Estimation of the economic loss due to irrigation water use inefficiency in Tunisia

Abstract

The main objective of this study is to estimate the total economic loss due to inefficient use of irrigation water in Tunisia. Several approaches have been used for this purpose. The optimal level of water application for different crops is calculated using the actual crop evapotranspiration which is based on FAO-56 method. The residual imputation and yield comparison methods have been used to estimate the economic value of irrigation water for different irrigated crops in different bioclimatic areas. For the empirical analysis, primary data were obtained from a series of surveys that covered 78% of the total irrigated areas and were collected within the framework of the “Virtual Water and Food Security in Tunisia project” (2013–2015). Secondary data about land distribution of crops in Tunisia were taken from the Ministry of Agriculture (2016). Around 724 farms were randomly sampled considering their bioclimatic area, farm type, and production system. The survey included the main 20 crops produced in Tunisia. Results show that most of farmers are either under or over utilizing irrigation water. The value of total direct economic losses, at the country level, of both types of water inefficiencies, was estimated to around 470 million Tunisian Dinars. Therefore, an improvement of water use efficiency at field level through dissemination of information/knowledge on irrigation scheduling and crop water requirements by extension services to farmers is needed to reduce this huge economic loss, reach higher sustainability in water use and improve food security.

Full text

RESEARCH ARTICLE
Estimation of the economic loss due to irrigation water use
inefficiency in Tunisia
Ali Chebil
1
&Asma Souissi
2
&Aymen Frija
3
&Talel Stambouli
4
Received: 8 October 2018 /Accepted: 13 February 2019
#Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract
The main objective of this study is to estimate the total economic loss due to inefficient use of irrigation water in Tunisia. Several
approaches have been used for this purpose. The optimal level of water application for different crops is calculated using the
actual crop evapotranspiration which is based on FAO-56 method. The residual imputation and yield comparison methods have
been used to estimate the economic value of irrigation water for different irrigated crops in different bioclimatic areas. For the
empirical analysis, primary data were obtained from a series of surveys that covered 78% of the total irrigated areas and were
collected within the framework of the BVirtual Water and Food Security in Tunisia project^(2013–2015). Secondary data about
land distribution of crops in Tunisia were taken from the Ministry of Agriculture (2016). Around 724 farms were randomly
sampled considering their bioclimatic area, farm type, and production system. The survey includedthe main 20 crops produced in
Tunisia. Results show that most of farmers are either under or over utilizing irrigation water. The value of total direct economic
losses, at the country level, of both types ofwater inefficiencies, was estimated to around 470 million Tunisian Dinars. Therefore,
an improvement of water use efficiency at field level through dissemination of information/knowledge on irrigation scheduling
and crop water requirements by extension services to farmers is needed to reduce this huge economic loss, reach higher
sustainability in water use and improve food security.
Keywords Water losses .Under and over-irrigation .Irrigation crop’srequirement .Economic water value .Residual and yield
comparison methods .Irrigated sector .Farms .Tunisia
Introduction
Water resources in Tunisia are very limited. The per capita
water availability is around 400 m
3
per year, which is by far
lower than the penury threshold of 1000 m
3
. This value is
expected to decrease to 350 m
3
in 2030 (IETS 2018). Tunisia
is influenced by the arid and semi-arid climate which covers
more than 75% of its area with limited and variable rainfall.
The agricultural sector is highly dependent on water re-
sources since it accounts for 80% of the total water use in the
country. Irrigation is a key component of agricultural produc-
tion in Tunisia, covering about 450 thousand hectares (MA
2016). Currently, the irrigated areas represent 8% of the total
agricultural areas, contributing to 35% of the total agricultural
production and 20% of the agricultural exports (Dhehibi et al.
2014). Furthermore, the growth of agricultural production in
Tunisia is mainly due to the expansion of irrigated areas. In
fact, for decades, significant efforts to mobilize water resources
have been made by the government. Thus, water supply has
almost reached its limit. Imbalance between water supply and
demand is expected to have a critical effect on irrigated agri-
culture in the coming years. In these circumstances, the oppor-
tunity cost of water will increase, with the sustainability of the
irrigation activity being threatened. The current growth of ag-
ricultural water demand is also faced with a hard competition
Responsible editor: Philippe Garrigues
*Ali Chebil
chebila@yahoo.es
1
University of Carthage, National Research Institute for Rural
Engineering, Water and Forestry (INRGREF), Rue Hédi Karray,
B.P.10, 2080 Ariana, Tunisia
2
Institut Supérieur Agronomique (ISA) Chott-Mériem, B.P.47, 4042,
Chott-Mériem, Sousse, Tunisia
3
International Center for Agricultural Research in the Dry Area
(ICARDA), Rue Hédi Karray, Ariana, Tunisia
4
EcoleSupérieured’Agriculture de Mograne (ESA Mograne),
121 Zaghouan, Tunisia
Environmental Science and Pollution Research
https://doi.org/10.1007/s11356-019-04566-8

from urban and industrial sectors. The pressures on water re-
sources have been increased and the degradation of water re-
sources is threatening human water security, food security, and
environmental biodiversity in Tunisia.
Thus, a sustainable development of agriculture in Tunisia can
onlybe possible throughrationalizing the irrigationwater demand
andimproving theefficiency ofits use startingfrom thefield level.
Indeed,the gaps betweenthe potentialand actual yieldsat the field
level amount to 50–60%, depending on the crops (Zairi et al.
2003). Also, several recent economic studies concerning the irri-
gation water use efficiency (IWUE) at the farm level show that a
large potential for improvement of the IWUE exists in Tunisia
(Dhehibi et al. 2007;Frijaetal.2009;Chemaketal.2010; Chebil
et al. 2012; Chebil and Frija 2016). In general, water policy and
poor irrigation management in Tunisia conducted to important
losses of water value because most of farmers are applying either
higher (overuse) or lower (underuse) volumes compared to the
optimum dose. Overuse of water leads to waste and further deg-
radation of water resources while underuse of water means that
farmers can improve their yield through further supplementary
irrigation. To our knowledge, no study has been conducted to
assess the overall loss of economic value in irrigation sector at
national levels. The main objectives of this study are to estimate
theaggregate lossof economic valueassociated with bothtypes of
water inefficiencies for different irrigated crops in the different
bioclimatic areas of Tunisia and to provide recommendations on
how to reduce these economic losses and improve water use effi-
ciency at field level.
Water resources and irrigated agriculture
in Tunisia
Water demand in Tunisia
The rainfall pattern in Tunisia is irregular in space and time.
The average annual rainfall is 230 mm. It is around 594 mm in
the north, 289 mm in the center, and 156 mm in the south; it
varies between a maximum of 1500 mm in the northwest and
a minimum of 50 mmin the south. Furthermore, the rainfall is
concentrated in the winter period.
The total potential of water resources in the country is
about 4.8 billion m
3
of which 2.7 billion m
3
is derived from
surface water and 2.1 billion m
3
from groundwater (Table 1).
Water resources are unevenly distributed across the country
with around 60% located in the north, 18% in the center, and
22% in the south. Surface water is mobilized through large
infrastructure, mainly 27 large dams, 182 hills dams, and 698
artificial lakes. Groundwater resources account for around
43% of the total water potential. They are confined within
212 shallow aquifers and 267 deep aquifers (MA 2016).
Shallow aquifers in Tunisia were submitted to an increas-
ing pressure during the last two decades. This pressure was
particularly higher in coastal and central regions. They have
been the main irrigation source for the private irrigated areas
of Tunisia, which cover around 38% of the total irrigated areas
in the country. Private irrigated areas are those areas which are
irrigated fromwells. Moreover, deep aquifers are also used for
the irrigation of some public irrigated areas mainly in the
southern oases. With the expansion of irrigated areas, the pres-
sure on groundwater resource was quickly multiplied. In fact,
the number of wells in Tunisia increased from 60,415 in 1980
to 151,850 in 2015 (DGRE 2017). Many of the private irri-
gated areas experienced critical situations due to the overex-
ploitation of groundwater. Soils salinization in many of these
areas, irrigated from low-quality groundwater, is an illustra-
tion of degradation.
The non-conventional water resources (reclaimed waste-
water and desalinated water) represent only 5% of the total
available resources. Out of the 250 million m
3
of wastewater,
only 120 million m
3
is treated in 52 treatment plants.
Desalinization of brackish groundwater using reserve osmosis
is under development and in operation essentially in the center
and south of the country. About 7 million m
3
of desalinized
water is currently produced every year. The desalination of
seawater offers a long-term alternative source of drinking wa-
ter which could contribute with up to 50 Mm
3
in 2030 (IETS
2014). The government plans considerable efforts to increase
non-conventional water resources, particularly desalinized
and treated water, in the coming years.
Total water demand in Tunisia is expected to increase from
1870 Mm
3
to 2770 Mm
3
, respectively from 1990 to 2030,
representing an increasing rate of 48% (Table 2). This increas-
ingdemandisexpectedtobemainlyduetothefastgrowthof
Table 1 Water resources in Tunisia (million m
3
)
Potential Accessible Mobilized
1990 2000 2010 2015
Surface water 2700 2500 1179 1876 2200 2500
Groundwater 2140 2140 1576 1818 1900 1940
Total 4840 4640 2755 3694 4300 4440
Mobilizationrate(%) 60809396
Source: ITES 2018
Table 2 Evolution of water demand by sector in Tunisia (million m
3
)
Sectors 1990 2010 2020 2030
Agriculture 1575 2141 2083 2035
Urban 185 361 438 491
Industry 89 136 164 203
Tourism 18313641
Total 1867 2669 2721 2770
Source: IETS 2018
Environ Sci Pollut Res

water demand by the agricultural sector (about 80% of total
water consumption) in addition to improvements in house-
hold’s income and living standards and the development of
the touristic sector. Water use for domestic and touristic sec-
tors has doubled during the past two decades.
Characteristics of the irrigation sector
Irrigated areas have continued to increase in Tunisia during
the past two decades (Table 3). In 2015, they accounted for
around 450,470 ha, of which 49.6% were in the north, 34.7%
in the center, and 15.6% in the center-east of the south (MA
2016). Despite this increase in irrigated areas, the intensifica-
tion and occupation rates
1
have been maintained practically
stable. The intensification rate was approximately 90% in
2015 which is lower than the expected standard of 100% (Al
Atiri 2007). .
The irrigated sector is crucial for the overall economic de-
velopment. It occupies 8% of the country’susefulagricultural
area but contributes significantly to the development of agri-
culture. It accounts for 30–35% of agricultural production
value, 95% of horticultural crops, 30% of dairy production,
70% of tree crop production, 22% of agricultural exports
(mainly oranges and dates), and 26% of total agricultural em-
ployment (Dhehibi et al. 2014).
The irrigated sector will inevitably face a more acute com-
petitive situation in the coming years, because of limited water
resources and the increasing demand from the domestic, tour-
istic, and industrial sectors. Tunisia invested heavily in water
resources mobilization in order to meet the increased demand.
The government made water available at low cost to farmers
through financing major hydraulic public investments. These
solutions are not sustainable given the increasing investment
costs on one hand and the low-cost recovery on the other hand
(Thabet and Chebil 2006).
Three regimes of irrigation management can be identi-
fied in Tunisia, depending on the type of the irrigated
areas. These are the private regime secured by individual
farmers irrigating from their own wells, the public regime
operated by the CRDA (Commisariats Régionales de
Développement Agricole) and the collective regime oper-
ated by the Water User’s Associations (WUAs). In 2015,
private management covered around 47% of the total irri-
gated area. It mainly relates to the areas irrigated from
superficial aquifers. Farmers in these areas are responsible
for the investment and operational costs of their individ-
ual water systems. Collective management concerns areas
that are managed by WUAs. These areas have expanded
to cover 43% of the total irrigated land area in Tunisia in
2015. Collective irrigation networks are set up through
public funds, but their management is delegated to the
WUA, which fixes water fees and would be responsible
for fees collection. Public management of large irrigated
farms is covering around 10% of the total irrigated lands
in Tunisia.
In 2015, the volume of water used for irrigation was esti-
mated to be around 1889 10
6
m
3
, with an average consumption
per hectare of approximately 5000 m
3
/year. Water from shal-
low aquifers irrigates over 150,000 ha, while deep groundwa-
ter irrigates around 70,000 ha. Surface water (mainly from
dams) irrigates 130,000 ha, treated wastewater irrigates
7000 ha, and the rest is partly irrigated from direct pumping
from natural storage (MA 2016).
Conceptual framework: losses of water value
Based on the marginal productivity theory, marginal physical
product curve can be considered as the demand curve for a
given resource. Figure 1illustrates the marginal value of irri-
gation water at a given level of water use. Marginal value of
water decrease as water is applied. The area under the curve
from the origin to the level ofuse of water gives the total value
of the use of that amount of water. The optimum level of water
use corresponds to the level of crop irrigation requirements.
This level is given by W
*
in Fig. 1. In a context of poor
irrigationknowledge and skills, most of the farmers will apply
either lower or higher volumes compared to the optimum
dose. In the case of overuse, the loss associated with non-
Table 3 Evolution of the irrigated
areas (1000 ha) Year Irrigableareas Irrigated areas Effectively irrigated areas Occupationrate Intensification rate
1990 288 188 255 81 89
1995 361.3 288 314.8 80 87
2000 377.3 317.6 345.9 80 92
2005 418.8 326.9 355.2 79 85
2010 457.6 391 437 86 95
2015 496.1 406.6 454.4 80 91
Source: MA 2018
1
Occupation rate = irrigated area irrigable area; Intensification
rate = effectively irrigated areas irrigable areas
Environ Sci Pollut Res

optimal use of water is given by the shaded area between
water level W
2
and W*. In the case of Bunderuse,^the loss
associatedwith non-optimal use of water is given by the shad-
ed area between W* and water level W
1
.
In this study, we considered water requirements to
achieve yields close to the maximum as optimum. The rule
for optimal use of water is to apply water to the level where
the marginal value of the last unit applied equals the price
of water. Regarding the low level of water price (irrigation
water is heavily subsidized by the Tunisian Government)
and for some crops like cereals quite free in Tunisia, the
economic optimum level of water near the water applied at
the level of marginal value of water is around zero. In the
next methodology section, we will provide a methodolog-
ical approach which allows quantifying the total loss of
water value due to overuse and underuse.
Data collection and methodology
Calculation of irrigation crop’srequirement
Calculations of VW amount used by some strategic crops in
Tunisia, which is the actual crop evapotranspiration, are based
onFAO56method(Allan1998), as follows:
ETAi¼P«iþIiþSi−1−Siif P«iþIiþSi−1−Si<ETMi
ETMiif P«iþIiþSi−1−Si≥ETMi
ð1Þ
Since the rainfall water is not totally used by crops, P^
ui
refers to the effective rainfall which is assumed to be equal
to 80% of the total rainfall (green water), and ETM
i
denoted
the monthly maximum evapotranspiration or the crop water
requirements (CWRi). The CWR is calculated from multiply-
ing the potential crop evapotranspiration ET
p
by the crop co-
efficient Kc
i
.I
i
is the monthly amount of irrigationwater given
to the crop (blue water), inthe case of a rainfed crop I
i
=0.S
i−1
and S
i
are the available water in the soil ate month i−1andi,
Marginal water value
(MWV)
MWV
W1W*(optimum) W2Quantity of water (m3/ha)
Source: Own elaboration
Loss of water value associated to under-irrigation
Loss of water value associated to over-irrigatio
n
Fig. 1 Loss associated with non-optimal water use. Source: Own
elaboration
Fig. 2 Irrigation water value of
the different crops studied by
bioclimatic stage (TND/m
3
)
Environ Sci Pollut Res

respectively. The annual ETA is defined then as the sum of the
monthly ETA
i
.
ETA ¼∑ETAið2Þ
The choice of a model depends on the objectives of the
study which is in our case related to the assessment of the
relationship between water and crop production. In such cases,
FAO models (AQUACROP and CROPWAT) are frequently
used. CROPWATis the simplest model and is based on empir-
ical relationships between water availability and production.
Excess is calculated as:
EXCESS ¼ETA þI−ETM ð3Þ
Deficit is calculated as:
DEFICIT ¼ETM−ETA þIðÞ ð4Þ
Estimation of economic water value
Several approaches for estimating water value have been de-
veloped (Young 2005; Calatrava-Leyva and Sayadi 2005;
Mesa-Jurado et al. 2010; Al-Karablieh et al. 2012;Frija
et al. 2014). The residual imputation and yield comparison
methods, which were used by several authors (Louw and
van Schalkwyk 2007;Speelmanetal.2011;Berbeletal.
2011), are also applied in this study.
Return comparison approach
The return comparison approach has been used in the case of
crops which could be cultivated under both rainfed and irri-
gated regimes in the same region. The value of water in agri-
culture can be calculated as follows:
WVi ¼NViI−NViR
Wi ð5Þ
Wate r
value
(The net value of output with irrigation –the net
value of output without irrigation
volume) amount of water applied
WVi The value of water for crop i
NViI The net value of output for crop iunder irrigation
NViR The net value of output for crop iunder rainfed
Wi The amount of water applied
Residual value method
The residualobtained by subtracting the non-water input costs
from total crop revenue can be interpreted as the maximum
amount the farmer who could pay for water and still cover
production costs. In the case of crops cultivated only under
irrigationin the region, the value of water in agriculture can be
calculated as follows:
WVi ¼NViI
Wi ð6Þ
WVi The value of water for crop i
NViI The net value of output for crop i under irrigation
Wi The amount of water applied
Data sources and regions
Data used in this work was collected within the framework of
BVirtual Water and Food Security in Tunisia^EVSAT project
for the years 2013/2015. About 724 farmers were surveyed in
Fig. 3 Shares of the value of
economic losses caused by
irrigation water wastage and by
the irrigation water deficit related
to the studied crops
Environ Sci Pollut Res

the country. The survey included the 24 governorates which
are aggregated into four regions (northwest (NW), central
west (CW), central and southeast (CSE), and southwest
(SW). We considered a stratified random sample of four farm
types in each governorate based on their size (0–5ha;5–20 ha,
20–50 ha, and more than 50 ha). The sample distribution is
determined to take into account the region, the bioclimatic
stage, and the agriculture system (rainfed or irrigated).
Five bioclimatic areas have been also considered: humid
sub-humid (HSH), superior semi-arid (SSA), inferior semi-
arid (HAS), arid (A), and Saharan (S). The survey included
the characterization of the technical and economic aspects
related to the cultivation of the main 20 crops cultivated in
the irrigated areas in Tunisia. It includes a representation of
78% of the total irrigated areas of the country.
Results and discussion
There is great variability in the irrigation water value between
the studied crops and even for the same crop under different
bioclimatic stages. If we consider the irrigation water value of
the different crops studied by bioclimatic stage (Fig. 2), we can
see that in arid regions, crops which have better value irrigation
water are grapes and onion followed by apple, with, respective-
ly, 3.65 TD/m
3
, 2.12 TND/m
3
, and 1.84 TND/m
3
.Intheinfe-
rior semi-arid regions, apple trees, potato, peach trees, and al-
mond have the best irrigation water values with, respectively,
1.71 TND/m
3
, 1.69 TND/m
3
, 1.57 TND/m
3
,and 1.48 TND/m
3
,
respectively. For the superior semi-arid stage, peach trees, cit-
rus, and potato still occupy the first places with, respectively,
2.84 TND/m
3
, 1.99 TND/m
3
, and 1.95 TND/m
3
.Inhumidsub-
humid stage, the highest irrigation water values are 1.53 TND/
m
3
and0.81TND/m
3
for potato and citrus, respectively.
2
Based on the value of irrigation water, we try to empha-
size the importance of optimal and efficient use of water
resources through the evaluation of the economic value of
the Bloss of income^as well as the value of Bwastage of
irrigation water^generated by the inefficiency of the use of
irrigation water in Tunisia mentioned previously by several
authors (Dhehibi et al. 2007;Frijaetal.2009;Chemak
et al. 2010;ChemakandDhehibi2010;Chebiletal.
2013;Dhaouadietal.2017).
Most farmers apply lower and/or higher water volumes
compared to the optimal dose during the different phases of
the crop cycle.
The total direct economic losses related to the consid-
ered crops and evaluated at the national level are estimat-
ed at about 470 million TND at current prices of 2014.
The economic value losses associated with the overuse
and underutilization of irrigation are estimated at 45%
and 55%, respectively. This could be explained by the
high value of arboriculture trees and the area of these
crops which is under supplementary irrigation and having
a strong potential to increase water value.
Figure 3presents shares of losses in economic value at the
national level. Losses due to wastage are highly variable from
one crop to another. They are estimated to be around 92% for
onion, melon, and watermelon productions, 90% for citrus
fruits, 83% for dates, and 82% for tomatoes and 51% for
wheat, while the production shortfall caused by the irrigation
2
The average exchange rate during the survey period is 1.3 Tunisian Dinar
(TND) for $ 1
1000 TND
Fig. 4 Total value of water loss
by crop due to over-irrigation
Environ Sci Pollut Res

water deficit is estimated at almost 100% for the case of olives,
pomegranate, and almond trees and more than 80% for peach
and apple trees and 60% for pepper and potato.
Results also show that the main crops contributing to the
total loss of water value are citrus (with more than 43 million
TND of losses in water value), tomato (with 35million TND),
onion (with 24 million TND), and palm trees (with 20 million
TND) (Fig. 4).
Olive, apple, and potato areas contributed the most to the
total value of income loss, with more than 166 million TND
(almost 80% of the total value of the economic losses is
caused by irrigation deficit), 31 million TND, and 24 million
TND, respectively (Fig. 5).
Results confirm that farmers in Tunisia are not
performing the appropriate water doses and schedule
adapted on their cultivated areas; this may have deep im-
plications in terms of food security and water resources
preservation. Indeed, rational use of irrigation water for
agricultural production is then necessary for yields im-
provement, but also for water resources preservation.
There is a need for changes in water and land allocations
within the agricultural sector and optimal management
practices of irrigation water at the farm level. This may
improve irrigation water use efficiency. Appropriated wa-
ter policies related to water tariffs and crops subsidies are
also required to be implemented by the decision-makers.
Conclusion
The purpose of the paper is to estimate the aggregated loss of
economic value associated with overuse and underuse of irri-
gation water compared to the optimal advised levels in Tunisia.
The results of this study show that most of the farmers are not
performing the appropriate water doses and schedules adapted
to their area. Hence, huge losses of water at a filed level in
irrigated perimeters in Tunisia are observed. The total direct
economic losses, at country level, of both types of water inef-
ficiencies of under and over-irrigation was estimated to around
470 million of Tunisian Dinars at current prices 2014. This
may have deep implications in terms of food security and water
resources preservation. In Tunisia, where more than 75% of its
water resources are allocated to agriculture sector, major efforts
should be done to increase water use efficiency in the field.
Therefore, efficient irrigation is of crucial importance to the
sustainable crop production in the country. This could be
achieved through the efficient use of irrigation systems, dis-
semination of information/knowledge on irrigation scheduling
and crop water requirements by extension services (use of
information communication technology), and the application
of agricultural map. This latter was developed by the Ministry
of Agriculture which recommends the cropping pattern in each
irrigation scheme. Water user’s association can also be used as
a platform for training adhered farmers about advanced irriga-
tion scheduling. Finally, implementation an adequate tariff sys-
tem of water irrigation such as bloc tariff could be considered
as economic tools for water saving.
The results of this study indicate that assessing the aggregate
potential of reducing losses in the economic value of irrigation
water is a useful indicator of sustainable management and se-
curing water for the future in Tunisia. The obtained results help
the scientists to improve their knowledge on methods applied in
this study which could be considered for further studies, the
policy makers to implement the appropriate water policies re-
lated to water tariffs and crops subsidies, and the farming sector
to better water and land allocations. Further research concerning
benefit-cost analysis (comparison of the costs and benefits of
reducing losses) is recommended as perspective work.
1000 TND
Fig. 5 Total value of water loss
by crop due to under-irrigation
Environ Sci Pollut Res

Funding information The authors acknowledge the financial support of
International Development Research Centre (IDRC)for the financial sup-
port during the process of data collection within the framework of the
project BEau virtuelle et sécurité alimentaire en Tunisie (EVSAT)^coor-
dinated by the BEcole Supérieure d’Agriculture de Mograne (ESAM).^
Publisher’snoteSpringer Nature remains neutral with regard to jurisdic-
tional claims in published maps and institutional affiliations.
References
Al Atiri R (2007) Evolution institutionnelle et réglementaire de lagestion
de l’eau en Tunisie. Vers une participation accrue des usagers de
l’eau. In Bouarfa S. et al. (dir.), L’avenir de l’agriculture irriguée
en Méditerranée. Nouveaux arrangements institutionnels pour une
gestion de la demande en eau ». Actes du séminaire Wademed,
novembre 2006, Cahors, France, ClRAD, Montpellier, France, 8 p
Al-Karablieh EK, Salman AZ, Al-Omari AS, Wolff HP, Al-Assa’dTA,
Hunaiti DA, Subah AM (2012) Estimation of the economic value of
irrigation water in Jordan. J Agric Sci Technol 2(B):487–497
Allan JA (1998) Virtual water: a strategic resource. Ground Water 36(4):
545–547
Berbel J, Mesa-Jurado MA, Pistón JM (2011) Value of irrigation water in
Guadalquivir Basin (Spain) by residual value method. Water Resour
Manag 25(6):1565-1579
Calatrava-Leyva J, Sayadi S (2005) Economic valuation of water and
willingness to pay analysis with respect to tropical fruit production
in southeastern Spain. Span J Agric Res 3(1):25–33
Chebil A, Frija A (2016) Impact ofimproving water use efficiency on its
valuation: the case of irrigated wheat production in Tunisia. AfJARE
11(2):131–140
Chebil A, Frija A, Abdelkafi B (2012) Irrigation water use efficiency in
collective irrigated schemes of Tunisia: determinants and potential
irrigation cost reduction. Agric Econ Rev 13(1):39–48
Chebil A, Bahri W, Frija A (2013) Mesure et déterminants de l’efficacité
d’usage de l’eau d’irrigation dans la production du blé dur: Cas de
Chebika (Tunisie). New Medit 12(1):49-55
Chemak F, Dhehibi B (2010) Efficacité technique des exploitations en
irrigué: une approche paramétrique versus non paramétrique. New
Medit 9(2):32-41
Chemak F, Boussemart JP, Jacquet F (2010) Farmingsystem performance
and water use efficiency in the Tunisian semi-arid region: data en-
velopment analysis approach. Int Trans Oper Res 17:381–396
Dhaouadi L, Boughdiri A, Daghari I, Slim S, Ben Maachia S, Mkadmic C
(2017) Localised irrigation performance in a date palm orchard in
the oases of deguache. Journal of New Sciences 42(1):2268-2277
Dhehibi B, Lachaal L, Elloumi M, Messaoud A (2007) Measuring irri-
gation water use efficiency using stochastic production frontier: an
application on citrus producing farms in Tunisia. AfJARE 1(2):99–
114
Dhehibi B, Frija A, Aw-Hassan A (2014) Performances, policies, chal-
lenges and opportunities of the Tunisian agriculture sector from
natural resources management perspective a SWOT analysis. Am
Eurasian J Agric Environ Sci 14:1351–1358
Direction Générale de Ressources en Eau (DGRE) (2017) Stratégie de
mobilisation des ressources en eau en Tunisie. May 2017. Ministère
de l’Agriculture, des Ressources hydrauliques et de la Pêche,
Tunisie
Frija A, Chebil A, Speelman S, Buysse J, Van Huylenbroeck G (2009)
Water use and technical efficiencies in horticultural greenhouses in
Tunisia. Agric Water Manag 96(11):1509–1516
Frija I, Frija A, Chebil A, Cheikh H, Hamed M, Speelman S, Makhlouf M
(2014) Marginal water productivity of irrigated durum wheat in
semi-arid Tunisia. J Agric Sci 6(10):84–95
Institut Tunisienne desEtudesStratégiques (ITES) (2014) Étude
stratégique: Système hydraulique de la Tunisie à l’horizon 2030.
ITES, Tunis
Institut Tunisienne des Etudes Stratégiques (ITES) (2018) Management
of water resources in Tunisia. Bilan and prespective of the future.
ITES, Tunis
Louw DB, Van Schalkwyk HD (2007) The true value of irrigation water
in the Olifants river basin : Western cape. Agrekon 36:551–561
Mesa-Jurado MA, Berbel J, Orgaz F (2010) Estimating marginal value of
water for irrigated olive grove with the production function method.
Span J Agric Res 8(S2):197–206
Ministry of Agriculture (MA) (2016) Survey on irrigated areas, Tunisia
Ministry of Agriculture (MA) (2018) Annual directory of agricultural
statistics. Tunisia
Speelman S, Frija A, Perret S, D'haese M, Farolfi S, D'haese L (2011)
Variability in smallholders' irrigation water values: Study in
NorthWest Province. South Africa Irrig and Drain 60(1):11-19
Thabet C, Chebil A (2006) Irrigation water pricing in Tunisia: issues for
successful water management transparency. Agricultural and
Marine Sciences 11(S.I):21-28
Young RA (2005) Determining the economic value of water: concepts
and methods. Resources for the Future (RFF), Washington, DC 374
pp
Zairi A, El Amami H, Slatni A, Pereira LS, Rodrigues PN, Machado T
(2003) Coping with drought: deficit irrigation strategies for cereals
and field horticultural crops in Central Tunisia. In: Rossi G,
Cancelliere A, Pereira LS, Oweis T, Shatanawi M, Zairi A (eds)
Tools for drought mitigation in Mediterranean Regions. Kluwer,
Dordrecht, pp 181–201
Environ Sci Pollut Res