Presentation on theme: "Wastewater use in irrigated agriculture: closing the rural-urban- rural water loop Presented at Departmental Seminar Series (Soil, Water & Environmental."— Presentation transcript:
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 urban-rural population threshold… 750 million urban Indians by 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.
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 Rural sourceUrban useRural 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
Hyderabad, India Sampling Transects III – rural (25 – 40 km) II – periurban (10 – 25 km) I – urban (0 – 10 km)
Coliforms in Wastewater Dec. 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)
Heavy Metals in Sediment AmberpetNagole High Court PirzadigudaMutialgudaKoremallaPillaipalli Source: Gerwe, Caroline. An Assessment of Heavy Metals Contamination in the Wastewater-Irrigated Area of the Musi River
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 R í o San Juan Swap Tamaulipas McAllen, Texas Marte R. Gómez Reservoir El Cuchillo Reservoir Falcon Reservoir Bajo Río San Juan Irrigation District 47%
El Cuchillo Constructed in 1993 Supplies 5 m 3 /s to Monterrey (to be increased to 10 m 3 /s) MR Gómez reservoir impacts
Negotiated Settlement 9 Oct – Monterrey, federal and Nuevo León governments agree to finance and construct El Cuchillo dam 6 Sept –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 m 3 /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 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 PID=1785 PID=1785 DO_TOPIC.html DO_TOPIC.html Introduction: management challenges Typology and global assessment Livelihoods the key driver WHO health guidelines Cost of guidelines compliance
Case Studies in the Book Kenya Ghana Vietnam Pakistan Senegal India Bolivia Mexico Jordan Tunisia Formal programs of planned reuse with treatment
Thank you. Christopher Scott 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