Tunisia

GEOGRAPHY AND POPULATION

Tunisia, situated in the north of Africa, has a total area of 193 610 km², of which 11 160 km², almost 7%, consist of lakes and shats (salty depressions). It is bordered in the north and northeast by the Mediterranean Sea, in the south-east by Libya and in the south and west by Algeria.

The country can be divided into four physiographic regions:

• The North-western Mountains, which are located at the eastern end of the two mountain ranges, the Atlas El-Talli and the Desert Atlas, which extend from Morocco through Algeria and reach a peak at 1 500 metres in Tunisia. This area is crossed by permanent rivers;
• The Southern Mountains, which slope towards the east to the Coastal Plains and towards the west to the Desert Plains and are covered by sand dunes;
• The Coastal Plains which run close to the Mediterranean Sea as wide plains;
• Desert Plain. This plain forms the northern boundary of the Great Desert (Sahara). A number of shats exist in this plain, the largest one being the Shat El-Jarid with an area of 5 000 km² at a minimum elevation of 15 metres below sea level.

The cultivable area is estimated at 8.7 million ha, which is about half the total area of the country. In 1993, the cultivated area was estimated at 4.25 million ha, of which 2.18 million ha consisted of annual crops and 2.07 million ha of permanent crops.

The total population is 8.9 million (1995) and 43% is rural as against 60% 25 years ago. The annual demographic growth rate is less than 2%. Most of the towns and the people are in the northern and central coastal zones. The rural population lives mainly in 4 500 villages. Agriculture employed 30% of the labour force in 1993. There are about 380 000 farm holdings, with an average area of 14 ha. During the period 1989-93 GDP increased about 5% per year. The importance of the agricultural sector in the economy decreased from 1960 to 1994: in 1960 it accounted for 24% of the country's GDP, while in 1994 this figure had fallen to 16%.

TABLE 1 - Basic statistics and population

TABLE 2 - Water: sources and use

Water resources

The hydrographic system is dense in the north where the Medjerda wadi is the most important water course. This is also the zone where the principal irrigation development and flood protection works have been carried out.

Surface water resources have been estimated at 2.91 km³/year, of which 2.31 km³ are produced internally. About 1.5 km³/year are exploitable at present through reservoirs. It will be possible in the future to exploit another 0.6 km /year, but the remaining part could only be used by means of large water conservation works and groundwater recharge systems. At present, there are 18 large dams and 22 hillside dams.

Internal renewable groundwater resources have been estimated at 1.21 km³/year. At present, there are 83 000 open wells and 1 830 tubewells. Two categories of groundwater resources can be distinguished in function of the depth:

• when the water table is above 50 metres, groundwater is defined as phreatic and can be used for private exploitation (with some restrictions). The potential has been estimated at 669 million m³/year;
• below 50 metres of depth, the groundwater has been reserved for public exploitation. Potential has been estimated at 1 170 million m³/year, of which 630 million m³ is fossil water.

TABLE 3 - Irrigation and drainage

Wastewater

For the last 20 years, reuse of treated wastewater has taken place. In 1993, 96 million m³ was treated, of which 20 million m³ was reused. It is planned to increase the treatment to 200 million m³/year by the year 2000.

Water withdrawal

In 1990, water withdrawal was estimated at about 3.1 km³/year, of which almost 89% for agricultural purposes (Figure 1). However, the amount of water withdrawn depends to a large extent on the quantity and the distribution of the precipitation. In particular, irrigation water withdrawal varies in function of the rainfall and of the area actually irrigated within the public irrigation network. Of the total of 3.1 km³ of water used annually, only 1.9 km³ are estimated to be actually used.

In 1992, the rural population with access to good drinking water within a distance of 3 km was estimated at 65 %, while 91 % of the urban population was connected to the drinking water supply network.

Figure 1 - Water withdrawal (total: 3.1 km³ in 1990)

Figure 2 - Distribution of the water managed areas (total: 385 000 ha in 1991)

Figure 3 - Kind of irrigation in the f/p control schemes (total: 355 000 ha in 1991)

IRRIGATION AND DRAINAGE DEVELOPMENT

The irrigation potential has been estimated at 563 000 ha, based on land and water resources. This area can be divided in to 402 000 ha with possibilities for full or partial control irrigation development and 161 000 ha of spate irrigation.

In 1991, the water managed area was estimated at 385 000 ha, including 355 000 ha of full or partial control irrigation schemes and 30 000 ha of spate irrigation (Figure 2). The average annual growth of irrigation development is about 2 %, which means that at this rate full potential will have been achieved by the year 2010.

The area equipped for full or partial control irrigation can be divided into 52 000 ha of complementary irrigation and 303 000 ha of socalled intensive irrigation (Figure 3). Surface irrigation techniques are mainly practiced on the schemes with complementary irrigation and some sprinkler irrigation is used on cereals in case of a severe rainfall deficit and on fruit trees during the early years of their development. The intensive irrigation schemes can be divided into (Figure 4):

• 140 000 ha of small schemes developed individually by the farmers (70 000 households) through private investments and irrigated by open wells or by pumping of water in the wadis;
• 163 000 ha of schemes with a communal irrigation network, irrigated by tubewells in the case of medium schemes (60 000 ha; 47 000 households) and by dams in the case of large schemes (103 000 ha; 24 000 households). These schemes have been developed with public investment.

Figure 4 - Typology of the f/p control intensive irrigation schemes (total: 303 000 ha in 1991)

Figure 5 - Water distribution systems in the f/p control intensive irrigation schemes (total: 303 000 ha in 1991)

Figure 6 - Irrigation techniques in the f/p control intensive irrigation schemes (total: 303 000 ha in 1991)

Figure 7 - Origin of irrigation water in the f/p control intensive irrigation schemes (total: 303 000 ha in 1991)

The communal irrigation water distribution systems are in general modern. There are prefabricated canals or low pressure pipes for surface irrigation and high pressure pipes for sprinkler irrigation (Figure 5). Surface irrigation remains the most important irrigation technique (Figure 6). At present, about 6 000 ha are irrigated by treated wastewater, the remaining part by surface water (dams, pumping in wadis) and by groundwater (open wells, tube-wells) (Figure 7).

The evolution of the area equipped for full or partial control intensive irrigation is shown in Figure 8. In 1991, the actually irrigated area was 270 000 ha, which is about 89% of the equipped intensive irrigation area.

Fruit trees (dates, oranges, grapes, etc.) and vegetables (tomatoes, melons, water melons, potatoes, etc.) are cultivated on about 70% of the full or partial control schemes actually irrigated. However, recent government encouragement for the development of dairy livestock has led to an increase in the irrigation of cereals and fodder crops. The irrigation sector contributes about 3035% to the agricultural value of the country. In 1992, about 308 000 ha were actually irrigated and harvested, which is 80% of the water managed area of 385 000 ha (Figure 9).

The cost of irrigation development for the public schemes varies between $US 6 000 and 7 000/ha depending on the size of the scheme. The annual operation and maintenance costs are about $US 130/ha, of which 25-30 % is spent on energy.

Large-scale public irrigation schemes are managed by the state while medium-scale public irrigation schemes are managed by users associations (AIC or Associations d'intérêt collectif). The services of the state or AIC are in charge of the operation and maintenance of the irrigation network as well as of the distribution of water to the farmers, applying a water charge according to volume. However irrigation water is still subsidized by the state for up to 20-30% of its real exploitation cost.

Irrigation water is quite saline (1.5-4.0 g/l), but the degree of salinization of the irrigated soils is not yet a serious problem due to the low intensification. A monitoring system has been set up for all the schemes with a high risk of salinization. Subsurface drainage is not very developed (162 000 ha) and is limited to soils with a high water table (schemes in the north).

Figure 8 - Evolution of the area equipped for 'intensive' irrigation

Figure 9 - Irrigated crops (total: 308 000 ha in 1992)

INSTITUTIONAL ENVIRONMENT

The Ministry of Agriculture is the main institution involved in the water sector. The main General Directorates in charge of water are:

• The General Directorate of Water Resources (DGRE or Direction générale des ressources en eau), which is in charge of the monitoring and evaluation of water resources;
• The General Directorate of Large Hydraulic Works (DGGTH or Direction générale des grands travaux hydrauliques), the main activity of which is the construction of dams;
• The General Directorate of Hydraulic Studies and Works (DGETH or Direction générale des etudes et travaux hydrauliques), the main activities of which are: general hydraulics studies, construction of hillside dams, development of large-scale schemes and management of the dams;
• The General Directorate of Rural Engineering (DGGR or Direction générale du genie rural), which is responsible for irrigation, rural equipment and for drinking water supply to the rural population.

The regional agricultural development offices (CDRA or Cornmissariat regional de développement agricole), linked to the Ministry of Agriculture, are the institutions responsible at regional level for the development of public irrigation schemes. The management of these schemes is shared between CDRA and AIC.

The water code, promulgated in 1975, determines all interventions in the water sector.

TRENDS IN WATER RESOURCES MANAGEMENT

The strategy for the future use of water, adopted in 1990, aims at the development of 90% of surface water resources and 100% of groundwater resources by the year 2010, by means of the construction of 21 dams, 235 hillside dams and 610 deep tube-wells.

This improvement in the control of water resources is associated with the agricultural development of the irrigation schemes. The objectives of the country are at present to encourage the adoption of water saving techniques, to favour the reuse of treated wastewater for irrigation, to expand the irrigated areas and to set up the related activities necessary for agricultural development and a better use of irrigation schemes.

MAIN SOURCES OF INFORMATION

Agrar, Coyne and Bellier, GKW, Ministère de ['agriculture. 1992. Economie d'eau 2000.

Direction générale des ressources en eau, Ministère de ['agriculture. 1991. Commission de réflexion sur le développement des ressources en eau de surface.

Direction générale du genie rural, Ministère de ['agriculture. 1992. Rapport du Comité Irrigation. - Vlll Plan.

Direction générale du genie rural, Ministère de ['agriculture. 1994. La gestion de l'eau en Tunisie.

Direction générale du genie rural, Ministère de ['agriculture. 1994. Tarification de l'eau d'irrigation 1992 et 1993.

GERSAR and SOTUETEC. 1987. Gestion et entretien des périmètres irrigués.

Hamza, M. and Khanfir, R. 1992. Evolution du potentiel et de ['exploitation des ressources en eau souterraines.

Ministère de ['agriculture. 1992. Annuaire des statistiques agricoles.

Ministère de ['agriculture. 1993. Résultats de l'enquête-suivi de la campagne agricole 1992/93.

Ministère de l'environnement et de l'aménagement du territoire. 1992. Rapport national de la CNUCED.

Office national de l'assainissement. 1994. Rapport d'activités 1993.