Agricultural Water Management: Proceedings of a Workshop in Tunisia (2007)

Ameur Horchani

Former Secretary, State of Water Resources,

Ministry of Agriculture, Tunisia

Water resources in Tunisia are characterized by scarcity and a pronounced irregularity. By adopting an integrated strategy for the use of water based on scientific and technical studies, Tunisia has been able to develop a complex and diverse water infrastructure allowing the country to mobilize and exploit available water resources. At the same time, Tunisia has put in place systems and legislation to assure access to drinking water for the majority of the urban and rural population and to provide supplies for agricultural irrigation, as well as the industrial and tourism sectors.

Exploitation of conventional water resources is very advanced and it is expected that water demand, driven by population increases and improvements in living standards could reach its maximum around the year 2030. Aware of this problem, Tunisia has decided to enact a strategy to develop its water resources. This strategy is based on the judicious allocation of a limited and costly resource and the management of the country’s growing demand for water. Effective management of water resources depends on continual monitoring and control as well as the implementation of reforms in the water sector.

These reforms have permitted Tunisia:

• To encourage the valuation of water resources and to fight waste and mismanagement in pricing water for drinking, irrigation systems, and urban demands gradually bringing the price of water closer to its real economic value

• To develop a system for water conservation in the drinking water and irrigated water sectors using technical instruments and financial incentives

• To encourage primary users to form cooperatives that help to control costs and assure greater efficiency in the use of water

Despite the scarcity of water resources, Tunisia has adopted a water policy that has permitted:

• The development of conventional and non-conventional water resources and better control of demand in all socioeconomic sectors based on an integrated and flexible plan

• The development of a system of irrigation zones allowing the country to maintain a stable, growing and sustainable agricultural system

• Minimization of the negative effects of the dry climate on the users

• Assurance of an equitable division of water resources for all regions in Tunisia allowing the majority of inhabitants adequate water resources

Thanks to the use of water policies and innovative reforms in the water sector, Tunisia has been able to assure food security and improve the quality of life in the urban, rural and Saharan zones while satisfying the needs of the industry and tourism sectors and still respecting, as much as

possible, ecosystem limits.

Aware of the problems engendered by charging for water, Tunisia has developed voluntary policies to support the control and the valuing of water resources. Considerable efforts have been deployed to develop all water resources using a variety of means (dams, collinear dams, collinear lakes, emission of sewage waters, desalination, drills, surface wells, treatment of used water, recharging water tables). Several geographic zones are connected by a system of regional canals and locks.

During the last ten years (1990-2000), a strategy was devised and implemented to provide integrated control of potential water sources. The cost of this ten year strategy approached two billion dollars. Modeling has been used to demonstrate the working of several water systems in place. This modeling simulates all possible resources and system demands. The simulation model illustrates potential conflicts caused by the need to satisfy water demands and suggests the appropriate timing of activities to provide additional water resources.

In 2003, Tunisia had 27 dams, 180 collinear dams, 600 collinear lakes, and more than 4000 deep wells and 150,000 surface wells exploiting 86% of total conventional water resources. These proposed projects will permit the development of 90% of conventional water resources by the year 2010. In order to increase the water potential in the country, the use of non-conventional water resources, such as treated waste-water and desalinated briny water, is being encouraged. At the same time, the exploitation of water resources is being managed by better allocating the scarce resource. In addition, the protection of coastal aquifers against the intrusion of salt water is reinforced by regulations.

In summary, the exploitation of conventional water resources in Tunisia is very advanced. It is projected that total water demand, due to population increases and increases in living standards, should reach its limit by the year 2030. Conscious of this problem, Tunisia is engaged in formulating a strategy to more fully develop its water resources and to meet the demands of the various socio-economic sectors. The strategy focuses on demand management and integrated planning systems. The cost of developing additional water sources continues to grow. Management, maintenance and system improvements require substantial investments, effective management and technological improvements. The management and exploitation of hydraulic systems in Tunisia must withstand the scrutiny of users who demand more and better performance at minimum risk. Therefore, public and private management must adapt to the new structures and the users must adjust to the need to make prices reflect new system costs.

Irrigation constitutes the largest consumer of water in Tunisia, using 80% of the total water potential in the country. In 2003, agricultural land accounted for about 370,000 hectares. The phreatic water levels irrigated over 150, 000 hectares, while the deep levels irrigated over 70,000 hectares, for a total of 220,000 hectares. Dams irrigated 130,000 hectares, treated wastewater

served to irrigate 7,000 hectares, and the rest is irrigated partly from pumping directly from temporary water sources and partly from natural sources.

The volume of water used for irrigation is estimated at 2,100 million m³ (cubic meters), with average consumption per hectare of approximately 5500 m³/year. Consumption reaches 20,000 m³/hectare/year in the oasis in the South and is on average about 4000 m³/hectare/year in the North. The amount of irrigated land is expected to reach 400,000 hectares in 2010. Irrigation supports 55% of total agricultural production and 25% of export crops and only represents 7% of usable agricultural lands.

In 2003, 260,000 hectares (70% of the total irrigated land) was equipped with water conservation systems including drip irrigation, sprinklers, pipes and watertight channels. The remaining 100,000 hectares are programmed to be equipped around 2010. A group of collectives (AICs) manage 135,000 hectares of irrigated lands. These associations are responsible for the maintenance of the irrigation network and the distribution of water to their members. Drinking water in metropolitan areas is managed by a national company that distributes 350 million m³ per year to meet the needs of 1.5 million subscribers. The volume is expected to increase to 450 million m³ by 2030. In rural areas, the administration of the drinking water distribution system is handled by cooperative associations (AIC).

Conflicts between various water users will become more acute in the future. There will be pressure on the agricultural irrigation sector to transfer water to the urban, industrial and tourist sectors; the agricultural sector will need to compensate by strengthening water conservation efforts and water efficiency programs. The small traditional farmer will have problems despite government subsidies which may only postpone their economic failure.

Drought is a current and periodic phenomenon in Tunisia, and it is taken into account in all the plans and development programs. Drought can cover one or more regions while being seasonal or annual and it can last two or three successive years. In the last decade, Tunisia has succeeded in overcoming many of the difficulties associated with drought due to strong water management programs, irrigation controls, and a set of effective socio-economic policies.

A practical guide for managing the effects of drought, written in 1999, is based on historic experience in Tunisia as well as on contemporary experiences at the national and international levels. This tool alerts the different institutions concerned with drought to take all necessary precautions and actions to mitigate the effects of drought and to minimize disruptions in the economy. The principal objective of the strategy is to protect vital resources--- water, livestock, orchards, roadways, and forests--- in order to assure drinking water and to support agriculture. Tunisia also experiences exceptional flooding, where water quantities can quadruple. Hydraulic infrastructures limit damage and make use of surpluses. Surpluses are used to refill different water tables.

Since 1960, Tunisia has engaged in studies and demonstration of the re-use of treated wastewater. Currently, 7000 hectares, planted primarily with orchards and for livestock feed, use treated water for irrigation consistent with national law. With expanded urban development and land development, the volume of treated wastewater used is expected to grow to 450 million m³ in 2030, equivalent to 10% of the total conventional resources of the country, permitting the irrigation of 100,000 hectares.

Thus, recourse to treated wastewaters, in areas where demand is highest and quantities are limited, will be encouraged to respond to increasing demand in the irrigation and industrial sectors. In addition, it is important to point out a pilot program to recharge water tables, which is taking place in the Cap Bon region, to assess the usefulness and the acceptance of wastewater extension and use. The use of treated wastewaters from large urban cities like Tunis, Sousse, and Sfax requires large storage capacity and transfer from these centers to areas with resources of lesser quality. The reuse of treated wastewaters in irrigation takes place with strict controls and sanitary procedures consistent with established norms.

Management that integrates groundwater and surface water resources by artificial recharging from surface water resources during surplus periods is an important component of the country’s water management plan. Seventy million m³ were artificially recharged in 1996 and the volume will increase to more than 200 million m³ per year by 2030. Water will be diverted from barges and hillside reserves. Given the irregularity of surface water availability, ground water must be used to meet needs during dry years. Excess surface water during wet years is then used for artificial recharging of the aquifers that have been overexploited in dry years, thus avoiding negative effects on the aquifer and degraded water quality. In this area, Tunisia has gained a rich technical experience in a program that consists of recharging zones where underground water resources are over exploited with excesses from zones where surface water resources are plentiful. The cost of recharging is high. Water users appreciate and understand the value that recharging offers and are willing to pay the cost.

Tunisia is characterized by an arid climate, with varied relief, light vegetative cover and torrential rains. It suffers from soil erosion, which results in dam- clogging mudslides at a rate of 0.008/year. Monitoring of potential mudslides near dams regularly takes place. The sloping basins are continuously protected to minimize siltation and to extend the dam’s useful life. The degradation of soils in the sloping basins varies between 0.3 and 2 mm per year. Programs to conserve water and reforest areas near dams will extend the life of these facilities. The observed results on various reservoirs in use have permitted the evaluation of the lifespan of each reservoir.

Tunisia has briny water tables, situated essentially in the south of the country. Reverse osmosis has given this potential water source increased value by making it available for drinking water. Total desalination capacity for drinking water is about 80,000 m³ per day. The desalination of seawater offers a long-term alternative source of drinking water which could contribute as much as 50 million m³ in 2030. Thus, desalination of briny and sea waters constitutes an alternative that is more and more attractive as a source of drinking water in areas where water supplies are limited and do not meet standards, notably in the center and the south of the country.

Four important desalination plants operate in Tunisia: Kerkennah (1983), 3300 m³/day; Gabes (1995), 22,510 m³ per day; and two stations in Jerba-Zarzis (1999), 12,000 m³ per day each. Sixty smaller plants serve the industrial sector. In addition, the water law was extended in 2002 to permit private industry to produce and distribute desalinized waters in tourist and industrial zones when natural water is insufficient. Investments in this sector are encouraged by a set of specific subsidies.

The water pricing system in Tunisia is progressive, charging by quarterly consumption, and incorporating a fee for sanitation. The first quarter is considered necessary to meet basic human needs with consumption not surpassing 20 m³ per quarter. The last quarter considers consumption surpassing 150 m³ per quarter. The cost of a cubic meter of the last quarter represents 6 times the cost of a cubic meter of the first quarter. The price of drinking water is uniform throughout the country and is not seen as an obstacle to development. Drinking water charges allow for the recovery of operating and maintenance costs as well as capital investment in hydraulic systems.

Irrigation water use is subsidized by about 30%. Charges cover the cost of utilization and maintenance. Equipment renovation and the largest 50 repairs of the infrastructure are covered by the State. Reforms in the irrigation sector will be put in place and strengthened over the next few years to help alleviate the cost of the function and maintenance of irrigated lands, to encourage conservation and maintain the value of irrigated waters. Progressive pricing is used to manage demand. It prolongs the terms of investment, encourages water conservation and prevents waste. Studies conducted on progressive pricing have shown the sensitivity of users to changes in the price of water explaining the decrease in relative demand observed during the last years. The reaction of large consumers is particularly important as a tool for dampening demand. For small consumers, the response to price changes is weak because water is a basic need.

Meeting the drinking water needs of rural residents is a political imperative for Tunisia, especially in disadvantaged areas. Demand will reach 60 million m³ in 2030. Access to water in rural areas increased from 31% in 1987 to 82% in 2003, following efforts to improve conditions of life in this area. The objective of the national program is to increase coverage to 90% in 2006

with minimum coverage of 80%. When this objective is met, the cost per serviced inhabitant will increase from 400 dinars to 600 dinars to provide service to extremely dispersed residents. Individual wells, which are a well-established tradition in Tunisia, will be encouraged across the country. The maintenance of wells is controlled by the health services. The rural population is expected to stabilize between 3.2 and 3.5 million of which 825,000 will still need to be serviced in 2020. For the most dispersed population, private and mechanical cisterns are encouraged. Increased rural drinking water consumption has led to the creation of sanitation and resource protection programs. The construction of latrines, septic systems and wells will be encouraged and will improve hygiene conditions for 80% of the rural population. Source water protection is the responsibility of the health service. The management and maintenance of water infrastructure is carried out by 1500 cooperatives.

While exploring new water resources, Tunisia has already broached several reforms in the water sector that led to the introduction of demand management policies. Government officials in Tunisia have been involved in water related activities since September 25, 1885, when the first water decree was issued. The government’s role in the water sector was confirmed by the decrees of 1933, and 1936, which were then replaced by the 1975 water code, which has been updated every time the technical or economic conditions demanded it.

Before reaching its full water potential, Tunisia instituted an important change in the management of its water resources. This change is based on the allocation of a limited resource and the management of its growing demand. The administration of water resources in Tunisia relies on the continuous monitoring of water resources - surface water, subterranean water, treated water, and the development of technical tools that help with decision-making (for example, the propagation of vineyards, the reduction of water levels, the recharging of aquifers, desalination, the intrusion of sea water, etc.) The administration of water in Tunisia has required several successive reforms, whose objectives were:

• To encourage the valuation of water resources and to fight against all types of waste and corruption created by pricing systems adapted to the drinking water and irrigation sectors

• To develop a program of water conservation in the drinking water and irrigation sectors by monitoring and controlling consumption

• To encourage the participation of users in the management of collectives to control and improve efficiency

• To give value to non-conventional water resources by reuse of treated wastewaters in agriculture and desalination of briny waters for drinking water needs.

• To protect the quality of the resources against pollution using a widespread purification program

• To adopt water and soil conservation programs to reduce erosion and to increase aquifer recharge

These reforms have been discussed for a long time at many levels and in concert with the beneficiaries. The reforms introduced by the water code of 1975 included several actions to encourage water conservation and protect water resources. In 2001, new reforms were introduced classifying water as a national resource that everyone must preserve, protect, and use in a lasting

manner to satisfy the needs of citizens and the economy. The largest consumers are obliged to audit their use periodically (more than 5 million m³ per year in agriculture, more than 1000 m³ per year in the urban sector and 5000 m³ per year in the industrial sector). Consumption quotas are imposed during periods of scarcity. The development of non-conventional water sources (desalination and treatment of wastewater) is encouraged, allowing individuals to produce water and distribute it for their own consumption.

In Tunisia, investments in the water sector are designed to assure an equitable distribution of water resources. Small water projects (surface wells, hill lakes, hill dams, diffusion projects) are found in practically all the country. This explains the maximum cost of high mobilization from phreatic water levels (100%). In addition, the transfer of water and the interconnection of basins due to the North Water Plan Director’s project have permitted better division of water resources across the regions of the country.

Delays in improving access to drinking water in rural areas were overcome during the last few years, as service increased from 30% in 1986 to 82% in 2003. The pricing of drinking water assures an equitable allocation between the different levels of consumption. In fact, the transfer between sections is estimated at 20 million dinars per year. Thus the benefits of the country’s water infrastructure are shared among all the regions of the country and most of the citizens.

Assessments are carried out to identify needed actions that will safeguard the integrity of ecosystems and biological diversity. Ecosystems in dry countries are very sensitive and fragile. Monitoring of water levels, control of exploitation, and the establishment of protected areas all help to limit overexploitation and salt water intrusion. Impact studies of dams have led to the identification of mitigation measures to safeguard the hydro-geological and ecological equilibrium for upstream and downstream waters.

Protection of vital ecosystems will have growing priority with increased water use. It is evident that in the dry countryside, mitigation measures are difficult to design and costly to implement. Mitigation measures must be carefully evaluated to improve complementary interventions and to avoid irreversible degradation. The participation of multidisciplinary research teams with the universities is highly encouraged in Tunisia as a means to identify approaches that will lead to more sustainable development.

The determination of the capacity of a resource depends in large part on a firm understanding of its specific potential. Thus, careful evaluation of the resource is essential in water development projects. In Tunisia, the General Directorate of Water Resources is responsible for the evaluation of groundwater and surface water resources. It is also responsible for assessing the potential water resources. It manages a network of measuring stations (pluviometric stations, hydrological stations, piezometric stations) covering all the lakes of the country, as well as an information

center and tools for the study, simulation and analysis of aquifers and river beds of Tunisia. Existing studies allow for the planning, execution and the management of projects. The limited capacity of the resource is fixed based on these evaluative studies.

Thus, in order to maintain existing oases and allow for the creation of new oases in the south, capacity limits were established for the two major underground aquifers in Tunisia, the Complexe Terminale and the Continental Intercalaire (CI). The latter, CI, is one of the largest aquifers in the world, covering 600,000 km² beneath Tunisia, Algeria, and Libya. As a result of this regulation, withdrawal quotas have been determined for existing oases (0.7-1.0 L/s) and surface area quotas were established for new oases. The limited capacity of each phreatic water level limits the number of exploitable wells. If the limited capacity is reached, a suspension or safeguard decree is issued. The quota for allocation from large dams to each beneficiary is fixed. During dry spells, allocations between drinking water and irrigation are managed by the Minister of Agriculture. However, note that the limited capacity is exceeded in some local limited zones. These cases are very instructive because they show the breadth of negative effects when the limited capacity is exceeded in coastal aquifers.

The increased exploitation of natural resources in response to demand growth can only lead to disequilibrium. This disequilibrium constitutes a severe constraint for economic and social development and can lead to decreases in living standards and the loss of productive systems. In order to manage the situation, preventative actions must be taken to diminish the severity of the disequilibrium. In Tunisia, data relative to the availability of water and to the use of water resources is sufficient and therefore action may be taken in the management of this disequilibrium. Furthermore, extraction in Tunisia does not yet surpass the renewable resources except in some very limited and circumscribed zones. The global situation is not yet disturbing and will not be during the next 20 years according to the elaborated prospective study, “Economy of Water 2000.” In Tunisia, 84% of water resources are used by agriculture. The demand for water in medium and large urban centers is rising on average 2.5% per year. Improvement of agricultural efficiency will lead to the engagement of additional resources beyond newly mobilized resources in the future.

The interconnection of large networks of aqueducts in different regions of the country improves the capacity of the system to compensate for deficits in one area with excesses in others. This means of managing allows a better balancing of supply and demand. In the future, balancing supply and demand will depend more on the rational management of demand, because development of new resources (dams, recharging of aquifers, recycling water, desalination of water) will be more difficult and costly. The management of water demand in Tunisia has taken several forms. It has been considered a part of the master plan of water use and implemented in the development of projects with the introduction of a quota and restrictive technological tools (capacity of pumping stations, limits on building in tourist and industrial zones, surfaces of irrigation zones). However, the almost-urban escapes this planning, perhaps because the dynamic programs of rural development have limited scope. In Tunisia, the use of water changes in the urban and agricultural domains has helped to better manage demand and to better set value to the resource. In addition, public information campaigns have made citizens more conscious of

this resource and of the need to better protect it.

Demand management, as demonstrated in the case of Tunis and in irrigated areas, has proven effective and is likely to become more and more necessary to rationalize the use of water resources and to assure their long term availability. Demand management has been supported by judicial tools. Thus, the water code of 1975 permits central and regional public services to manage the resource by issuing authorization, establishing zones of safeguard and of interdiction, and controlling the management of water sources. In Tunisia, the coverage of the country was determined by the Regional Master Plans, integrating the homogeneous hydrographic basins: North, Central and South. Furthermore, regional master plans for rural drinking water covering each administrative unit have been established and have helped to improve access to safe water in rural areas. All the water development projects have been carried out, are being carried out or will be within the framework of these master plans, of which several are currently being completed.

To manage the water sector, Tunisia has developed a long term action plan. This plan allows the country to estimate water use 20 years in advance. This action plan, in addition to demand management programs, defines measures that permit technology to preserve, protect and conserve water resources and to develop new conventional and non-conventional resources.

Tunisia has conducted studies of the water sector, with a time horizon set at 2030. Several technical and socio-economical studies have been undertaken so the country may develop action plans and interventions to meet evolving water needs, allowing economic and social growth.

Thanks to the adoption of rational and modern management of its water resources, Tunisia, despite the scarcity of its water resource, has been able to develop its agricultural and economic sectors linked to the water resource in a sustainable manner. In the long-term future, all residents in both the cities and villages will have access to drinking water. Agriculture, which consumes 80% of natural water resources, has adopted a modern distribution system using water conservation and water reuse, attaining 20% artifical recharge in response to water and soil conservation projects, dams, and collinear lakes. The strategy of water resource mobilization and use constitutes an essential component of the economic and social development of Tunisia.

This strategy assures the security of food supplies, improves the quality of urban, rural and Saharian life and assures water supplies in the industrial and tourist sectors, while respecting the limited capacities of the ecosystems. It guarantees the continuity of exploitation of the resource while encouraging a larger participation of users in its management. This strategy integrates the management of surface and ground water resources as well as natural and non-conventional resources; and has set in place a mechanism of the optimization of water use through the efficiency of use, water conservation, reduction of loss and waste and the protection of water sources.