a global assessment of water

(1)

Passer à la première page

Water scarcity and food security : a global assessment of water

potentiality in Tunisia

Jamel Chahed, Mustapha Besbes, Abdelkader Hamdane**

* National Engineering School of Tunis, BP N 37, Le Belvedere, 1002 Tunis Tunisia

** Agronomic Institut de Tunis, Tunisie, Av. Charles Nicolle, Tunis, Tunisia jamel.chahed@enit.rnu.tn

mbf.besbes@gnet.tn

Abdelkader.hamdane@gmail.com

4º Marcelino Botin Water Workshop,

Santander, September 22-25, 2009

(2)

Passer à la

References



Besbes M., Chahed J., Hamdane A. (2007), Bilan intégral des ressources en eau de Tunisie, sécurité hydrique et sécurité alimentaire, Communication at Académie d’Agriculture. Paris, séance du 4-4-2007 (l’Avenir des Eaux

Continentales)



Chahed J., Hamdane A., Besbes M.,(2007), Bilan intégral des ressources en eau de Tunisie, sécurité hydrique et sécurité alimentaire, La Houille

Blanche N°3,2007



Chahed J., Hamdane A., Besbes M.,(2008), A Comprehensive Water

Balance of Tunisia: Blue Water, Green Water, Virtual Water, Water

International, 33:4, pp. 415-424

(3)

Pluvial water resources

36000 Mm

3

225 mm/year Withdrawl water resources

4850 Mm

³

< 500 m3/cap/year

• Surface water : 2700 Mm

³

• Ground water : 2150 Mm3 Withdrawal resources

3150 Mm

³

600 Mm

³

Reserve for drought

+120 Mm

³

EUT (Treated Waste Water)

Average rainfall

Tunisian water resources

(4)

Source: L.Frigui & Annuaire Hydrologique, DGRE, Tunis

Surface water Ground Water

éch:

500 M m³/an éch:

500 M m³/an

Données DGRE

L.Frigui & Annuaire Hydrologique, DGRE,

Data DGRE es DGRE Donné éch:

360 M m³/an

Water uses

Source: DGGR,DGRE

(5)

• is limited

~ 500 m

³

/Cap/year

• is non uniformly distributed - In space

- In time

• is largely exploited (~ 80 %)

Water resource

Water uses

Tunisian water resources : Transfers and Water uses

Drinking Water: 300 Mm

³

≈ (30 m

³

/Cap/year) Industrial Water: 100 Mm

³

≈ (10 m

³

/Cap/year) Tourist Water : 20 Mm

³

≈ (2 m

³

/Cap/year)

Agriculture : 2100 Mm

³

≈ (210 m

³

/Cap/year)

(6)

Tunisie : ressources en eau et répartition

DIRECTEMENT UTILISE 1620 Mm3 (180 m3/ hab/an)

DIRECTLY USED

1620 Mm3 (180 m3/ hab /an)

NON UTILISE

955 Mm3

UNUSED

955 Mm3

470

UTILISATION DIFFEREE 470 Mm3

WATER RESERVE 470 Mm3

Evaporation in dams [ 80] Allocated and unused [ 170]

Allocations PPI non utilisées [ 240]

Network losses Sonede [ 85]

Network losses (irrigation) [ 620]

Irrigation [ 83% ]

Industries [4%]

Collectivities [12%]

Aquifer recharge [ 1%]

For Draught [ 470]

1620

955

Clousure Error [ 70 ]

70

VOLUME MOBILISE

3115 Mm3 (346 m3/ hab/an)

WITHDRAWN WATER

3115 Mm3 (346 m3/ hab year)

Statement 1: Irrigation consumes a large part of water resources



Direct water uses

(collectivities, tourism,

industry) represent less than 20 % of water uses.



Agriculture water uses

represent more than 80 % of water uses.



Irrigation occupies less than

1/10 of cultivated areas and

produces around 1/3 of food

production

(7)

Statement 2: «Blue Water» supply is stabilized and agricultural water allocations will be

reduced

Evolution of water resource estimation 10

⁶

m

³

1968 1972

1980 1985

1990 1996

2005

Ground Water Surface Water 0

500 1000 1500 2000 2500 3000

(8)

Passer à la

Statement 3: Equivalent-Water of foodstuffs imports is important

Foodstuffs imports-export, 10

⁶

m

³

/year, average 1990-2004

1990 19911992 19931994 19951996 1997

1998 1999 2000 2001

2002 2003 2004

Exportations Importations

Production

0 2000 4000 6000 8000 10000 12000

(9)

Statement 4: The amount of «Green Water» is considerable

Equivalent eau; Mm3/an; Moyenne 1990-2004

Import Export

Viande 1488 Viande 15 Viande

Céréales 2154 Céréales 190 Céréales

Maraîchages 110 Maraîchages 90 Légumes

Huile 1867 Huile 1100 Fruits

Sucre, café, thé 670 Sucre, café, thé 25 Huiles

AutresFruits 90 Dattes 200 Sucre, café, thé

Agrumes 25

AutresFruits 25

S u c r e , c a f é , t h é 5 %

Huiles 17%

Fruits 11%

M arket- gardening; 1305 OliveOil

1555

Dats; 700

Citrus Fruits 220

Other fruits 755

Cereals; 2515 M eat; 1920

Rainfed agriculture

-

Cereals, Olive oil…

Irrigated agriculture (Market gardening, Dats, Fruits…

Equivalent Water of Food production, 10

⁶

m

³

/year, 1990-2004

(10)

Passer à la oil; 1867

Market gardening ; 110

Cereals ; 2154 Meat; 1488

Other; 90 Sugar , cofee ,

thee; 670

Statement 5: «Green Water» plays un important part in foodstuffs trade

Foodstuffs imports, Equivalent-Water [10

⁶

m

³

/year], 1990-2004

(11)

Foodstuffs exports, Equivalent-Water [10 ⁶ m ³ /year]

Olive oil; 1100 Dates; 200

Citreous Fruits; 25 Drinks; 65

Market-gardening; 90 Other; 80

Cereals; 190

(12)

0 1000 2000 3000 4000 5000

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

Imports Production

Cereals : Productions & Import (1000 tonnes)

Source: Annuaire des statistiques agricoles , MARH.

(13)

Rainfall (North) versus cereals production

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

Cereales Pluie mm

0 100 200 300 400 500 600 700 800

mm

Source: Annuaires Pluviométriques , DGRE & Annuaire des statistiques agricoles , MARH.

(14)

Passer à la première page 1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

Olives Céréales 0

500 1000 1500 2000 2500 3000

Rainfed agriculture production (1000 tonnes)

Source: Annuaires des statistiques agricoles , MARH.

(15)

Foodstuffs exports in value [%]

Sea products 20%

dates 11%

Citreous fruits 2%

Olive oil 46%

cereals 7%

Wine and drinks 3%

other 11%

(16)

Foodstuffs imports in value [%]

Meat

3% Milk

8%

Durum 7%

Wheat 20%

Barley Corn 4%

Potato 8%

2%

Oil 15%

Thee coffee 6%

Sugar 14%

Other 13%

(17)

Coverage rate of foodstuffs trade balance [%]

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

0 10 20 30 40 50 60 70 80 90

Value

Equivalent-Water

(18)

Passer à la

Global Water Demand in average year

Sector Water demand

10

⁹

m3/year

Irrigation 2,1

Rainfed agriculture [Green Water] 6 Deficit of food balance[Imported Vitual Water] 3,7

Urban [Cities, tourism] 0,4

Industry 0,1

Forests and Rangelands 5,5

Water Bank [Storage in dams for droughts] 0,6 Environment [conservation of humid areas] 0,1

Total Water Demand 18,5

Foodstuffs Demand (Equivalent-Water)

≈ 1/6 irrigated Agriculture (Bleu Water)

≈ 1/2 rainfed Agriculture (Green Water)

≈ 1/3 Foodstuffs import (Virtual Water)

(19)



Water resources and food safety : An important part of withdrawal water «Blue Water» is used in agriculture (more than 80%)



Mobilized «Blue Water» is stabilized and agricultural water allocations will be reduced



Rainfed agriculture plays un important role in food security : the amount of equivalent water «Green Water» is considerable (~ 1/2 of foodstuffs water FP); its role in food trade balance is crucial : it

contributes to 2/3 of the national agricultural production and 80% of the agricultural exports



The foodstuffs balance indicates that the “Equivalent water” budget

«Virtual Water» is important (~1/3 of foodstuffs water FP)

The established facts of water resource

development and management in Tunisia

(20)

Passer à la

Trends in agricultural water use, 1990–2006

467370 449825

433145 417285

402200 377968

353282 334700

Irrigated area ha

4355 4575

4809 5058

5323 5666

6020 6320

Water use allocation m³/ha

2030 2025

2020 2015

2010 2005

2000 1996

Year

Eau 21 Projection

"Eau 21, Long term water strategy in Tunisia, 2030", Min. Agr., 1998

(21)

Rainfed agricultural evolution, 1960–2007

Wheat cultivated area [ha]

0 200000 400000 600000 800000 1000000 1200000 1400000

1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

(22)

Passer à la

Rainfed agricultural evolution, 1960–2007

Wheat Production [Tones]

0 500000 1000000 1500000 2000000 2500000

1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

(23)

Modeling long term water demand and resources

Trend Scenarios (horizons 2025 -2050)

Based on classic management of «Blue Water»

- Simulation 1 : optimistic

- drastic control of all water uses

- low increase water demand for direct uses

- low increase of the equivalent water of food demand

- Simulation 2 : realistic

- drastic control of all water uses

- reasonably increase of water demand

- improve in the equivalent water related to food demand

(24)

Value Equivalent-Water

Water requirements for food production in Europe per Capita per year

m³/year

1642 1460

730

365 182 547 912

1277 1095

500 700 900 1100 1300 1500

1960 1970 1980 1990 2000

Water requirements for food production in Tunisia per Capita per year

data : FAO www.fao.org/countryprofiles & INS Tunisie

(25)

Meet consumption kg/capita/year : (except fish an sea products), 2000

20

90

120

0 20 40 60 80 100 120

Tunisia France USA

(26)

Passer à la

Modeling long term water demand and resources

Sustainable Scenario (horizons 2025 -2050)

Based on a global water vision including (Blue Water, Green Water, Virtual Water).

- Hypothesis as in Simulation 2 : realistic

- drastic control of all water uses

- reasonably increase of water demand

- improve in the equivalent water related to food demand

- Concrete development of rainfed agriculture (Green Water)

-

(27)

Modeling Food Demand Water Footprint

IW : Irrigation Water Volume

EWR : Exploitable Water Resources (EWR) « Blue Water » DD : Direct Water Demand (collectivities, tourism, industry) ; RI : Rate of Water Recycling

ENV : Environmental Water demand

Irrigation Water Volume at constant flux

ENV DD

) RI 1

( EWR

IW    



The direct demand (drinking water, industry) is incompressible and increases with the population.

Consequently, irrigation allowance is adjusted to the quantity of blue

water available when the direct water demand has been satisfied :

(28)



 



 

 EWR ( 1 RI ) DD ENV ) (

GW FD

VW       

Modeling Food Demand Water Footprint

FD : Equivalent Water Demand for Food

GW : Equivalent-Water of rainfed agricultural production « Green Water » EWR : Exploitable Water Resources (EWR) « Blue Water »

DD : Direct Water Demand (collectivities, tourism, industry) ; RI : Rate of Water Recycling

: Global Irrigation Factor

VW : Equivalent-Water deficit « Virtual Water »

ENV : Environmental Water demand

Dependency Rate of Food Demand (Equivalent-Water)

FD

 VW

 VW  FD / 

Green Water Blue Water Virtual Water



(29)

Model validation 1996-2004

VW )

ENV DD

) RI 1

( EWR (

GW

FD       



 



 



Green Water Blue Water Virtual Water

1996 2004

Population [10⁶ habitants] 9,1 9.93

Exploitable Resource (EWR) [10⁶m³/year] 2880 2500 Food demand, Eq. water [m³/year/Capita] 1350 1450 Total food demand (FD) water[10⁶m³/year] 12280 14399

Direct water demand [m³/year/Capita] 45 55

Total direct water demand (DD)[10⁶m³/year] 410 546

Reuse rate, RI 0.08 0.1

Total irrigation allocation (IW) [10⁶m³/year] 2008 2008 Rainfed agriculture (GW) [10⁶m³/year] 6500 8000

Conversion factor,  0,9 0.9

Deficit of food balance (VW) [10⁶m³/year] 3982 4591

Total water demand 12695 14945

Rate of dependency 31% 31%

(30)

Modeling long term water demand and resources

Trend scenarios (horizon 2025)

Model Adjustment

2004

Simulation 1 Simulation 2

Population [10⁶ habitants] 9.93 12,15 12,15

Exploitable Resource (EWR) [10⁶m³/year] 2500 2700 2700 Food demand, Eq. water [m³/year/Capita] 1450 1600 1700 Total food demand (FD) water[10⁶m³/year] 14399 19440 20655

Direct water demand [m³/year/Capita] 55 60 70

Total direct water demand (DD)[10⁶m³/year] 546 729 851

Reuse rate, RI 0.1 0,5 0,5

Total irrigation allocation (IW) [10⁶m³/year] 2008 2336 2275 Rainfed agriculture (GW) [10⁶m³/year] 8000 8000 8000

Conversion factor,  0.9 0,9 0,9

Deficit of food balance (VW) [10⁶m³/year] 4591 9338 10608

Total water demand 14945 20169 21506

Rate of dependency 31% 46% 49%

VW )

ENV DD

) RI 1 ( EWR (

GW

FD       



 



 



(31)

Modeling long term water demand and resources

Trend scenarios (horizon 2050)

2004

Simulation 1 Simulation 2

Population [10⁶ habitants] 9.93 13 13

Reuse rate, RI 0.1 0,5 0,5

Conversion factor, k 0.9 0,9 0,9

VW )

ENV DD

) RI 1 ( EWR (

GW

FD      



 



 



(32)

Modeling long term water demand and resources

Sustainable scenario (horizons 2025 -2050)

2004

Sustainable Scenario

2025 2050

Population [10⁶ habitants] 9.93 12,15 13

Reuse rate, RI 0.1 0,5 0,5

Conversion factor,  0.9 0,9 0,9

VW )

ENV DD

) RI 1 ( EWR (

GW

FD       



 



 



(33)



Enlargement of the Water Resource notion to all

kind of the contributions to the Global Water Balance : «Blue Water», «Green Water», «Virtual Water»,

«Non-conventional Water».



Enlargement of the Demand Management notion to all kind of water uses including the water requirements for food demand



Optimization of all water uses including the water

involved in the rainfed agriculture production «Green Water», and in the international trade exchange

«Virtual Water»,

Prospects for the improvement of the

global water balance

(34)

Passer à la

Some progresses in the global water vision, may be achieved by taking into account:



the disparities between the regions of the country



the inter-annual variability of water resources



Water quality constrains : salinity, reuse of treated

water, over exploitation…

(35)

Disparities between the regions

éch:

500 M m³/an éch:

500 M m³/an

L.Frigui & Annuaire Hydrologique, DGRE, Surface Water Ground Water

Data DGRE es DGREDonné éch:

360 M m³/an

Wtar use

Source:

DGGR,DGRE

(36)

Water quality constrains

Over withdrawn aquifers (en 2000) Salinity of water table aquifers

< 1.5 g/l 1.5 à 3 g/l

> 3 g/l

(37)

Ongoing research: Global Water balance regionalization [Region (i) ; Water quality (k)]

Green Water Blue Water Virtual Water

  Î ^DD ÊNV ⁽ ¹ ÎR ⁾ ^DD ^VW

EWR GW

FD

i k

ki ki ki

EU ki

ki j

kij ki

ki

i



 





 





 





 



    



 



   





   

Equivalent-water of foodstuffs production

FD : Equivalent Water Demand for Food

GW

_i

: Equivalent-Water of rainfed agricultural production « Green Water » EWR

_k_i

: Exploitable Water Resources (EWR) « Blue Water »

DD

_k_i

: Direct Water Demand (collectivities, tourism, industry) ; RI

_k_i

: Rate of Water Recycling

: Irrigation Factors for fresh and recycled agriculture water use VW : Equivalent-Water deficit « Virtual Water »

ENV

_k_i

: Environmental Water demand

EUki

ki 



I

_ij

is the volume transferred from region (j) to region (i) that verifies :

so that: I 0

i j

ij





0 I

et I

I

_ij

 

_ji _ii



(38)

Conclusions

The Tunisian case study illustrates how:



“blue water”, “green water”, and “virtual water” are interlinked and constitute the entirety of the water cycle at a national scale



this general analysis acquires a particular and timely relevance in countries that have limited water resources and that have

mobilized a large share of their resources.

This aspect of the issue should



call into question certain established concepts, such as the definition of water resources, water stress, water policies, integrated water resource management, and demand

management,



require more investigations in order to precise the different

elements of the global water resource balance particularly the

accurate assessment of green water potential

(39)

Green Water Blue Water Virtual Water

  Î ^DD ÊNV ⁽ ¹ ÎR ⁾ ^DD ^VW

EWR GW

FD

i k

ki ki ki

EU ki

ki j

kij ki

ki

i



 





 





 





 



    



 



   





   

Equivalent-water of foodstuffs production

GW

_i

: Equivalent-Water of rainfed agriculture « Green Water »

To be evaluated according the cultivated aeras and rainfall in region (i)

i i i

ev

i

k P S

GW 

For olive trees in the region of Sfax

64 , 0

k

_ev

 But the transformation of rainfall- green Water is not necessary linear ?

Ongoing research : Green Water assessment

Rainfall variablity – climate change impacts ?

(40)

Passer à la

Ongoing research : Green Water assessment

Rainfall variablity – climate change impacts ?

But the transformation of rainfall-green Water is not necessary linear ?

? S ) h ( P ) h ( k )

h (

GW 

_EV

For a given hydrologic condition (h)



 k ( h ) P ( h ) Sf ( h ) dh

GW

_EV

where f(h) is the pdf of the hydrologic condition (h)

1990 1991

1992 1993

1994 1995

1996 1997

1998 1999

2000 2001

2002 2003

2004

Cereales Pluie mm

0 100 200 300 400 500 600 700 800mm

a global assessment of water

Water scarcity and food security : a global assessment of water

potentiality in Tunisia

Jamel Chahed*, Mustapha Besbes*, Abdelkader Hamdane**

4º Marcelino Botin Water Workshop,

Santander, September 22-25, 2009

References

Besbes M., Chahed J., Hamdane A. (2007), Bilan intégral des ressources en eau de Tunisie, sécurité hydrique et sécurité alimentaire, Communication at Académie d’Agriculture. Paris, séance du 4-4-2007 (l’Avenir des Eaux

Continentales)

Chahed J., Hamdane A., Besbes M.,(2007), Bilan intégral des ressources en eau de Tunisie, sécurité hydrique et sécurité alimentaire, La Houille

Blanche N°3,2007

Chahed J., Hamdane A., Besbes M.,(2008), A Comprehensive Water

Balance of Tunisia: Blue Water, Green Water, Virtual Water, Water

International, 33:4, pp. 415-424

Pluvial water resources

36000 Mm

225 mm/year Withdrawl water resources

4850 Mm

< 500 m3/cap/year

• Surface water : 2700 Mm

• Ground water : 2150 Mm3 Withdrawal resources

3150 Mm

600 Mm

Reserve for drought

+120 Mm

EUT (Treated Waste Water)

Tunisian water resources

Surface water Ground Water

Water uses

• is limited

~ 500 m

/Cap/year

• is non uniformly distributed - In space

- In time

• is largely exploited (~ 80 %)

Water resource

Water uses

Tunisian water resources : Transfers and Water uses

Drinking Water: 300 Mm

≈ (30 m

/Cap/year) Industrial Water: 100 Mm

≈ (10 m

/Cap/year) Tourist Water : 20 Mm

≈ (2 m

/Cap/year)

Agriculture : 2100 Mm

≈ (210 m

/Cap/year)

DIRECTLY USED

1620 Mm3 (180 m3/ hab /an)

UNUSED

955 Mm3

470

WATER RESERVE 470 Mm3

Evaporation in dams [ 80] Allocated and unused [ 170]

Allocations PPI non utilisées [ 240]

Network losses Sonede [ 85]

Aquifer recharge [ 1%]

1620

955

70

WITHDRAWN WATER

3115 Mm3 (346 m3/ hab year)

Statement 1: Irrigation consumes a large part of water resources

Direct water uses

(collectivities, tourism,

industry) represent less than 20 % of water uses.

Agriculture water uses

represent more than 80 % of water uses.

Irrigation occupies less than

1/10 of cultivated areas and

produces around 1/3 of food

production

Statement 2: «Blue Water» supply is stabilized and agricultural water allocations will be

reduced

Evolution of water resource estimation 10

m

Statement 3: Equivalent-Water of foodstuffs imports is important

Foodstuffs imports-export, 10

m

Jamel Chahed, Mustapha Besbes, Abdelkader Hamdane**

Foodstuffs exports, Equivalent-Water [10 ⁶ m ³ /year]