Wastewater use in Wastewater use in irrigated irrigated agriculture: agriculture: closing the rural-closing the rural-urban-rural water urban-rural water looploopPresented at Departmental Seminar Series (Soil, Water & Environmental Science), University of Arizona, 19 February 2007

Wastewater Use Wastewater Use in Irrigated in Irrigated Agriculture:Agriculture:

Closing the Rural-Urban-Closing the Rural-Urban-Rural Water LoopRural Water Loop

Christopher ScottChristopher ScottUdall Center for Studies in Public Policy, andUdall Center for Studies in Public Policy, and

Dept. Geography & Regional DevelopmentDept. Geography & Regional DevelopmentUniversity of ArizonaUniversity of Arizona

Scarcity & Competition Scarcity & Competition for Waterfor 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 DemographicsSobering 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 ExplosionUrban 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 Urban Water Supply GrowthGrowth

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

DefinitionsDefinitions

Wastewater = partially treated or untreated urban sewage

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

Rural-Urban-Rural Water Rural-Urban-Rural Water LoopLoop 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 Rural-Urban-Rural Loop TypologyTypologyRural 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

Hyderabad, IndiaHyderabad, India

Sampling Transects

III – rural (25 – 40 km)

II – periurban (10 – 25 km)

I – urban (0 – 10 km)

Hyderabad Water Hyderabad Water FootprintFootprint

Hyderabad Water Supply/ Hyderabad Water Supply/ DemandDemand

Hyderabad Water Supplies and Demands

Osman Sagar Himayat SagarGround Water

Singur

Manjira

Krishna river

Godavari

extra needed (demand - total supply)

0

10

20

30

40

50

60

70

80

90

100

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

2010

2015

2020

2025

2030

time (years)

Milli

on C

ubic

Met

ers

per M

onth

Wastewater Wastewater BiogeochemistryBiogeochemistry 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

Hyderabad +40 Km

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

0

1

2

3

4

5

6

7

8

9

0 5 10 15 20 25 30 35 40

Distance downstream from Hyderabad (km)

LO

G E

.col

i (CFU

100

ml-1

)

Nematode Eggs in Nematode Eggs in WastewaterWastewater

0

20

40

60

80

100

120

140

I II IIISample Point

Ova

litre-

1

Hookworm

Ascaris

Trichuris

Nematode Prevalence in Nematode Prevalence in FarmersFarmers

0

10

20

30

40

50

60

70

I (n=240) II (n=354) III (n=413)Sample point

Pre

vale

nce

(%)

HookwormAscarisTrichuris

Sediment SamplingSediment Sampling

Mean egg load per 1 kg of sediment: 410,000 (SD: 240,000)

Heavy Metals in Heavy Metals in SedimentSediment

0.0

0.2

0.4

0.6

0.8

1.0

1.2

-10 -5 0 5 10 15 20 25 30 35

Distance Downstream from Amberpet Bridge (km)

No

rmal

ized

Met

al C

on

cen

trat

ion

(--

-)

Copper Zinc Cadmium Lead

Amberpet NagoleHigh Court Pirzadiguda Mutialguda Koremalla Pillaipalli

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

Dissolved NitrogenDissolved Nitrogen

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40

Distance downstream from Hyderabad (km)

Disso

lved

nitro

gen

conc

entrat

ion

(mg

l-1)

Dissolved OxygenDissolved Oxygen

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

0 5 10 15 20 25 30 35 40

Distance downstream from Hyderabad (km)

DO

con

cent

ration

(m

g l-1

)

Total Dissolved SolidsTotal Dissolved Solids

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 5 10 15 20 25 30 35 40

Distance downstream from Hyderabad (km)

Salin

ity

conc

entrat

ion

(dS

m-1)

TDS Seasonal VariationTDS Seasonal Variation

800

1000

1200

1400

1600

1800

2000

2200

0 10 20 30 40Distance from Hyderabad (km)

TD

S (

mg

l-1)

Maximum, April Minimum, August Annual mean

City Rural Threshold sensitivity for rice = 2010 mgl-1

TDS Conceptual ModelTDS Conceptual Model

Hyderabad

Urban drainage

Rural drainage

Irrigated fields

W ater quality sampling points

Irrigation divers ion

Urban dra inage

Rura l dra inage

Return flows

Q in,C in

Q i,C i

Qd,Cd

Qout,Cout

Qu,Cu

Qr,Cr

E

E

I II III IV V VI VIIIVII

E E E E E

E Evaporation

Qbd,CbdQbu,Cbu

Irrigation Adapts to Irrigation Adapts to Constant FlowConstant Flow

0

10

20

30

40

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Flo

w (

Mm

3)

Irrigation abstractions Flow at Amberpet

Mexico City Water Mexico City Water FootprintFootprint

26%

Mexico City Wastewater Mexico City Wastewater Sources/FateSources/Fate

Source/Fate Flow (m3/s)

Comments

Wastewater generated in Mexico City

45 194 l/s/cap. At 70% return rate, water supply is 260 l/s/cap.

Primary treatment for irrigating parks/green areas within Mexico City

10 Could irrigate upto 10,000 ha of land, but may be used to maintain wetlands and “floating gardens.”

Primary and secondary treatment for Texcoco Lake Reclamation

1.0 ~ 1.5 Reclamation of sodic soils, reforestation, and Nabor Carillo Lake.

Tertiary treatment for animals and/or groundwater injection, Texcoco Lake

0.05 Sedimentation, flocculation, filtration (sand, activated carbon), chlorination.

Untreated wastewater 34 Discharged to Tula Irrigation District (Hidalgo State) through a network of tunnels, one > 60 km.

Tula Irrigation DistrictTula Irrigation District

Nutrient Uptake, Salt Nutrient Uptake, Salt ConcentrationConcentrationHead-Tail Water Quality Trends, Tula Irrigation District 003, Mexico

0

200

400

600

800

1000

1200

1400

1600

1800

Head Middle Tail

EC

(m

icro

mho

s)

0

2

4

6

8

10

12

Nut

rient

s, 0

.1*B

OD

(m

g/L)

EC

Nitrogen (dry)

Nitrogen (rains)

0.1*BOD (rains)

0.1*BOD (dry)

Phosphates (rains)

Phosphates (dry)

Monterrey-Bajo RMonterrey-Bajo Ríío San o San Juan SwapJuan Swap

Tamaulipas

McAllen, Texas

Marte R. Gómez Reservoir

El Cuchillo Reservoir

Falcon Reservoir

Bajo Río San Juan Irrigation District

47%

El CuchilloEl Cuchillo Constructed in 1993 Supplies 5 m3/s to Monterrey (to

be increased toMarte R. Gomez vs. El Cuchillo Reservoir Storage (1993-2004)

y = 0.5015x + 31.7

0

100

200

300

400

500

600

700

0 200 400 600 800 1000 1200

El Cuchillo (MCM)

Mar

te R

. Gom

ez (M

CM

) 10 m3/s) MR

Gómez reservoir impacts

Negotiated SettlementNegotiated 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 Effluent – the Bargaining ChipChip 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 BRSJ Irrigation Water ProductivityProductivityYear Total Production Total Gross Total Net Gross Water Net Water

Volume Used Volume Used Productivity Productivity

(Ton) (Thousand m3) (Thousand m3) (Ton/Thousand m3) (Ton/Thousand m3)

95-96 202,131.86 263,331.00 146,743.00 0.77 1.38 96-97 101,029.00 146,811.00 78,927.00 0.69 1.28

97 - 98 175,891.00 222,875.00 128,059.00 0.79 1.37 98 - 99 84,614.00 114,272.00 64,089.00 0.74 1.32 99 - 00 90,555.00 110,100.00 64,201.00 0.82 1.41 00 - 01 6,609.00 160,499.00 83,283.00 0.04 0.08 01 - 02 250,578.00 383,171.00 219,372.00 0.65 1.14

02 - 03 281,786.20 395,429.90 213,457.40 0.71 1.32

03 - 04 394,543.58 217,267.50 110,089.20 1.82 3.58

BRSJ Irrigation EfficiencyBRSJ Irrigation EfficiencyIrrigation District 026 Bajo Rio San Juan

0

100

200

300

400

500

600

1989-1

990

1990-1

991

1991-1

992

1992-1

993

1993-1

994

1994-1

995

1995-1

996

1996-1

997

1997-1

998

1998-1

999

1999-2

000

2000-2

001

2001-2

002

2002-2

003

2003-2

004

2004-2

005

Irrigation Season

Res

ervo

ir W

ater

Del

iver

y (M

CM

)

(10,000)

10,000

30,000

50,000

70,000

90,000

110,000

130,000

150,000

Irri

gate

d A

rea

(ha)

Reservoir Water Release

Irrigated Area

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

Wastewater Use: Wastewater Use: ConclusionsConclusionsUrban growth + high tertiary treatment costs = increasing agricultural reuse

Promote beneficial agricultural reuse

Mitigate health and environmental risk

Risk MitigationRisk 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 Treatment for ComplianceCompliance 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 ImplicationsPolicy 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 Wastewater Use in Irrigated AgricultureIrrigated Agriculture http://www.cabi.org/bk_BookDis

play.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

Case Studies in the BookCase Studies in the Book

Kenya Ghana Vietnam Pakistan Senegal India

Bolivia Mexico Jordan Tunisia

Formal programs of planned reuse with treatment

Thank you.Thank you.Christopher Scott

cascott@email.arizona.edu

626-4393Acknowledgements: 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 EngineeringLiqa Raschid, International Water Management Institute Daan van Rooijen, International Water Management Institute, Ghana