On-farm Water Management: from efficiency to productivity

Theib OweisDirector of Integrated Water & Land

Management ProgramInternational Center of Agricultural

research in the Dry Areas

Why improving efficiency?

Increased water scarcity

Declining agricultural water

Need for more food Sustaining the

ecosystems Water for other

sectors

85 8070

53

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1990 2000 2025 2050

Cub

ic m

eter

per

cap

ita

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% o

f tot

al w

ater

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urce

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% Agriculture share of totalTotal available water per capitaAgriculture share of water per capita

Southern Mediterranean

Output Efficiency = ------------100% Input

Same units Normally % < 100% Implies losses during the process

Efficiency

Two groups of Efficiencies

1. Irrigation systems efficiencies– Application efficiency– Convenience efficiency– Storage efficiency

2. Farm or crop use efficacies– Water use efficiency– Transpiration efficiency– Farm water use efficiency

Typical furrow irrigation system

Storage

Irrigation

Precipitation

Field water balance

Runoff

Deep percolationDrainage

Seepage

Evaporation

Transpiration

Water stored (mm)Application Efficiency ---------------------------x100% Water applied (mm)

Reflects losses in deep percolation and runoff Does not reflect root zone satisfaction

%

Water stored (mm)Storage efficiency = -----------------------------100% Water needed (mm)

Reflects how full is the root zone Ignores deep percolation %

Water delivered to farm

Conveyance eff. = ------------------------------100% Water diverted from source

• Reflects seepage, evaporation and weeds use losses

• %

Sprinkler irrigation

One can under irrigateNo DP / 100% application Eff50% storage Eff.

One can over irrigate100% storage efficiency50 % application efficiency

Trickle irrigation

• Under irrigation– Application eff. 100%– Storage eff. 50%

• Over irrigation– Application eff. 50%– Storage eff. 100%

Issues of irrigation efficiencies

Reflects the performance of irrigation system (engineering aspects)

Ignores recoverable losses ??? Nothing to do with the return to water Wrongly used to judge the whole farm water

management system

Farm Efficiencies

Production (Kg) WUE = ---------------------------- Water used ( m3)

Units are mainly production / volume of water

No standard type of production (biomass, grain, roots ???)

No standard water used (applied, stored, ET, ???)

Biomass production (kg)Transpiration Eff.= --------------------------------- Transpiration (mm)

Ignores evaporation lossesReflects plant performanceNot %

New concept (Shideed, Oweis and Gabr 2000)

Water required to produce (x) in mm Farm WUE = --------------------------------------------------100% Water used to produce (x) in mm

Reflects farmer’s performance Considers local environment specifity Can be used for farm multi-cropping %

61

45

76

3747

32

68

01020304050607080

WU

E %

Storage

Irrigation

Precipitation

Field water balance

Runoffrecoverable

Transpiration

EvaporationLosses

To ground waterrecoverable

Deep percolationDrainagePartially recoverableQuality losses

Seepagerecoverable

Issues of irrigation losses

Recoverable losses:are not real / only on paper losseseconomic issue at the farm (cost to recover)management issue at the scheme and basin+ or - environmental issues (leach out salts)

Real losses may not be recovered:EvaporationTranspiration (productive)Non beneficial uses (weeds)

Water productivity: a broader framework

ReturnWP = --------------------------------- Unit of water consumed

What return ?? Biomass, grain, meat, milk (kg) Income ($) Environmental benefits (C) Social benefits (employment) Energy (Cal) Nutrition (protein,

carbohydrates, fat)

What water ?? Quality (EC) Location (GW depth) Time available

Consumed (depleted) Evaporation Transpiration Quality deterioration

Saline water equivalent

0.0

0.5

1.0

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2.5

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Vo

lum

e o

f w

ate

r (m3 )

Irrigation water salinity (dS m–1)

Barley

Cotton

Sugar beet

Wheat, bread

Wheat, durum

Broccoli

Cucumber

Spinach

Maize

Faba bean

Oweis et al 2011

Biological WP kg/m3

0.030.3 0.2

3

10.4

0.1

1

7

3

0.81.2

0

1

2

3

4

5

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7

8

Beef Lentil Wheat Potato Olive Dates

Economic Wp $/m3

0.1 0.1 0.10.3

10.8

0.3 0.30.6 0.7

3

1.6

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Beef Lentil Wheat Potato Olive DatesNutritional WP Protein gr/m3

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90

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10 8

30

150 150

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Beef Lentil Wheat Potato Olive Dates

Nutritional WP Calories/m3

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1150 1120

210

35004000

7000

3450

2240

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Beaf Lentil Wheat Potato Olive Dates

Potential water productivityimprovement

Scales and drivers to increase WP

At the basin level: competition among uses (Env., Ag.,

Dom.) conflicts between countries Equity issues

At the national level: food security hard currency sociopolitics

At the farm level: maximizing economic return Nutrition in subsistence farming

At the field level: maximizing biological output

Tradeoffs between water & land productivity

y = -0.4278x2 + 4.7328x - 0.543

R2 = 0.7611

0

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0 2 4 6 8 10

Land productivtiy (t/ha)

Wa

ter

pro

du

cti

vty

(k

g/m

3 x

10

)

Max WP

Max

Yield

Potential WP improvements

Reducing evaporation Improving management Enhancing genetic

resources Great potential in

developing countries

What to grow under scarcity ??

• Traditional farming: hard to change• Water productivity: what productivity ??• National food security,

self sufficiency • Virtual water ???

1

0.5

0.050.1

1

0.25

0

0.2

0.4

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0.8

1

1.2

Wheat Dates Beef

Kg/ m3US$/ m3

Potential practices

Supplemental irrigation

Deficit irrigationGermplasmCultural practicesWater harvesting

Irrigated agriculture

• Increasing water productivity– Deficit irrigation– Modifying cropping patterns– Cultural practices

• Management of marginal water and soil– Secondary salinity – Reuse of treated wastewater

• Improving irrigation systems performance

Modernizing irrigation: water savings !

Does irrigation modernization save water ?

YES Does increasing Irrigation Efficiency from 50% to 80% save

30% water?

NO How much saving then? Depends on:

System changed and system adopted Irrigation management Crops and pattern Mostly in reducing evaporation and non beneficial use Needs assessment

Is it worth the cost? Needs research

Modern systems: productivity

• Higher productivity is not only associated with water savings. Drip irrigation does:– Provide better soil water due to frequent irrigation– Fertigation more frequent and uniform– Weed control through

• The cost:– Investment, Maintenance, Skill– Salt accumulation needs periodical flushing

• Modernizing surface irrigation, very good idea