is operated and maintained by Irrigation districts No. 3 Tula and No. 100 Alfajayucan
Alfajayucan
Alfajayucan is a town and one of the 84 municipalities of Hidalgo, in central-eastern Mexico. The municipal seat lies at Alfajayucan. The municipality covers an area of 467.7 km².As of 2005, the municipality had a total population of 16,859....
in the Mezquital Valley. They used to be operated by Conagua, but were transferred to water user associations during the 1990s.
The cultivated area is 83,000 hectare
Hectare
The hectare is a metric unit of area defined as 10,000 square metres , and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare was thus 100 ares or 1/100 km2...
, about half the size of the U.S. state of Rhode Island. Wastewater has been used there since 1912. The wastewater, whether raw, partially treated or mixed with rainfall, is highly valued by the farmers because of its ability to improve soil quality and because of its nutrient load that allows increased productivity. However, the wastewater is contaminated with pathogenic organisms and toxic chemicals that constitute a health risk for both farmers and consumers of agricultural products.
Reuse for other purposes
Water reuse activities in Greater Mexico City officially began in 1984 under the National Program for Efficient Use of Water. This national program included the establishment of new wastewater discharge regulations by the Federal District, and in 1990, provisions were established for an industrial pretreatment program - an important prerequisite for any reclamation and reuse activity. However, little information is available on the extent and success of industrial pretreatment programs.Within the Federal District service area, in 1995 the 2.62 m3/s of treated reused wastewater is distributed as follows:
- 83 percent for urban landscape irrigation and recreational impoundments,
- 10 percent for industrial uses,
- 5 percent for agricultural irrigation, and
- 2 percent for commercial uses such as car washing.
Recreational impoundments. A major wastewater reclamation and reuse scheme exists at Lake Texcoco
Lake Texcoco
Lake Texcoco was a natural lake formation within the Valley of Mexico. The Aztecs built the city of Tenochtitlan on an island in the lake. The Spaniards built Mexico City over Tenochtitlan...
in conjunction with programs for flood control and dust abatement. Between flooding, the shallow, saline lake bed would dry and produce severe dust storms. In response to this problem, the Texcoco Plan was established in 1971. The solution was to create smaller, more permanent ponds within the large, intermittent lake bed, and to rehabilitate the problem areas for further urban and agricultural expansion through windbreaks, revegetation, agricultural irrigation, and drainage improvements. The artificial and more permanent lakes were created using lessons learned from the subsidence problem. High rates of pumping consolidated the clays and lowered the old lake bed by about 4 meters in places. The reuse component of the Texcoco plans include the construction of a facultative lagoon wastewater treatment system
Stabilization pond
Stabilization pond technology - sometimes also called facultative pond technology - is a natural method for wastewater treatment.-Technology:Stabilization ponds consist of shallow man-made basins comprising a single or several series of anaerobic, facultative or maturation ponds...
, and reclamation of the collected storm water for agricultural irrigation. Thus, the potable water currently used for this purpose will be replaced.
Industrial reuse. Industries recycle and reuse wastewater generated by themselves or by municipalities. For example, 26 private companies in the Vallejo
Vallejo
Vallejo is a common Spanish lastname. There are various places in the Spanish provinces of Burgos, León, and Cantabria named Vallejo. The name seems to have been rooted as a diminutive of valle...
area initiated a reuse program in 1989 by establishing a for-profit firm, Aguas Industriales de Vallejo. The firm rehabilitated an old municipal wastewater treatment plant and distributes reclaimed water to its shareholder companies at three-quarters of the cost of government supplied potable water.
Pilot project for potable reuse. The Federal District constructed two pilot treatment plants in 1983 to study the potential for the advanced wastewater treatment of secondary effluent for potable reuse, and to examine the potential for treating contaminated ground water. Based upon results of the experimental treatment plants, a new treatment facility was constructed, with a capacity of 0.3 m3/s, and designed for both ground water treatment and direct potable reuse. The established goal of the reuse project was to blend the reclaimed wastewater with treated ground water and add it directly into the distribution system Currently, the reclaimed wastewater is being used for non-potable purposes.
Artificial ground water recharge
Artificial ground water recharge is being practiced in Greater Mexico City using both flood water and treated wastewater.Floodwater. Artificial floodwater recharge has been practiced in the region since 1943, as a method to alleviate flooding rather than as a method to recharge groundwater. Early projects involved runoff retention and surface spreading, channel modification, and infiltration wells. Many of these projects were done in the highly permeable basalt of the upland areas and achieved very high rates of infiltration during periods of heavy rains. Artificial recharge of floodwater using injection wells was first developed in the Federal District around 1953. However, half of the wells were subsequently closed due to operational problems. In 1970, a series of approximately 56 wells was developed for the purposes of disposing of stormwater. These wells were capable of handling up to 35 m3/s of water collectively. Although the wells were not designed for recharge purposes, the storm water possibly reached the aquifer.
Treated wastewater. The Texcoco Project mentioned above has carried out studies on indirect potable reuse of reclaimed wastewater through artificial recharge of the aquifer using secondary and advanced treatment of municipal wastewater. The final effluent may be used in either infiltration ponds or injection wells. In a separate program carried out by the Federal District, a pilot plant injected advanced treated water directly into the aquifer at a rate of up to 0.05 m3/s. Monitoring wells were used to gauge changes in water quality and pressure levels.
Water challenges
These include groundwater overexploitationOverexploitation
Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Sustained overexploitation can lead to the destruction of the resource...
, land subsidence
Groundwater-related subsidence
Groundwater-related subsidence is the subsidence of land resulting from groundwater extraction, and a major problem in the developing world as major metropolises swell without adequate regulation and enforcement, as well as a being a common problem in the developed world...
, the risk of major flooding, the impacts of increasing urbanization, poor water quality and intermittent supply, inefficient water use, a low share of wastewater treatment
Wastewater Treatment
Wastewater treatment may refer to:* Sewage treatment* Industrial wastewater treatment...
, health concerns about the reuse of wastewater for irrigation, and limited cost recovery for water. Infrastructure coverage in terms of access to a piped water connection or to sanitation, which is used to monitor the Millennium Development Goals for water supply and sanitation, is almost universal in Greater Mexico City and as such does not constitute a challenge.
Groundwater overexploitation
The Greater Mexico CityGreater Mexico City
Greater Mexico City refers to the conurbation around Mexico City, officially called Mexico City Metropolitan Area , constituted by the Federal District—itself composed of 16 boroughs—and 41 adjacent municipalities of the states of Mexico and Hidalgo...
's exponential population growth has depleted its groundwater resources. Recharge of the aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
is about 31.6 m3/s compared to abstraction of 59.5 m3/s, resulting in an overdraft of about 28 m3/s. In 1983, systematic monitoring of the water levels in the aquifer began. Since that time, the average annual declines in ground water levels range from 0.1 to 1.5 meters per year in different zones. At the current rate of depletion, it has been calculated that the estimated volume of storage corresponds to between 200 and 350 times the annual abstraction. However, a simplistic water balance approach does not account for other realities. For example, the aquifer is vulnerable to geologically-induced water quality problems with increasing aquifer depth and consolidation and fracturing of clay layers. Furthermore, the actual volume available in the main aquifer would likely be less than estimated because of probable decreasing porosity with increasing depth. Also, there are practical, economic limits to the depth of pumping.
The water balance of Greater Mexico is as follows:
| Water sources | |
|---|---|
| Groundwater | 59.5 m3/s |
| Import from Lerma basin | 4.8 m3/s |
| Import Cutzamala system | 14.9 m3/s |
| Rivers and springs | 2.7 m3/s |
| Total | 81.9 m3/s |
| Water use | |
|---|---|
| Municipal use | 64.7 m3/s |
| Industrial use | 4.6 m3/s |
| Agricultural use | 12.6 m3/s |
| Total | 81.9 m3/s |
Land subsidence
The city rests on the heavily-saturated clay of the former Lake Texoco. This soft base is collapsing due to the over-extraction of groundwater. Land subsidence in Mexico City caused by groundwater overexploitation during the last hundred years has been up to 9 meters, resulting in damages to buildings, streets, sidewalks, sewers, storm water drains and other infrastructure.Flooding
Flooding is common in Mexico City, swamping highways and sidewalks. In low-lying neighborhoods such as IztapalapaIztapalapa
Iztapalapa is one of the Federal District of Mexico City’s 16 boroughs, located on the east side of the entity. The borough is named after and centered on the formerly independent municipality of Iztapalapa, which is officially called Iztapalapa de Cuitláhuac for disambiguation purposes...
, residents are so accustomed to seeing a fetid sea of sewage rise in the streets that they have built miniature dikes in front of their homes. Flooding is caused both by the sinking together and increased soil impermeability due to urbanization. If the Emisor Central should fail during the rainy season, modelling shows that a major flood would occur that would inundate the historic center, the Mexico City International Airport
Mexico City International Airport
Benito Juárez International Airport , in Venustiano Carranza, one of the sixteen boroughs into which Mexico's Federal District is divided, is a commercial airport that serves Mexico City, the capital of Mexico...
and the eastern boroughs of Mexico City.
Increasing urbanization
Urban growth reduces the permeability of the soil in groundwater recharge areas and increases the risk of flooding. It is estimated that the metropolitan area grows annually by 200 to 300 hectares on recharge areas. With every square meter that is built up, on average 170 liters of annual recharge are lost. Thus, for every hectare built up, the water for 500 families are lost and the pressure on groundwater increases further. Between 1989 and 1994 the Federal District declared six Environmental Protection Zones, primarily in forests and mountain slopes, with a total area of almost 5,000 hectares, in order to protect them from urbanization.Water quality and intermittent supply
Water quality. Poor water quality is a concern both at the source and at the point of use. Groundwater below Mexico City was initially believed to be protected from contamination by a thick impervious layer. However, this layer has fractured due to land subsidence. Furthermore, the natural upward flow of water in the artesian aquiferArtesian aquifer
An artesian aquifer is a confined aquifer containing groundwater under positive pressure. This causes the water level in a well to rise to a point where hydrostatic equilibrium has been reached. This type of well is called an artesian well...
has now been reversed due to groundwater depletion. The Groundwater under Mexico City thus is believed to be increasingly vulnerable to contaminants from waste dumps and industrial sites leaching to the aquifer. Furthermore, the deep drainage system penetrates below the clay aquitard in some places into the main aquifer. During periods of heavy rain, wastewater seeps out from the deep tunnels into the surrounding subsoil contaminating the aquifer.
Leaks in the distribution system are a major cause of concern for drinking water quality. When the soil is permeated by sewage from leaking sewers or from other sources, then leaky pipelines will be infiltrated with contaminated water when pressure is low. According to the Federal District's water quality laboratory, neighborhoods that experience more frequent interruptions in service have poorer quality water compared to neighborhoods with a constant supply. The percent of household tap samples in compliance with the residual chlorine standard (0.2 milligrams/liter) ranged from 87 to 100 percent in tests undertaken in 1993 and was notably low among southeastern counties (Iztapalapa
Iztapalapa
Iztapalapa is one of the Federal District of Mexico City’s 16 boroughs, located on the east side of the entity. The borough is named after and centered on the formerly independent municipality of Iztapalapa, which is officially called Iztapalapa de Cuitláhuac for disambiguation purposes...
, Tláhuac
Tláhuac
Tláhuac is one of the 16 delegaciones into which Mexico's Federal District is divided. It is located on the east edge of the district and is largely rural in character. The main town, San Pedro Tláhuac, is situated alongside a lake, and is the site of a 16th century church. The borough had a 2010...
, and Xochimilco
Xochimilco
Xochimilco is one of the sixteen delegaciones or boroughs within Mexican Federal District. The borough is centered on the formerly independent city of Xochimilco, which was established on what was the southern shore of Lake Xochimilco in the pre-Hispanic period...
). Household water storage tanks, or tinácos, are common on almost all household rooftops and are used to store water when water pressure in the system is inadequate. In many instances, the tanks are open and not cleaned regularly, permitting the residual chlorine to dissipate and encouraging the growth of microorganisms. The standard levels of chlorine (0.2 milligrams/liters) maintained in the distribution system as it reaches the customer's tap are not sufficient to inactivate microorganisms that may have entered the pipelines.
Intermittent supply. Water supply in many parts of Greater Mexico City is intermittent and pressure is often insufficient. Users thus have to complement their water supply with water bought from tanker trucks, or pipas. Occasionally, water supply is even cut for several days, as it occurred in January 2009 when the water supply from the Cutzamala system had to be reduced cutting water to 5.5 million people for three days. This incident was followed by a second supply cut in March 2009, and most recently a third cut in April 2009. This third cut was done in response to alarmingly low levels in the city's water reserves, and reparations being undertaken on the Cutzamala system. It lasted 36 hours, and left over five million city residents without water services. In response, the Mexico City government has had to implement an emergency supply response program, providing water in tanker trucks and bottles to residents of the affected communities.
Limited wastewater treatment and concerns about reuse for irrigation
As mentioned above, only 15% of the wastewater in Greater Mexico City currently receives treatment. Storm water, untreated municipal wastewater and partially treated industrial wastewater mix with each other and are reused for irrigation on a large scale.There are concerns about the health and environmental impacts of the reuse of untreated wastewater from Mexico City for irrigation. Crops to be grown using wastewater are restricted to crops not eaten raw, but these restrictions are difficult to enforce and farmers also grow vegetables using wastewater. According to a study by the International Water Management Institute
International Water Management Institute
The International Water Management Institute is a non-profit research organisation with headquarters in Colombo, Sri Lanka, and offices across Africa and Asia...
(IWMI), these risks need to be carefully considered, but the importance of this practice for the livelihoods of countless smallholders must also be taken into account. Studies on soils irrigated with untreated wastewater for 50 years show an accumulation of heavy metals in the soil, but also that they accumulated in plants to a lower extent. Another study found bacterial contamination of canal water used for bathing and of groundwater used for drinking water supply in the irrigated areas where wastewater was being reused, resulting in a high incidence of diarrhea and skin irriations.
Inefficient urban water use
The Federal District had a level of non-revenue waterNon-revenue water
Non revenue water is water that has been produced and is “lost” before it reaches the customer. Losses can be real losses or apparent losses . High levels of NRW are detrimental to the financial viability of water utilities, as well to the quality of water itself...
of 40%, close to the Mexican average, meaning that only 60% of the water pumped into the system is actually being billed for. A large share of non-revenue water is due not to leakage, but to illegal connections. Furthermore, SACM, the water department of the District, has by far the lowest collection efficiency among the 25 major municipalities, with only 40% of all bills being paid. Thus only 24% (60% is being billed, 40% of the bills being paid) of the water pumped into the system is being paid for. The level of non-revenue water in Mexico State is lower, so that the average level in the metropolitan area is 36%.
Per capita water use figures are difficult to compare over time, because sources typically do not indicate if water losses are included in the figures or not. The National Statistical Institute gives water use in the Federal District at 223 liter/day in 1999 (probably after losses), including 164 liter of residential use and 59 liter for industrial and commercial uses. This is only about one third of average water use in the United States
Water supply and sanitation in the United States
Issues that affect water supply and sanitation in the United States include water scarcity, pollution, a backlog of investment, concerns about the affordability of water for the poorest, and a rapidly retiring workforce...
, which is 603 liter/capita/day. However, it is still one third higher than water use in France
Water supply and sanitation in France
Water supply and sanitation in France is universal and of good quality. Salient features of the sector compared to other developed countries are the high degree of private sector participation using concession and lease contracts and the existence of basin agencies that levy fees on utilities in...
, which is only 165 liter/capita/day. Another source gives average per capita water use in 1994 as 364 and 230 liters per day for the Federal District and Mexico State respectively (probably before losses). Authorities attribute the larger per capita use in the Federal District to the fact that the Federal District is more developed and includes more commercial and industrial activity than the State of Mexico. However, lower tariffs and lower metering in the Federal District may also influence the higher water use.
Limited cost recovery
There is a major gap between the cost of supplying water, a quarter of which is imported through expensive interbasin transferInterbasin transfer
Interbasin transfer or transbasin diversion are terms used to describe man-made conveyance schemes which move water from one river basin where it is available, to another basin where water is less available or could be utilized better for human development...
s from the Lerma
Lerma River
The Lerma Santiago River is Mexico's second longest river. It is a river in west-central Mexico that begins in Mexican Plateau at an altitude over above sea level, and ends where it empties into Lake Chapala, Mexico's largest lake, near Guadalajara, Jalisco...
and Balsas
Balsas River
The Balsas River is a major river of south-central Mexico. The basin flows through the states of Puebla, Morelos, Guerrero, and Mexico. The river empties into the Pacific Ocean at Mangrove Point, adjacent to the city of Lázaro Cárdenas, Michoacán...
basins, and what is recovered from users. Reasons for low cost recovery include illegal water connections, low tariffs and poor bill collection, in particular in the Federal District
Mexico City
Mexico City is the Federal District , capital of Mexico and seat of the federal powers of the Mexican Union. It is a federal entity within Mexico which is not part of any one of the 31 Mexican states but belongs to the federation as a whole...
.
Cost recovery in Mexico State is much higher than in the Federal District. For example, the city of Toluca
Toluca
Toluca, formally known as Toluca de Lerdo, is the state capital of Mexico State as well as the seat of the Municipality of Toluca. It is the center of a rapidly growing urban area, now the fifth largest in Mexico. It is located west-southwest of Mexico City and only about 40 minutes by car to the...
in Mexico State charges residential users 9.5 pesos (US$0.72)/m3 for a consumption of 30m3, including a sanitation surcharge, the sixth-highest among the country’s 25 major municipalities. This still falls short of the cost of bulk water from the Cutzamala system at nearly 10 pesos (US$0.78)/m3, without taking into account the cost of distributing water and of sanitation.
In 2004 the Federal District charged residential users 3.3 pesos (US$0.26)/m3 for the same consumption without any surcharge for sanitation, the fourth-lowest among the same municipalities. The remainder is effectively subsidized by the municipal and federal governments. In August 2007 a conflict had erupted between Conagua and the Federal District when Conagua increased the tariff for water supplied through the Cutzamala system and the District refused to accept the increase.
Social impact of water crisis
The human rights commission of the District (CDHDF) warned in summer 2009 that water shortage could cause a "spiral of violence" and that low-income families are paying more for water of lower quality and only receive it at certain hours of the day. This situation causes "social unrest". In early August 2009, the head of Conagua, José Luis Luege, had announced an "imminent and indefinite increase in water rationing in the Mexico valley and federal district." Because water from Cutzamala and Lerma systems, supplying together one quarter of the metropolitan area's water, enters the city from the Northwest where wealthier neighborhoods predominate, water supply tends to be more continuous than in the Southeast of the city where most of the poor live.Response to challenges
In response to these challenges, two major programs are underway. The National Water Commission has launched a massive US$2.8 billion Water Sustainability Program in 2007 for bulk water supply, drainage and wastewater treatment for the period 2007-2012. In parallel, the government of the Federal District has launched a 15-year Green PlanGreen Plan
Green Plans are comprehensive management plans that have the final goal of achieving environmental and economic sustainability. They are integrated, all-inclusive strategies that replace traditional single-issue policies. Green Plans have been implemented in several regions of the world including...
that also includes drainage and wastewater treatment. In addition it emphasizes water conservation and water reuse through aquifer recharge. Both plans aim at reducing non-revenue water
Non-revenue water
Non revenue water is water that has been produced and is “lost” before it reaches the customer. Losses can be real losses or apparent losses . High levels of NRW are detrimental to the financial viability of water utilities, as well to the quality of water itself...
.
Water Sustainability Program
In November 2007, President Felipe CalderónFelipe Calderón
Felipe de Jesús Calderón Hinojosa is the current President of Mexico. He assumed office on December 1, 2006, and was elected for a single six-year term through 2012...
launched a US$2.8 billion Water Sustainability Program for the Valley of Mexico through 2012. The program amplifies the earlier Program for the Sanitation of the Valley of Mexico. Its objectives are to avoid major floods such as the 2007 Tabasco flood
2007 Tabasco flood
The 2007 Tabasco flood occurred in late October and early November 2007 in the Mexican states of Tabasco and Chiapas, in which as much as 80% of the former was left under water. At least 20,000 people were forced to seek emergency shelter...
, to treat all the wastewater collected, and to reduce groundwater overexploitation.
Water supply and exchange. 14 m3/s more water would be mobilized from various sources. The largest of these imports (5 m3/s) will consist of groundwater from the Tula Valley North of Greater Mexico, where the groundwater table has increased from many years of irrigation with untreated wastewater, at a cost of US$255 million. The second-largest source of additional water will be mobilized through an exchange of treated wastewater for clean water at present used for irrigation in the Vaso del Christo area (4m3/s), at a cost of 140 million. As part of the "rehabilitation" of existing sources, the Cutzamala system is expected to be expanded by 3 m3/s, at a cost of US$275 million. Finally, 2 m3/s would be made available from the Guadelupe dam in Mexico state at a cost of US$40 million.
Storm water drainage and wastewater treatment. The program foresees the construction of the Emisor Oriente in parallel to the Emisor Central. In February 2009, Conagua oversaw the purchase of the first of three underground drills from German firm Herrenknecht. The new drill will be used to begin excavations for the tunnel in April 2009. All works on the tunnel system are expected to be completed in September 2012, at an expected cost of MXP 13 billion (approx. USD 1 billion).
Out of the discharge of the Emisor Oriental 23 m3/s would be treated in a planned wastewater treatment plant in El Salto
El Salto
El Salto is a climbing area in the Mexican state of Nuevo León. It lies in the Ciénega de González, about two hours from Monterrey. It is the only climbing area in northern Mexico where overhanging limestone full of tufa can be found...
in Hidalgo State to deliver water to the Tula Irrigation District. Almost half of the investment (US$1.28 bn) will be for the construction of 6 wastewater treatment plants, the largest of which by far would be the Atotonilco (El Salto) plant. The US$900m contract to finance, build and operate the plant, allegedly the largest wastewater treatment plant in the world with a maximum capacity of 4.3 million cubic meter/day, was awarded in 2011 to a consortium led by the Spanish company Acciona.
The achievement of the program objective to both supply a growing population with water and to reduce pressure on the aquifer rests on the assumption that leakage will be reduced from 36% in 2005 to 25% in 2030.
Financing. The program is being financed from the following sources:
- Private sector:The wastewater treatment plants are expected to be financed by the private sector through equity and debt under Build-Operate-TransferBuild-Operate-TransferBuild-own-operate-transfer or build-operate-transfer is a form of project financing, wherein a private entity receives a concession from the private or public sector to finance, design, construct, and operate a facility stated in the concession contract...
(BOT) projects - Federal government: The federal government directly finances some of the works, executed by Conagua
- The Trust Fund No. 1928, created by the Federal District, the State of Mexico and the Federal Government, will finance part of the works. The Trust Fund is replenished by the payments made by the Federal District and the State of Mexico for bulk water supplied to them by Conagua. It is administered financially by the public infrastructure Bank BanobrasBanobrasBanco Nacional de Obras y Servicios Públicos, SNC or Banobras is state owned development bank in Mexico. Its core business is sub national and project finance...
, with Conagua acting as technical coordinator. The Trust Fund was modified in November 2008 to allow the financing of a broader range of projects. - A Metropolitan Fund, or National Infrastructure Fund, established at the national level for infrastructure investments, also finances some works
- Loans from the state-owned investment bank Banobras.
Green Plan
Green Plan
Green Plans are comprehensive management plans that have the final goal of achieving environmental and economic sustainability. They are integrated, all-inclusive strategies that replace traditional single-issue policies. Green Plans have been implemented in several regions of the world including...
(Plan Verde) that aims at the sustainable development of the District along seven major axes, one of which is water. In 2008 it had a budget of US$6 million. Concerning water, it foresees reaching an equilibrium in the aquifer, reducing residential water use, reducing network losses, increasing the reuse and the treatment of wastewater, and the creation of parks around the lakes Tláhuac
Tláhuac
Tláhuac is one of the 16 delegaciones into which Mexico's Federal District is divided. It is located on the east edge of the district and is largely rural in character. The main town, San Pedro Tláhuac, is situated alongside a lake, and is the site of a 16th century church. The borough had a 2010...
and Xochimilco
Xochimilco
Xochimilco is one of the sixteen delegaciones or boroughs within Mexican Federal District. The borough is centered on the formerly independent city of Xochimilco, which was established on what was the southern shore of Lake Xochimilco in the pre-Hispanic period...
. More specifically, it foresees increased aquifer recharge through changes in land use and recharge wells; the metering
Water metering
Water metering is the process of measuring water use through water meters.- Prevalence :Water metering is common for residential and commercial drinking water supply in many countries, as well as for industrial self-supply with water. However, it is less common in irrigated agriculture, which is...
of all users by 2010 and making all users pay for water; identify and regularize illegal connections; the construction of tertiary wastewater treatment plants for the injection of treated wastewater into the aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
. The Plan is expected to relieve pressure on the aquifer by 6.8 m3/s, including 3.3 m3/s by reducing leakage, 1 m3/s through water conservation and 2.5 m3/s by recharging groundwater with treated wastewater. These measures together, if successful, would reduce groundwater abstraction in Greater Mexico by 10% and the overdraft by 25%, and thus still fall short from establishing an equilibrium between abstraction and recharge.
Enhanced private sector participation in the Federal District from 2010 onwards
In mid-2009 the finance chief of the Federal District, Mario Delgado, and the director general of the District's water company SACM announced that from mid-2010 onwards the District intends to enhance the participation of the private sector in water supply through concessions, under which the concessionnaires would buy bulk water and distribute it, thus providing an incentive to reduce non-revenue waterNon-revenue water
Non revenue water is water that has been produced and is “lost” before it reaches the customer. Losses can be real losses or apparent losses . High levels of NRW are detrimental to the financial viability of water utilities, as well to the quality of water itself...
. A total of four concession covering 11 of the District's 16 delegaciones would be bid out. The concessions would replace the existing four service contracts for metering and billing.
Past responses to challenges
Past responses to the water challenges facing Greater Mexico City included an ambitious water conservation campaign initiated in 1989, as well as an increase in metering and a reduction in leakage through private sector participation begun in the early 1990s.Water conservation program in the 1990s
In 1989, in parallel with the introduction of stricter national water efficiency standards for household appliances, Mexico City launched an ambitious program to replace conventional toilets (using 16 liters) with 6-liter models, replacing 350,000 toilets by 1991. The program also included a large-scale public information campaign and an increase in water tariffs. The impact of the program is difficult to assess, since available figures on water consumption are difficult to compare over the years, because it is not clear whether they include water losses or not and whether they refer only to residential consumption or total consumption.Private sector participation in the Federal District since 1993
Manuel Camacho SolísManuel Camacho Solís
Manuel Camacho Solís is a Mexican politician who served in the cabinets of presidents Miguel de la Madrid and Carlos Salinas...
, the Head of Government of the Federal District
Head of Government of the Federal District
The Head of Government wields executive power in the Mexican Federal District.The Head of Government serves a six-year term, running concurrently with that of the President of the Republic....
from 1988 to 1997 who was appointed by President Carlos Salinas
Carlos Salinas
Carlos Salinas de Gortari is a Mexican economist and politician affiliated to the Institutional Revolutionary Party who served as President of Mexico from 1988 to 1994. Earlier in his career he worked in the Budget Secretariat all the way up to Secretary...
(PRI), led the process of private sector participation in water supply in Mexico City in the early 1990s. At that time water revenues were extremely low, there was no functioning customer database, virtually no metering, and low bill collection efficiency. At least 22% of customers did not receive bills at all, partly because water connections were carried out by one department and billing by another which did not receive any information about water connections from the former.
In November 1992 bids were launched, in March 1993 the results were announced and in November 10-year service contracts were signed with four firms, each for one block of the capital:
- Block 1 with four boroughs in the North was awarded to SAPSA (Servicios de Agua Potable S.A.), constituted by the large Mexican construction firm Ingenieros Civiles Asociados (ICA), with the Bank Banamex and the French firm Générales Des Eaux (VivendiVivendiVivendi SA is a French international media conglomerate with activities in music, television and film, publishing, telecommunications, the Internet, and video games. It is headquartered in Paris.- History :...
), - Block 2 with three boroughs in the center was awarded to IASA, (Industrias del Agua S.A.), which included businessmen from Monterrey and the British firm Severn TrentSevern TrentSevern Trent plc is a British public utility. It is traded on the London Stock Exchange and is a constituent of the FTSE 100 Index.Severn Trent is a group of companies employing more than 15,000 people across the UK, US and mainland Europe, with some involvement in the Middle East.The main...
- Block 3 with the impoverished Southeast was attributed to TECSA (Tecnología y Servicios de Agua S.A.), which included Bancomer, Bufete Industrial, and the French firm Lyonnaise Des Eaux-Dumex (SUEZSUEZSuez S.A. was a leading French-based multinational corporation headquartered in the 8th arrondissement of Paris, with operations primarily in water, electricity and natural gas supply, and waste management. Suez was result of a 1997 merger between the Compagnie de Suez and Lyonnaise des Eaux, a...
-Ondeo Services) as well as the British firm Anglian WaterAnglian WaterAnglian Water is a privatised water company that operates in the East of England. Named for East Anglia, apart from Norfolk, Suffolk and Cambridgeshire it also covers Lincolnshire, Essex, Bedfordshire, Buckinghamshire, Northamptonshire, a small part of north Nottinghamshire and Greater London...
. - Block 4 with five wealthy delegations in the Southwest was awarded to AMSA (Agua de México S.A.), which included the GUTSA group and the British firm North West Water International.
The process of private sector participation foresaw three phases:
- First phase (1994–1995): Updating of the user registry.
- Second phase (1995–1998): Meter reading, billing, and some aspects of collection.
- Third phase (1998–2003): Leak detection and repair, extension and rehabilitation of the secondary distribution network.
The city remained in charge of the water production, treatment and main distribution infrastructure, as well as some aspects of collection and the sanitation infrastructure. It also set water tarirfs. The first two phases were successful. Under the contracts the number of metered connections increased from virtually none in 1994 to up to 1,264,500 in 2002, reaching more than 90% of all users. The third phase, however, was less successful.
Between 1994 and 1998 the amount billed increased by almost 30% in real terms. But the amount collected stagnated, since private operators were not in charge of bill collection. Collection efficiency actually declined from 84% to 69% The service itself remained unchanged in terms of intermittency of supply and water quality, since these aspects were not part of the contracts. Tariffs and cost recovery also remained unchanged, with revenues covering less than 75% of operating costs. The third phase of turning over increased responsibility to the private sector was abandoned after the PRD won elections in 1997 and renegotiated the contracts.
The PRD mayor Andrés Manuel López Obrador
Andrés Manuel López Obrador
Andrés Manuel López Obrador , also known as AMLO or El Peje, is a Mexican politician who held the position of Head of Government of the Federal District from 2000 to 2005, before resigning in July 2005 to contend the 2006 presidential election, representing the unsuccessful Coalition for the Good...
(2000–2005) renewed the contracts in 2004 for another five years,. His successor Alejandro Encinas Rodríguez
Alejandro Encinas Rodríguez
Alejandro Encinas Rodríguez is a left-wing Mexican politician affiliated with the Party of the Democratic Revolution. He served as the 4th Head of Government of the Federal District from 2005 to 2006....
initially announced that the District would terminate the contracts even before they expired, but his successor Marcelo Ebrard
Marcelo Ebrard
Marcelo Luis Ebrard Casaubón is the current Head of Government of the Federal District since December 5, 2006. He is a Mexican politician affiliated to the Party of the Democratic Revolution who served as Secretary-General of the former Mexican Federal District Department, minister of public...
actually extended them for another year until mid-2010.
Valley of Mexico Sanitation Project
In 1996 the Inter-American Development BankInter-American Development Bank
The Inter-American Development Bank is the largest source of development financing for Latin America and the Caribbean...
(IDB) approved a US$365 million loan for the Valley of Mexico Sanitation Project, in parallel with a loan of US$410 million by the Overseas Economic Cooperation Fund
Overseas Economic Cooperation Fund
The term Overseas Economic Cooperation Fund can refer to:*the Economic Cooperation Organization , which was funded in 1985 by Iran, Pakistan and Turkey to improve socio-economic development....
of Japan. The IDB project, which closed in 2005, foresaw the construction of 4 wastewater treatment plants with a total capacity of 74.5 m3/s as well as the rehabilitation of drainage systems.
Further reading
Cecilia Tortajada: Water Management in Mexico City Metropolitan Area, in: International Journal of Water Resources Development, Vol. 22, No. 2, p. 353-376, June 2006, Third World Centre for Water Management, Mexico.See also
- Drainage of the Valley of Mexico
- Water supply and sanitation in MexicoWater supply and sanitation in MexicoWater supply and sanitation in Mexico is characterized by achievements and challenges. Among the achievements is a significant increase in access to piped water supply in urban areas as well as in rural areas between 1990 and 2006; a strong nationwide increase in access to improved sanitation ...
- Water resources management in MexicoWater resources management in MexicoWater resources management is one of Mexico's pressing concerns, and it is imposing heavy costs to the economy. The arid northwest and central regions contain 77% of Mexico's population and generate 87% of the gross domestic product . Poor southern regions have abundant water resources...
- Politics of MexicoPolitics of MexicoThe politics of Mexico take place in a framework of a federal presidential representative democratic republic whose government is based on a congressional system, whereby the president of Mexico is both head of state and head of government, and of a multi-party system...
External links
- National Water Commission (Spanish)
- Mexico City government (Spanish)
- Water utility of the Federal District (SACM) (Spanish)
- Mexico State:Ministry of Water and Public Works-State Water Commission (Spanish)
- UNESCOUNESCOThe United Nations Educational, Scientific and Cultural Organization is a specialized agency of the United Nations...
: World Water Assessment Program - Case Study:Sustainable urban water management in the State of Mexico, 2006