07. chahed besbes-hamdane_water_scarcity_and_food_security-_water_potential_in_tunisia
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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
4º Marcelino Botin Water Workshop,
Santander, September 22-25, 2009
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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
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Pluvial water resources
36000 Mm3 225 mm/year
Withdrawl water resources
4850 Mm3 < 500 m3/cap/year
• Surface water : 2700 Mm3
• Ground water : 2150 Mm3
Withdrawal resources
3150 Mm3
600 Mm3 Reserve for drought
+120 Mm3 EUT (Treated Waste Water)
Average rainfall
Tunisian water resources
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première pageSource: L.Frigui & Annuaire Hydrologique, DGRE, TunisSurface water Ground Water
éch:
500 M m3/an
éch:
500 M m3/an
Données DGRE
L.Frigui & Annuaire Hydrologique, DGRE,
Data DGRE
es DGREDonnééch:
360 M m3/an
Water uses
Source: DGGR,DGRE
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• is limited
~ 500 m3/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 Mm3 ≈ (30 m3/Cap/year)
Industrial Water: 100 Mm3 ≈ (10 m3/Cap/year)
Tourist Water : 20 Mm3 ≈ (2 m3/Cap/year)
Agriculture : 2100 Mm3 ≈ (210 m3/Cap/year)
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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
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Statement 2: «Blue Water» supply is stabilized and agricultural water allocations will be reduced
Evolution of water resource estimation 106m3
19681972
19801985
19901996
2005
Ground Water
Surface Water 0
500
1000
1500
2000
2500
3000
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Statement 3: Equivalent-Water of foodstuffs imports is important
Foodstuffs imports-export, 106m3/year, average 1990-2004
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Exportations
Importations
Production0
2000
4000
6000
8000
10000
12000
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Statement 4: The amount of «Green Water» is considerable
Equivalent eau; Mm3/an; Moyenne 1990-2004Import 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
Su c r e , c a f é , t h é
5 %
Huiles
17%
Fruits
11%
Market-
gardening; 1305
OliveOil
1555
Dats; 700
Citrus Fruits 220
Other fruits 755
Cereals; 2515
Meat; 1920
Rainfed agriculture
- Cereals, Olive oil…
Irrigated agriculture
(Market gardening, Dats, Fruits…
Equivalent Water of Food production, 106m3/year, 1990-2004
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oil; 1867
Market gardening;
110
Cereals ; 2154
Meat; 1488
Other; 90Sugar , cofee ,
thee; 670
Statement 5: «Green Water» plays un important part in foodstuffs trade
Foodstuffs imports, Equivalent-Water [106m3/year], 1990-2004
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Foodstuffs exports, Equivalent-Water [106m3/year]
Olive oil; 1100
Dates; 200
Citreous Fruits; 25
Drinks; 65
Market-gardening; 90
Other; 80
Cereals; 190
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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.
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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.
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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.
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Foodstuffs exports in value [%]
Sea products20%
dates11%
Citreous fruits2%
Olive oil46%
cereals
7%
Wine and drinks3%
other11%
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Foodstuffs imports in value [%]
Meat 3% Milk
8%
Durum7%
Wheat20%
Barley4%Corn
8%Potato
2%
Oil15%
Thee coffee
6%
Sugar 14%
Other13%
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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
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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)
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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
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Trends in agricultural water use, 1990–2006
467370449825433145417285402200377968353282334700Irrigated area ha
43554575480950585323566660206320Water use allocation m3/ha
20302025202020152010200520001996Year
Eau 21 Projection"Eau 21, Long term water strategy in Tunisia, 2030", Min. Agr., 1998
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Rainfed agricultural evolution, 1960–2007
Wheat cultivated area [ha]
0
200000
400000
600000
800000
1000000
1200000
1400000
19
61
19
62
19
63
19
64
19
65
19
66
19
67
19
68
19
69
19
70
19
71
19
72
19
73
19
74
19
75
19
76
19
77
19
78
19
79
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80
19
81
19
82
19
83
19
84
19
85
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86
19
87
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88
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
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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
19
74
19
75
19
76
19
77
19
78
19
79
19
80
19
81
19
82
19
83
19
84
19
85
19
86
1987
19
88
19
89
19
90
1991
19
92
1993
1994
1995
1996
1997
1998
1999
2000
20
01
20
02
20
03
20
04
20
05
20
06
20
07
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Modeling long term water demand and resourcesTrend 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
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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
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Meet consumption kg/capita/year : (except fish an sea products), 2000
20
90
120
0
20
40
60
80
100
120
Tunisia France USA
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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)
-
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Modeling Food Demand Water Footprint
IW : Irrigation Water VolumeEWR : 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
ENVDD)RI1(EWRIW
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 :
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)ENVDD)RI1(EWR(GWFDVW
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 /FDVW
Green Water Blue WaterVirtual Water
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Model validation 1996-2004VW)ENVDD)RI1(EWR(GWFD
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%
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Modeling long term water demand and resourcesTrend 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)ENVDD)RI1(EWR(GWFD
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Modeling long term water demand and resourcesTrend scenarios (horizon 2050)
Model
Adjustment
2004
Simulation 1 Simulation 2
Population [106 habitants] 9.93 13 13
Exploitable Resource (EWR) [106m3/year] 2500 2700 2700
Food demand, Eq. water [m3/year/Capita] 1450 1700 1800
Total food demand (FD) water[106m3/year] 14399 22100 23400
Direct water demand [m3/year/Capita] 55 70 80
Total direct water demand (DD)[106m3/year] 546 910 1040
Reuse rate, RI 0.1 0,5 0,5
Total irrigation allocation (IW) [106m3/year] 2008 2245 2180
Rainfed agriculture (GW) [106m3/year] 8000 8000 8000
Conversion factor, k 0.9 0,9 0,9
Deficit of food balance (VW) [106m3/year] 4591 12080 13438
Total water demand 14945 23010 24440
Rate of dependency 31% 52% 55%
VW)ENVDD)RI1(EWR(GWFD
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Modeling long term water demand and resourcesSustainable scenario (horizons 2025 -2050)
Model
Adjustment
2004
Sustainable Scenario
2025 2050
Population [106 habitants] 9.93 12,15 13
Exploitable Resource (EWR) [106m3/year] 2500 2700 2700
Food demand, Eq. water [m3/year/Capita] 1450 1700 1800
Total food demand (FD) water[106m3/year] 14399 20655 23400
Direct water demand [m3/year/Capita] 55 70 80
Total direct water demand (DD)[106m3/year] 546 851 1040
Reuse rate, RI 0.1 0,5 0,5
Total irrigation allocation (IW) [106m3/year] 2008 2275 2180
Rainfed agriculture (GW) [106m3/year] 8000 10000 12000
Conversion factor, 0.9 0,9 0,9
Deficit of food balance (VW) [106m3/year] 4591 8608 9438
Total water demand 14945 21506 24440
Rate of dependency 31% 40% 39%
VW)ENVDD)RI1(EWR(GWFD
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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
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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…
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Disparities between the regions
éch:
500 M m3/an
éch:
500 M m3/an
L.Frigui & Annuaire Hydrologique, DGRE, Surface Water Ground Water
Data DGREes DGREDonné
éch:
360 M m3/an
Wtar use
Source: DGGR,DGRE
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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
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Ongoing research: Global Water balance regionalization [Region (i) ; Water quality (k)]
Green Water Blue Water Virtual Water
VWDD)IR1(ENVDDIEWRGWFDi k
kikikiEUkiki
j
kijkikii
Equivalent-water of foodstuffs production
FD : Equivalent Water Demand for Food
GWi : Equivalent-Water of rainfed agricultural production « Green Water »
EWRki : Exploitable Water Resources (EWR) « Blue Water »
DDki : Direct Water Demand (collectivities, tourism, industry) ;
RIki : Rate of Water Recycling
: Irrigation Factors for fresh and recycled agriculture water use
VW : Equivalent-Water deficit « Virtual Water »
ENVki : Environmental Water demand
EUkiki
Iij is the volume transferred from region (j) to region (i) that verifies :
so that: 0Ii j
ij 0IetII iijiij
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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
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Green Water Blue Water Virtual Water
VWDD)IR1(ENVDDIEWRGWFDi k
kikikiEUkiki
j
kijkikii
Equivalent-water of foodstuffs production
GWi : Equivalent-Water of rainfed agriculture « Green Water »
To be evaluated according the cultivated aeras and rainfall in region (i)
iiievi SPkGW
For olive trees in the region of Sfax
64,0kev But the transformation of rainfall-green Water is not necessary linear ?
Ongoing research : Green Water assessment Rainfall variablity – climate change impacts ?
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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)
dh)h(Sf)h(P)h(kGW 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