Wastewater use in irrigated agriculture closing the rural urban rural water loop
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Wastewater 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. Wastewater Use in Irrigated Agriculture: Closing the Rural-Urban-Rural Water Loop

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Wastewater 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


Wastewater 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

University of Arizona


Scarcity & 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


Sobering 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.


Urban 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.

  • Africa’s urban population growth rates among the highest in the world.

  • Latin America has been predominantly urban for generations.


Urban Water Supply Growth

Millennium Development Goals face resource constraints (water, investment). Progress towards sanitation goals lagging behind water supply; therefore, wastewater management is critical.


Definitions

  • Wastewater = partially treated or untreated urban sewage

  • Effluent = treated to secondary or tertiary levels (with or without disinfection)


Rural-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)


Rural-Urban-Rural Loop Typology


Hyderabad, India

Sampling Transects

III – rural (25 – 40 km)

II – periurban (10 – 25 km)

I – urban (0 – 10 km)


Hyderabad Water Footprint


Hyderabad Water Supply/ Demand


Wastewater 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


+40 Km

Hyderabad


Coliforms in WastewaterDec. 03 – Jan. 05 (red squares = mean value)


Nematode Eggs in Wastewater


Nematode Prevalence in Farmers


Sediment Sampling

Mean egg load per 1 kg of sediment:

410,000 (SD: 240,000)


Amberpet

Nagole

Pirzadiguda

Mutialguda

Koremalla

Pillaipalli

High Court

Heavy Metals in Sediment

Source: Gerwe, Caroline. An Assessment of Heavy Metals Contamination in the Wastewater-Irrigated Area of the Musi River


Dissolved Nitrogen


Dissolved Oxygen


Total Dissolved Solids


TDS Seasonal Variation


TDS Conceptual Model


Irrigation Adapts to Constant Flow


Mexico City Water Footprint

26%


Mexico City Wastewater Sources/Fate


Tula Irrigation District


Nutrient Uptake, Salt Concentration


Monterrey-Bajo Río San Juan Swap

Falcon Reservoir

Marte R. Gómez Reservoir

McAllen, Texas

Bajo Río San Juan Irrigation District

Tamaulipas

El Cuchillo Reservoir

47%


El Cuchillo

  • Constructed in 1993

  • Supplies 5 m3/s to Monterrey (to be increased to

10 m3/s)

  • MR Gómez reservoir impacts


Negotiated 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


Effluent – 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)


BRSJ Irrigation Water Productivity


BRSJ Irrigation Efficiency

But, growing upstream demand and capture of wastewater; will need to pipe it 100+ km.


Wastewater Use: Conclusions

  • Urban growth + high tertiary treatment costs = increasing agricultural reuse

  • Promote beneficial agricultural reuse

  • Mitigate health and environmental risk


Risk 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.:


Treatment for Compliance

  • WHO - 103 faecal coliforms/100 ml

    • Cost of treating raw sewage used for direct irrigation to meet WHO standard is approx US$125 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. US$450,000 per case of infection prevented (Fattal, Shuval, Laempert, 2004).


Policy 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


Wastewater Use in Irrigated Agriculture

  • http://www.cabi.org/bk_BookDisplay.asp?PID=1785

  • 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


Kenya

Ghana

Vietnam

Pakistan

Senegal

India

Bolivia

Mexico

Jordan

Tunisia

Case Studies in the Book

Formal programs of planned reuse with treatment


Thank you.

Christopher Scott

[email protected]

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


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