The Urban Water Cycle: Mexico City as an example

Blanca Jiménez

http://maps.grida.no/go/graphic/urban_water_cycle

Mexico City

• Tenochtitlan was founded by the Aztecs in 1325 dC

• In a SAFE Place and plenty with water

• BUT that meant that the Mexico Valley was an endorreic basin at 2,240 masl

Water Cycle in the Mexico City Valley

The Spanish arrived, in 1519 d.C.

Tenochtitlan was a “Megacity”–200,000 inhab.–Four streets (dikes)

communicated it with land and separated 5 lakes

The Spanish people–Did not understand the

functioning and destroyed dikes

–Rivers were used as sewers Since then both lack of

water and floods are the main urban water problems Tenochtitlan was the most

important city and was an island

Mexico City in 2010 21,000,000 million people Metropolitan area = the

Federal District (Tenochtitlan) + 37 adjoining municipalities

Water is managed independently in the 38 entities

In total, 85.7 m3/s (7.4 MILLIONS m3/d) 48% through the network

44% directly pumped by the water works utilities, farmers and industries from the local water

8%, reused treated wastewater

WATER SUPPLY AND USE

7% from the Lerma (100 km far and 300 m above the Mexico City level )

19% from the Cutzamala river (130 km away and 1,100 m)

3.4 times the Eiffel Tour

Height

First use water (78 m3/s) comes from :

73% from 1,965 wells located within the City

1% from local rivers

Water Uses74% municipal and industries

branched to the city network16% irrigation (40,000 ha on

the Valley)2% self supplied industries 8% non drinking water reuse

Water supply service 89% coverage , i.e., 2.3 million people receive water through water tanks

They pay 10 times the network water price

The rest, receive water through the network

BUT they receive it intermittentlyPoor qualityAs consequence each house has their “own storage (TINACOS) and pumping systems and potabilize water

Water sources quality Local groundwater quality is increasingly deteriorating

Due to overexploitation, uncontrolled non source point pollution, and industrial and municipal discharges

-

Parameter , mg/L Original Present value Dissolved Solids 1,000 20,000Sodium 50-100 600-800 Ammonical nitrogen

0-0.03 6-7

Iron < 0.1 3-7

In groundwater:

In the western part (uncontrolled dumping sites used to exist)

High content of a wide variety of organic compounds (even vitamin B)

- In the southwest High Fe and Mn content

- In the South (no sewer and 500,000 septic tanks discharging sewage to a volcanic soil

Nitrates, ammoniacal nitrogen and fecal coliforms

Water quality and drinking water sources

To potabilize water Chlorination for groundwater sources and Alum

coagulation, sedimentation and chlorination for surface water

Processes selected based on characteristics measured 30-40 years ago, i.e., pollutants of concern are not remove

In chlorinated water THM (Trihalomethanes, carcinogenic) 84 microorganisms of 9 genera associated with

human fecal pollution (Streptococcus, Helicobacter pylori -associated gastric ulcers and cancer and coliphages MS-2, before and even in some cases after chlorination - resistance to chlorine?)

To have potable water Each user

Boils, apply chemical disinfectants (chlorine, iodine or silver), uses small potabilization systems (filtration with ozone or UV-light disinfection)

Potabilization cost varies between 4-10 USD/m3}

Or buys bottled water Mexico is the 2nd consumer of

bottled water Bottled water is 240 to 10,000

more expensive than tap water

Cost represents for a family of 4 persons living on minimum wage 11-21% of its income

 IMPACTS DUE TO THE EXCESIVE WATER

DEMAND

1. Overexploitation of the local aquifer

at a 117% rate  As a result there is

soil subsidence sinking rates in

some places up to 40 cm/year

In 1954 the problem was perceived but center had already sunk 7 m

19101980

2. Soil subsidence is creating   Loss of the sewage/drainage

capacity (no slope or inverted slope)

20-30 floods per year > 30 cm in height with wastewater

To recover capacity 305 million USD are being invested

Difficulties to maintain the Deep Drainage as it conveys all year round wastewater

If it fails, 400 km2 of the City center will be flooded with 1.2 m of wastewater affecting at least 4 million people.

2. Soil subsidence is creating:

Structural problems in buildingsFor Mexico City Cathedral

Differential soil sinking has led to an 87 cm difference between the apse and the western bell tower in 50 years

To redress it $ 32.5 million USD were invested in 2000

The metro (metropolitan train) rails need to be leveled each year

2. Soil subsidence is creating

Leaks in water and wastewater networks.

40% of the water supplied is lost, amount enough to supply 3,200,000 million people with 300 L/capita (the actual supply is 153 L/d )

Sewage leaks Have not been evaluated

3. Due to the Water transfer from other basins

At the Lerma region which used to be a lake,

fishing disappeared and people had to live off the land.

The Chapala Lake fed by the Lerma system has experienced a level decrease of 5 m.

Cutzamala region Reduction of the amount of

water available for power generation and local population

Women mazahuas movement

ATMOSPHERIC DEPOSITION

• In 1998 the regular presence of gasoline and oil-derived compounds in Mexico City’s wastewater was reported. It may come from Air pollution (3 million automobiles that

“discharge” (evaporation) 82,000 tons/yr Oil pipelines leaks solvents used as cleaning products (77,000

tons/yr)

evaporation and leaks of unburned oil (27,000 tons/yr) domestic gas leaks dry cleaning serviceschemical industry graphical arts.

Air pollution• The average concentration of HC in

Mexico City’s air is 8.8 ppm (2 ppm in Los Angeles in the 1980s), among the compounds reported there are– Toluene, benzene and

formaldehydes– formic acid (2-24 μg/m3)– acetic acid (0.5-7 µg/m3) – propionic acid (0-18 μg/m3)– close to 200 volatile organic

compounds with at least 2-13 carbons have been identified

– alkenes (52-60%)– aromatic compounds (14-19%)– olefins (9-11%) – oxygenated compounds (1-2%) – MTBE

Automobiles also produce• 19,889 tons of < 10 micron particles, • 22,466 tons of SO2

• 1,768,836 tons of CO• 205,885 tons of NOx • 465,021 tons of hydrocarbons

SOLID WASTES FROM SEWERS• Mexico City sewer system is VERY

BIG and COMPLEX

The Sewer system is cleaned each year

2.8 million cubic meters of sludge/solids wastes are produced

Wastes go to the ONLY municipal landfill that is already overloaded

Sediments contain 3-7 log faecal coliforms MPN/g TS2-7 log Salmonella MPN/g TS 4-21viable helminth ova /g TS 89-7955 total petroleum hydrocarbons (mg/kg TS) heavy metalorganic matter, nitrogen and phosphorus

Similar problems in Sao Paulo and Taiwan have been reported

Sewerage system, History 3 artificial exits built to drain

waste and pluvial water In total, Mexico City produces

67.7 m3/s of wastewater 11% is treated and reused

since 1956 The rest, (60 m3/s, mean

conditions but varying from 52 to > 300 m3/s) IS non TREATED AND ALSO RESUED since 1896 for irrigation of the Tula Valley

100% OF WASTEWATER REUSE

Reuse is for • 54% refill

recreational lakes, • 31% green areas

irrigation (6,500ha), • 5% car washing

and fountains • Environmental

restoration, • 8% industrial uses

(Cooling)

The Tula Valley, DescriptionSemiarid area

Pluvial precipitation: 525 mm (5 months per year)

evaporation rate: 1,750 mmOriginal vegetation: Xerophila

scrubs, such as mezquite, sweet acacia, yucca and a wide variety of cacti

1930-40s the Government was thinking on moving people, there was NO water for development

The biggest WW irrigated district in the world

From s 14,000 ha inn 1926 it reached of 90,000 ha in four irrigation districts

Among the most productive ones¡¡¡

Crop Yield, tons/ha Increase%Wastewater ‘First use’

waterCorn 5.0 2.0 150Barley 4.0 2.0 100Tomato 35.0 18.0 94Forage oats

22.0 12.0 83

Alfalfa 120.0 70.0 71Chili 12.0 7.0 70Wheat 3.0 1.8 67

Health effects

Data used by WHO (1989 and 2006) to establish the criteria to reuse wastewater for agricultural irrigation

To be controlled with a WWTP (under construction)

Cifuentes et al., 1992

Parasites Ages Morbidity rates

Raw wastewater

Natural water

Ratio

Ascaris lumbricoides (Helminth)

0 to 45 to 14

> 15

15.316.15.3

2.71.00.5

5.716.011.0

Giardia lamblia (Protozoa) 0 to 45 to 14

> 15

13.69.62.3

13.59.22.5

1.01.01.0

Entamoeba histolytica(Protozoa)

0 to 45 to 14

< 15

7.016.416.0

7.312.013.8

1.01.31.2

Secondary effect Discovered in 1995 At least 25 m3/s of wastewater used to irrigate were infiltrated to the

local aquifer (13 times the natural recharge) Due to wastewater transportation in hundreds of unlined channels, storage in unlined dams, high irrigation rates (1.5-2.2 m/ha.yr) to wash out salts

 As a result the Tula River flow (partially fed from the aquifer) increased from

1.6 m3/s to more than 12.7 m3/s between 1945 and 1995 the water table rose from 50 m below the ground level in 1940 to

form artesian wells with flows varying from 40 to 600 L/s in 1964  The new water sources Are used to supply 500,000 inhabitants after only chlorination

Tula Valley without Tula Valley without wastewater for irrigationwastewater for irrigation

Tula with a “wastewater

river” for irrigation

Groundwater and drinking water quality

In 1938, a change in the water quality of wells began to be noticed

In 1995 it was officially acknowledged that infiltrated wastewater was

the origin of the new water sources

It was the as supply for 500,000 inhab

Several studies to assess the water quality begun

Results No main problems Water was light saline In wells built with no care some microbiological

problem Why not using it for Mexico City supply?

Future water demand

Option to supply this demand Transferring water from other basins and/or Aggressive water reuse programs On site wastewater potabilization OR Returning back groundwater from the Mezquital

Valley

Actual deficit 1-2 m3/sContinuous supply + 5 next years demand 5 m3/sOver exploitation and soil subsidence control >15 m3/sA>t least for 2010 25

Cost comparison of different new water source options for Mexico City (Jiménez and Chavez, 2004)

Supplyaltenatives for Valley of Mexico (2240 masl)

SOURCESOURCE CapacityCapacity

mm33/s/sHeadHead

mmDistanceDistance

kmkmCost Cost

(US$/(US$/mm33))

TemascaltepecTemascaltepec 5.05.0 15701570 8080 0.580.58

AmacuzacAmacuzac 13.513.5 17001700 100100 0.860.86

TecolutlaTecolutla 9.89.8 12661266 116116 0.850.85

Mezquital ValleyMezquital Valley 10 10 400400 7070 0.250.25

Mexico City Mexico City (Reuse)(Reuse)

>10>10 00 00 1.51.5

Atmospheric deposition•Air pollutants by direct deposition or settling are transfer to and water.

AIR POLLUTION CONTROL

Dumping sites, municipal landfills and hazardous waste confinement sites

Especially old landfills (<1970’s)

Emerging pollutants sources SURVEILLANCE, TRACKING AND

CONTROL

and solid products wastes–Infiltration wells as wastewater disposal option

BETTER SURVEILLANCE OF THE WASTES MANAGEMENT IN INDUSTRIES; CLEANER> PRODUC TION CONCEP AND SOCIAL

ENVIRONMENTAL RESPONSIBILITY APPRAOCH

Subsurface storage tanks ( gasoline, oil or chemical compounds) leak

Especially if they are > 20 years oldMONITORING AND MAINTENANCE

PROGRAM

Sewers: Infiltration As high as 500 mm/yr in highly

populated urban areas SEWERS MAINTENANCE

Leaks in the water network From 8-60%

MAINTENANCE OF URBANINFRASTRUCTURE

Storage or treatment Tanks/Ponds (containing wastewater, industrial liquid wastes , or

stormwater) frequently leak •Even if waterproofed, infiltration occurs (10-20

mm/d)

MONITOR AND CONTROL OF NON POINT URBAN DISCHARGES TO SOIL AND

GROUNDWATER

Urban Septic tanks Discharge partially treated

wastewater In Sana’a, Yemen

represent 80% of the urban recharge

NEW SOLUTIONS FOR ON SITE TREATMENT

Transportation of polluted water in open channels or rivers

- Specially in poor periruban areas

Infiltrate or discharge into water Industrial non point sources

discharges•Handling of liquid courses

DICHARGING AND TRANSPORTING DO NOT GET

RID OF POLLUTION

Treated wastewater disposal

During the dry season 70% of the water supply in the Tamesis river

(England) comes from WWTP effluents

THE WAY IN WHICH WTP ARE CONCEIVE NEED TO CHANGE TO

CLOSE THE WATER LOOP

Excessive water demand in a limited area

-Water efficient Use- Water Reuse

- Urban Growiing balnace with the local water availability

Non intentional Reuse of treated and non treated wastewater

Reintegrating used water concept rather than disposal

concept

CONCLUSIONS• Mexico City is one example, but there are many other

(similar or parts, developedn and developing)• Cities need water (in appropriate quantity and quality)• They modify the water cycle in many ways• Impacts often are overlooked putting at risk cities and

the “urban water” sustainability• To control such impacts

– causes need first to be acknowledge and identified– appropriate and affordable measures should be put in place

• For both the hydrological urban water cycle concept is useful and to study it inter/transdiciplinary effort need to be made

Water NetworkIANAS

Dr. José Galizia TundisiDra Blanca E Jiménez Cisneros

IANAS Water Programme

• (a) establish National Water Committees that will help Academies provide advice to governments and society, thus enhancing their social relevance;

• (b) prepare white papers providing a strategic view on national water resources;

• (c) implement capacity building activities; • (d) discuss new perspectives and innovative solutions

for water management; • (e) set the stage for the future publicizing and

implementation of the recommendations of the IAC Study Panel on Water.

Meeting in Domingo, 29 February to 01 March 2008

1) Argentina, Raul Lopardo2) Bolivia, Fernando Urquidi3) Venezuela, Ernesto Gonzalez4) Brazil, Jose Galizia Tundisi5) Canada, Keith Hipel6) Cuba, Mercedes Arellano

1) Guatemala, Manuel Basterrechea2) Haiti, Wilson Celestin3) Nicaragua, Katherine Vammen4) Peru Adolfo Toledo and Axel Dourojeani5) Dominican R., Rafael Osiris de Leon6) Trinidad & Tobago, Vincent Cooper7) United States, Henry Vaux

Water in X COUNTRY , Book• Water Resources

• Water and sustainable development• Climate Change and Water• Groundwater/Ecohidrology

• Water Quality• Water and ecosystems

• Limnology• Water and Health

• Water Services for Municipalities• Water, Livestock and Agriculture

• Water and industry• Urban Water

• Water and Ecotourism• Water and Energy

• Water and Transportation• Aquaculture

• Hydroeconomy• Institutional and Legal Framework

• Water and Women • Public Participation

NEXT STEP

COUNTRY TOR Presentation

English Version

Spanish Version

White Paper

Book

Argentina OK In processBolivia, Fernando Urquidi OK In process OKBrazil OK OK In process OKCanada, Keith HIpel OKChile, Niño Yarko OK In process In processColombia, Gabriel Roldán and Claudia Campuzano

OK OK

Costa Rica, Hugo Hidalgo OK OK In processCuba, Mercedes Arellano Acosta OK In process OKGuatemala, Manuel Basterrechea OK OK OKHaiti, Wiston Celestin OKMexico, Blanca Jimenez OK In Process OK In process OKNicaragua, Katherine Vammen OJ In process OK In processPeru, Julio Kuroiwa OK OK In processDominican R., Rafael Osiris de Leon

OK

Trinidad & Tobago, Vicente Cooper

OK

United States, Henry Vaux OK In processVenezuela, Ernesto González OK OK OK

IN SEVERAL CASES THERE ARE > 1 author

NEXT STEP, 5th Meeting in Argentina

• End country profiles• End white paper• Begin of URBAN water

– 60% of World population live in cities

– But, in LA is 70% ¡¡¡¡¡¡

Think Water¡¡¡