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 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
|Area of the country||1995||16 361 000||ha|
|Cultivable area||1991||8 700 000||ha|
|Cultivated area||1993||4 254 600||ha|
|- annual crops||1993||2 180 800||ha|
|- permanent crops||1993||2 073 800||ha|
|Total population||1995||8 896 000||inhabitants|
|Water supply coverage:|
TABLE 2 - Water: sources and use
|Renewable water resources:|
|Internal renewable water resources||3.52||km³/yr|
|Total (actual) renewable water resources||1995||4.12||km³/yr|
|Total (actual) renewable water resources per inhabitant||1995||463||m³/yr|
|Total dam capacity||1991||1 510||106 m³|
|- agricultural||1990||2 728||106 m³/yr|
|- domestic||1990||261||106 m³/yr|
|- industrial||1990||86||106 m³/yr|
|Total water withdrawal||3 075||106 m³/yr|
|as % of total (actual! renewable water resources||74.6||%|
|Other water withdrawal||-||106 m³/yr|
|Average groundwater depletion||1990||160||106 m³/yr|
|Wastewater - Non-conventional water sources:|
|- produced wastewater||-||106 m³/yr|
|- treated wastewater||1993||96||106 m³/yr|
|- reused treated wastewater||1993||20||106 m³/yr|
|Desalinated water||1990||83||106 m³/yr|
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:
TABLE 3 - Irrigation and drainage
|Irrigation potential||1991||563 000||ha|
|1. Full or partial control irrigation: equipped area||1991||355 000||ha|
|- surface irrigation||1991||294 000||ha|
|- sprinkler irrigation||1991||55 000||ha|
|- micro-irrigation||1991||6 000||ha|
|% of area irrigated from groundwater||1991||60.7||%|
|% of area irrigated from surface water||1991||37.3||%|
|% of area irrigated from non-conventional sources||1991||2.0||%|
|% of equipped area actually irrigated||1991||90.7||%|
|2. Spate irrigation area||1991||30 000||ha|
|3. Equipped wetland and inland valley bottoms (i.v.b.)||-||ha|
|Total irrigation (1 +2+3)||1991||385 000||ha|
|- as % of cultivated area||9||%|
|4. Flood recession cropping area||-||ha|
|Total water managed area (1 +2+3+4)||1991||385 000||ha|
|- as % of cultivated area||9||%|
|- increase over last 10 years||-||%|
|- power irrigated area as % of water managed area||1991||67.5||%|
|Full or partial control irrigation schemes: Criteria|
|Large-scale schemes > - ha||-||ha|
|Small-scale schemes < - ha||-||ha|
|Total number of households in irrigation||1991||141 000|
|Total irrigated grain production||1991||82 500||tons|
|as % of total grain production||1991||4||%|
|Harvested crops under irrigation (full or partial control}||1992||308 000||ha|
|- permanent crops: total||1992||130 000||ha|
|- annual crops: total||1942||178 000||ha|
|. vegetables||19:32||108 000||ha|
|. wheat||1992||33 000||ha|
|. other annual crops||1992||37 000||ha|
|Drainage - Environment.|
|Drained area||1991||162 000||ha|
|as % of cultivated area||4||%|
|- drained areas in full or partial control irrigated areas||1991||162 000||ha|
|- drained areas in equipped wetland and i.v.b||-||ha|
|- other drained areas||-||ha|
|- total drained area with subsurface drains||1991||162 000||ha|
|- total drained area with surface drains||-||ha|
|Area salinized by irrigation||-||ha|
|Population affected by water-borne diseases||-||inhabitants|
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.
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):
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)
The Ministry of Agriculture is the main institution involved in the water sector. The main General Directorates in charge of water are:
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.