Andrea Prichard, University of ArizonaDr. Christopher Scott, U of APrescott Vandervoet, U of ADr. Sharon Megdal, U of A
DROUGHT AND URBANIZATION: WATER SUPPLY CHALLENGES
OF NOGALES, SONORA
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Arizona Hydrological Society SymposiumSeptember 1-4 2010
http://mwsu-bio101.ning.com/forum/topics/a-sonoran-desert-community
Outline
• Local water challenges of Nogales, Son.– Projected rise in demand and decline in supply
– Infrastructure limitations
– Seasonal flooding
– Water quality concerns
• Current approaches to meet these challenges:– Augmentation strategies
– Increased wastewater treatment, infrastructure
– Flood dams, urban planning
– Water quality testing, improved infrastructure 2
Nogales, Sonora
• Upstream of Nogales, Arizona via Nogales Wash
• Several unplanned communities in floodzones• Dependent on groundwater• Demand on Santa Cruz Aquifer exceeds natural recharge in Sonora
Mexican Aquifers in Nogales designated as overexploited
Nogales
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Regional climate change projections include:
• Increased intensity of precipitation events
• +2 degrees Celsius by 2050
• 5‐15% decline in rainfall by 2050 (IPCC 2007)
Monsoon
Climate and Precipitation
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• 47% of water supply imported from the Los Alisos watershed.
• Sonoran recharge of the Santa Cruz Aquifer not balanced with demand
• Severe drought this decade
• Reduced precipitation projected
• Water demand is growing with the population
Population of Ambos Nogales 1900‐2000 Pick et al 2002
Water Balance
OOMAPAS 20085
http://app1.semarnat.gob.mx/dgeia/informe_2008_ing/06_agua/cap6_2.html
SONORAARIZONA
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Conservation and Augmentation
• Tandeo implementation
(intermittent water supply)
• Older pipes leak 30‐50%
• Prioritization of water uses
• Water augmentation via interbasin transfers
Nogales Tandeo Zones OOMAPAS 2008
3hr/day
Variable
24hr/day
http://www.facebook.com/group.php?gid=248630303072&v=info
Opposition to Tandeo
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Los AlisosAquifer
Santa Cruz Aquifer
Nogales Wash Aquifer 23%
Arizona
Sonora
Nogales, Sonora’s Municipal Water Source
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30%
47%
Water Sources
• Groundwater is pumped from the following aquifers:– 339 lps (7.74 MGD) from Los Alisos (inter‐basin transfer)
– 213 lps (4.86 MGD) from Santa Cruz (binational)– 169 lps (3.86 MGD) from Nogales Wash (recharged in part by leaky pipes)
(Watergy 2008, OOMAPAS 2008, Gomez & Salas 2003)
Water from Los Alisos
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EFFLUENT
• Excessive wastewater flows from Sonora to the NIWTP
• Los Alisos Wastewater Treatment Plant planned to treat about 40% of Nogales’s sewage.
• Mexican effluent rights and the Santa Cruz riparian ecosystem
10Morehouse, Carter, and Sprouse 2000
Water Quality • A new Sonoran plant will service 6 colonias that do not have
coverage. (EPA 2009) • Pollution sources: industrial waste and sewage
• E. coli, ammonia, chlorine, and dissolved copper exceed surface water quality standards. (March 2009 ADEQ)
• Infrastructure projects underway: – Wastewater collection system rehabilitation project– Water supply and distribution project– Solid waste projects
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Quality Testing• The maquiladora industry has been a source of volatile compounds, heavy metals, and other pollutants
‐ (Rosegrant and Schleyer 1996)
• In February 2006, an OOMAPAS‐run lab in Nogales was opened to run quality analyses of wastewater.
• Citations and Fines‐ Border 2012, April 2010
http://www.azdeq.gov/obep/download/wateren.pdf
OOMAPAS Water Quality Lab ‘06
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Colonias marginales
• The average salary of Nogales,SON is 1/7 that of Nogales, AZ
• Maquiladoras provide 20% of the city’s employment
• 75% of maquila workers not from Nogales (Varady and Morehouse 2004).
• The 2020 population may double 2000’s population
• Informal communities often develop on the fringes of the city, and lack potable water and sewerage connections 13
Public Utilities and Low‐Income Housing
• Mini‐wastewater treatment facilities• Casas de interes social – low‐income housing• Colonia Colosio potable water extension
Pipa truck refillingNew housing with water tanks
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• Municipal sanitation coverage: 88%• Potable water connections: 85% • 24‐hour coverage: 39% ‐(OOMAPAS 2006)
• Pipas (water trucks)
Flooding in Nogales, Sonora
•Dangerous
•Property damage
•Infrastructure damage
•Erosion
•Spreads toxins, garbage, and pathogens
•Impacts Arizona
2008 Flood Damage
15Santa Cruz County Flood Control District
Damaged infrastructure results in sediment clogging of the sewage conveyance.
Photo from IBWC
Overflowing manhole from sewage backup
Damaged stormwater conveyance tunnel
16GNEB City of Nogales 2009
Flood Control
Gabion detention basins recently constructed to reduce peak flow and damage
5 de Febrero detention feature after precipitation event on August 21, 2010
IMIP Nogales17
The effect of detention basins on peak flow in urban environments
Hydrographshttp://serc.carleton.edu/images/introgeo/socratic/examples/Hydrograph.jpg
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Int’l Border
CAPULINES
MAQUILADORAS
CHIMENEAS
Completed gabion dams (green) and proposed dams/detention basins (orange)
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1012 11
131514
16 1718
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201 2
4
53
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IMIP 19ADEQ
Conclusion• Water demand is rising quickly; augmentation comes in the
form of inter‐basin transfers.
• Current infrastructure projects, when completed, will greatly reduce leakage, improve quality, and increase coverage.
• Flooding is a costly and dangerous problem each year, and project completion and development coordination are required for mitigation.
• City planners, engineers, and community organizations are working on sustainability measures to address the problems of rapid urbanization of this water‐limited city.
Andrea Prichard ‐[email protected]
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