Title: Wastewater use in irrigated agriculture: closing the rural-urban-rural water loop
1Wastewater use in irrigated agriculture closing
the rural-urban-rural water loop
- Presented at Departmental Seminar Series (Soil,
Water Environmental Science), University of
Arizona, 19 February 2007
2Wastewater Use in Irrigated Agriculture Closing
the Rural-Urban-Rural Water Loop Christopher
Scott Udall Center for Studies in Public Policy,
and Dept. Geography Regional Development Univers
ity of Arizona
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5Scarcity Competition for Water
- Declining allocations of water to agriculture
- Rapid urban growth a global phenomenon
- Water productivity in agriculture rising (more
crop per drop) - Agriculture increasingly adapting to the use of
poorer quality water for irrigation
6Sobering Demographics
- 880 million additional population by 2015,
virtually all in developing countries. - After 2015, all worldwide growth in population
will take place in developing country cities.
7Urban Explosion
- India will soon cross the 50-50 urban-rural
population threshold 750 million urban Indians
by 2050. - China is actively planning for cities each with
more than 100 million population. - Africas urban population growth rates among the
highest in the world. - Latin America has been predominantly urban for
generations.
8Urban Water Supply Growth
Millennium Development Goals face resource
constraints (water, investment). Progress towards
sanitation goals lagging behind water supply
therefore, wastewater management is critical.
9Definitions
- Wastewater partially treated or untreated urban
sewage - Effluent treated to secondary or tertiary
levels (with or without disinfection)
10Rural-Urban-Rural Water Loop
- Transfer of water from agriculture to cities
- Physically, often entails inter-basin transfers
- Water rights, property regime, economic issues
- Urban use, quality degradation depletion
- Salinity load, even with (because of?) treatment
- Public health risk (consumers and producers)
- Agricultural end use of wastewater/ effluent
- Adapt to quality (nutrients, salinity)
- Adapt to timing (uniform throughout year)
11Rural-Urban-Rural Loop Typology
Rural source Urban use Rural end use
Production irrigated ag. Multiple (w/ urban sprawl on ag.). Wastewater WW mixed source for in-formal urban periurb. ag. e.g. Hyderabad, India - Musi
Small-scale rural water Multiple use. Wastewater WW primary source for production irrigated ag. e.g. Mexico City - Mezquital
Production irrigated ag. Multiple use. Effluent Same ag. users as source water (i.e., water swap with treatment). e.g. Monterrey, Mex. Bajo Rio San Juan
12Hyderabad, India
Sampling Transects III rural (25 40 km) II
periurban (10 25 km) I urban (0 10 km)
13Hyderabad Water Footprint
14Hyderabad Water Supply/ Demand
15Wastewater Biogeochemistry
- Microbial attenuation and infection
- Coliform die-off
- Nematode (hookworm) egg deposition
- Heavy metals attenuation ( uptake?)
- Deposition, re-suspension
- Nutrient attenuation plant uptake, eutrophicn.
- Dissolved solids concentration, deposition
- Irrigation diversion, evaporation, return flow
1640 Km
Hyderabad
17Coliforms in WastewaterDec. 03 Jan. 05 (red
squares mean value)
18Nematode Eggs in Wastewater
19Nematode Prevalence in Farmers
20Sediment Sampling
Mean egg load per 1 kg of sediment 410,000 (SD
240,000)
21Heavy Metals in Sediment
Source Gerwe, Caroline. An Assessment of Heavy
Metals Contamination in the Wastewater-Irrigated
Area of the Musi River
22Dissolved Nitrogen
23Dissolved Oxygen
24Total Dissolved Solids
25TDS Seasonal Variation
26TDS Conceptual Model
27Irrigation Adapts to Constant Flow
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30Mexico City Water Footprint
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31Mexico City Wastewater Sources/Fate
32Tula Irrigation District
33Nutrient Uptake, Salt Concentration
34Monterrey-Bajo Río San Juan Swap
Falcon Reservoir
Marte R. Gómez Reservoir
McAllen, Texas
Bajo Río San Juan Irrigation District
Tamaulipas
El Cuchillo Reservoir
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35El Cuchillo
- Constructed in 1993
- Supplies 5 m3/s to Monterrey (to be increased to
- 10 m3/s)
- MR Gómez reservoir impacts
36Negotiated Settlement
- 9 Oct. 1989 Monterrey, federal and Nuevo León
governments agree to finance and construct El
Cuchillo dam - 6 Sept. 1990 Tamaulipas, federal and Nuevo León
governments agree to rationalize water use,
preserve multiple uses of BRSJ irrigation water
37Effluent the Bargaining Chip
- Federal CNA allocates 189 MCM (6 m3/s) of
effluent from Monterrey to BRSJ irrigators - Nuevo León assumes responsibility and cost of
treatment in compliance with federal water
quality standards - Rehabilitation of the Anzaldúas-Rhode pumping
station on the Río Bravo - Relocation of downstream Tamaulipas urban water
demand from MR Gómez reservoir (Rhode canal)
38BRSJ Irrigation Water Productivity
39BRSJ Irrigation Efficiency
But, growing upstream demand and capture of
wastewater will need to pipe it 100 km.
40Wastewater Use Conclusions
- Urban growth high tertiary treatment costs
increasing agricultural reuse - Promote beneficial agricultural reuse
- Mitigate health and environmental risk
41Risk Mitigation
- Secondary treatment (biosolids handling
enforcement is essential) - Application method to limit irrigators exposure
- Market wash water and handling
- Crop restrictions non-edible and fodder. Limit
fresh produce irrigation, e.g.
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43Treatment for Compliance
- WHO - 103 faecal coliforms/100 ml
- Cost of treating raw sewage used for direct
irrigation to meet WHO standard is approx US125
per case of infection (of hepatitis, rotavirus,
cholera, or typhoid) prevented (Fattal, Shuval,
Laempert, 2004). - USEPA zero incremental risk
- Incremental cost of further treating wastewater
from WHO to USEPA standard approx. US450,000 per
case of infection prevented (Fattal, Shuval,
Laempert, 2004).
44Policy Implications
- Planned reuse offers no easy solutions
- Key to success are
- coherent legal and institutional framework
- coordination of multiple government agencies
- flexible application of the polluter pays
principle - extension to farmers of appropriate practices for
wastewater use - public awareness campaigns to build social
acceptability for reuse
45Wastewater Use in Irrigated Agriculture
- http//www.cabi.org/bk_BookDisplay.asp?PID1785
- http//www.idrc.ca/en/ev-31595-201-1-DO_TOPIC.html
- Introduction management challenges
- Typology and global assessment
- Livelihoods the key driver
- WHO health guidelines
- Cost of guidelines compliance
46Case Studies in the Book
- Kenya
- Ghana
- Vietnam
- Pakistan
- Senegal
- India
- Bolivia
- Mexico
- Jordan
- Tunisia
Formal programs of planned reuse with treatment
47Thank you.
- Christopher Scott
- cascott_at_email.arizona.edu
- 626-4393
- Acknowledgements
- Stephanie Buechler, UA Bureau of Applied
Research in Anthropology - Pay Drechsel, International Water Management
Institute, Ghana - Jeroen Ensink, London School of Hygiene and
Tropical Medicine - Naser Faruqui, International Development
Research Centre - Francisco Flores, Cornell University
- Jesús R. Gastélum, UA Dept. of Civil Engineering
- Liqa Raschid, International Water Management
Institute - Daan van Rooijen, International Water Management
Institute, Ghana