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The Urb an Water Cycle: Mexico City as an example Blanca Jiménez

The Urb an Water Cycle: Mexico City as an example Blanca Jiménez. 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.

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The Urb an Water Cycle: Mexico City as an example Blanca Jiménez

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  1. The Urban Water Cycle: Mexico City as an exampleBlanca Jiménez

  2. 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

  3. Water Cycle in the Mexico City Valley

  4. 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

  5. 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

  6. WATER SUPPLY AND USE • First use water (78 m3/s) comes from : • 73% from 1,965 wells located within the City • 1% from local rivers • 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

  7. Water Uses • 74% municipal and industries branched to the city network • 16% irrigation (40,000 ha on the Valley) • 2% self supplied industries • 8% non drinking water reuse

  8. 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 intermittently • Poor quality • As consequence each house has their “own storage (TINACOS) and pumping systems and potabilize water

  9. Water sources quality • Local groundwater quality is increasingly deteriorating • Due to overexploitation, uncontrolled non source point pollution, and industrial and municipal discharges -

  10. Water quality and drinking water sources 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

  11. 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?)

  12. 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

  13. 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 1980 1910

  14. 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

  15. 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.

  16. 2. Soil subsidence is creating: • Structural problems in buildings • For 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

  17. 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

  18. 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

  19. 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 services • chemical industry • graphical arts.

  20. 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

  21. 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

  22. Wastes go to the ONLY municipal landfill that is already overloaded • Sediments contain • 3-7 log faecal coliforms MPN/g TS • 2-7 log Salmonella MPN/g TS • 4-21viable helminth ova /g TS • 89-7955 total petroleum hydrocarbons (mg/kg TS) • heavy metal • organic matter, nitrogen and phosphorus • Similar problems in Sao Paulo and Taiwan have been reported

  23. 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 ANDALSO RESUED since 1896 for irrigation of the Tula Valley • 100% OF WASTEWATER REUSE

  24. Reuse is for • 54% refill recreational lakes, • 31% green areas irrigation (6,500ha), • 5% car washing and fountains • Environmental restoration, • 8% industrial uses (Cooling)

  25. The Tula Valley, Description • Semiarid area • Pluvial precipitation: 525 mm (5 months per year) • evaporation rate: 1,750 mm • Original 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

  26. 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¡¡¡

  27. 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

  28. 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

  29. Tula Valley withoutwastewaterforirrigation

  30. Tula with a “wastewater river” for irrigation

  31. 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

  32. 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?

  33. 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

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

  35. Excessive water demand in a limited area -Water efficient Use - Water Reuse - Urban Growiing balnace with the local water availability 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 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 Non intentional Reuse of treated and non treated wastewater Reintegrating used water concept rather than disposal concept 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 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 • Urban Septic tanks • Discharge partially treated wastewater • In Sana’a, Yemen represent 80% of the urban recharge • NEW SOLUTIONS FOR ON SITE TREATMENT Leaks in the water network From 8-60% MAINTENANCE OF URBANINFRASTRUCTURE Sewers: Infiltration As high as 500 mm/yr in highly populated urban areas SEWERS MAINTENANCE Subsurface storage tanks ( gasoline, oil or chemical compounds) leak Especially if they are > 20 years old MONITORING AND MAINTENANCE PROGRAM • 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

  36. 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

  37. Water NetworkIANAS Dr. José Galizia Tundisi Dra Blanca E Jiménez Cisneros

  38. 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.

  39. Meeting in Domingo, 29 February to 01 March 2008 • Argentina, Raul Lopardo • Bolivia, Fernando Urquidi • Venezuela, Ernesto Gonzalez • Brazil, Jose GaliziaTundisi • Canada, Keith Hipel • Cuba, Mercedes Arellano Guatemala, Manuel Basterrechea Haiti, Wilson Celestin Nicaragua, Katherine Vammen Peru Adolfo Toledo and Axel Dourojeani Dominican R., Rafael Osiris de Leon Trinidad & Tobago, Vincent Cooper United States, Henry Vaux

  40. 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

  41. IN SEVERAL CASES THERE ARE > 1 author

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