National Water Security

The chapter introduces to concepts and debates that dominate the water issue at the global scale. First, the world water balance outlines contributions made to the development of understanding renewable freshwater resources on Earth, as well as withdrawals and impact of human actions on the hydrological cycle. The water footprint concept applied at global scale makes it possible to specify the respective places occupied by blue, green and virtual water in the world budget. A second part focusses on water balance of arid countries. The following part deals with impacts of anthropogenic activities on water resources, particularly acute in arid countries where strategies of massive resource mobilization and transfers are faced with problems related to water scarcity and competing demands. The perspective of climate change exacerbates an already critical situation in some countries under water stress: increased exploitation, quality deterioration, overexploitation, soils and aquifers salinization, negative impacts of dam reservoirs on groundwater recharge. The last part presents the main principles, concepts and instruments of water policies. Among the basic principles should be mentioned the user pays and polluter pays principles, the precautionary principle and the principle of subsidiarity. As regards the instruments, different approaches are presented: integrated water resources management, water demand management, watershed-based management, participatory management. Mention is also made of aspects relating to the economic dimension of water, value and pricing, as well as water data and water information systems.

This chapter attempts to place the reader in tune with current trends, debates and sometimes contradictions that dominate the issue of water on a global scale. A historical overview traces the progress of water status, describes the international community action in addressing the water issue and analyzes the implementation of the right to water. It is followed by a review of water security and water scarcity assessments methods focussing on the progress achieved towards more holistic approaches which go beyond conventional assessments of water availability and water scarcity, to include the multiple dimensions of water security. At National scale, water security is a central political issue for which public authorities develop appropriate strategies to secure supply for all uses and promote human well-being through socio-economic development. These aspects fall within the concept of National Water Security with its “soft” and “hard” components. The essential elements of a framework that conceptualizes the National Water Security concept  are developed, with particular emphasis on the arid and semi-arid countries. Considering water scarce regions, the starting point of National Water Security is to raise awareness on the limits of the resource in order to guarantee the natural environments conservation and the protection of the resource.

Tunisia has implemented a network of hydraulic facilities allowing to ensure safety about drinking water supply of the whole urban population and a large part, although unequally, of rural regions. Irrigation has been developed on 420,000 ha, or 8% of arable land which contribute nearly a third of the agricultural production value. The water facilities are involved, in addition, to mitigate the flood-related damage and droughts. Urban sanitation has also developed favorably in large cities, but yet very unevenly in rural areas. All these achievements have contributed to improve food and health conditions. However, this development admits an objective limit which is the threshold of exploitable resource. The policy of increasing supply of conventional resources begins to reach its limits and corollaries of accelerated water resources development were clearly identified since the early 1990s: overexploitation of many shallow and deep aquifers, water salinization in some of them, soil salinization in some irrigated areas. In this context, integrated management of the resource including demand management, is introduced to meet the growing needs expressed by various sectors. Important changes are taking place and reforms are being implemented to protect water resources, control production and use of non conventional water resources, better manage hydrological risks, anticipate conflicting sectoral interests by mobilizing all stakeholders, modernize the regulatory framework and develop appropriate planning.

Tunisia’s rainfall resource is 36 km³/year, generating flows for 4.8 km³/year as blue water. Groundwater withdrawals are 2 km³, and many aquifers are overexploited: the national groundwater overexploitation is 20%. The chapter presents updated information on water facilities: large dams, hill lakes and hill dams, water-table and deep aquifers, with a focus on weakly renewable resources and exploitable resources taking into account the water salinity criterion. The water resource of rainfed agriculture (green water), is 13 km³/year, increasing to 19 km³/year when including rangelands. The total blue water withdrawals are 3.0 km³, of which 0.64 km³ for municipalities and 2.2 km³ for irrigation. Coastal areas are more populated and require water from other better-endowed regions: the whole country is marked by large water transfers from West to East. The infrastructure includes comprehensive resource monitoring, in relation to groundwater whose exploitation increased 3.5 times over the past 40 years. A specific section is devoted to the anthropogenic water cycle, where a precise assessment of all water uses is provided: from withdrawals, through allocations and actual uses, to consumptive uses and returns to the receiving environment. The last part establishes the complete water balance of Tunisia, with a first prognosis of all rainfall resources processing.

After a preamble devoted to water demand management (WDM) principles in Tunisia, the chapter examines aspects relating to water supply and management conditions, and major challenges in water use key areas: drinking water and agriculture. Use of non conventional waters: desalination and treated wastewater reuse, are considered as an extension to demand management policies. For drinking water, WDM includes technical measures and pricing. Institutionally, the question arises of the long-term sustainability of the current dichotomous management for drinking water supply and sanitation. In irrigation, WDM strategy is based on modernization of collective irrigation systems, water savings at the plot, and pricing policies. Later sections analyze non conventional resources, desalination and wastewater recycling. Number of constraints hinder recycling large-scale development: inadequate treatments against salinity, restrictive uses due to treatment variability, state of repair of treatment plants, not conducive to maintaining acceptable quality levels. In 2010, the total desalination production was 40 million m³/year. Future desalination programs forecast to bring this capacity to almost 120 million m³ in 2030. The country is not equipped to face the challenges of such a perspective, but some measures may help, like appropriate regulations and standardization, institutional organization to plan, implement, evaluate and monitor the national water desalination program.

The chapter addresses some of water issues still being debated, for which no definitive solution has yet been seriously considered, and have not yet obtained a consensus among water experts, water actors and the civil society. The questions that preoccupy Tunisia serve to organize the debate around two main topics: (i) How to secure the water supply? This theme covers physical and technical issues that Tunisians, engineers and decision-makers traditionally know how to formulate and resolve, but divergences persist concerning opportunities, timelines, methods of approach and implementation. This topic includes: new ways to improve the national water balance, underground storage of surplus water from the wetter North, internal security of water resources and hydraulic facilities, coping with groundwater overexploitation, securing water quality, protecting the status of water and human health. (ii) How to achieve good water governance? This theme covers legislative, institutional, regulatory and cognitive issues, most of which are subject to wide-ranging debates initiated some twenty five years ago by the Tunisian water community. These issues, still open to debate, concern: the institutional reforms, the Water Code revision, how to better use water for more equity and efficiency, developing and better valuing the knowledge on water, sustainably manage transboundary basins by consultation mechanisms.

The chapter considers the detailed water balance related to food needs of Tunisia. The water footprint of agricultural production, including rainfed crop production, irrigated agriculture and animal production is estimated on average at 12 km³/year. Overall, the green water contribution, including rangelands, represents three quarters of the agricultural production. The remaining corresponds for a half to blue water footprint associated to irrigation and for the rest to virtual water imports embedded in fodder and cereals for livestock production. Assessment of virtual water fluxes associated with food products trade shows that virtual water imports has increased significantly in recent decades going from less than 2 km³/year to more than 8 km³/year from 1970 to 2000. Simultaneously, virtual water exports have doubled, from 1 km³/year to over 2 km³/year. Green water share represents more than 75% of the virtual water exports, and the share of BW represents 12%, more than half of which from dates exports. The virtual water coverage ratio, (exports to imports), has gradually deteriorated, from 80% in the early 1970s to 30% in the late 2000s.

Water requirements for food demand in Tunisia have more than tripled over the past four decades, and amount to more than 16 km³ in 2010. As the population has nearly doubled during the same period, water requirements for individual dietary recorded an increase from about 1050 m³/year/capita in the early 1970s to nearly 1600 m³/year/capita in the late 2010s. To draw up an outlook of water-balance future, long term perspectives for all kinds of water resources are carried out with various demographic hypothesis. The blue water evolution relies on substantial increase of non conventional water and stronger water uses control. The blue water footprint of crop productions will rise from 1.4 km³ in 2010 to 2.1 km³ by 2050. At the same time, green water involved in food production is expected to increase by almost 25%. With the medium variant of demographic projection, the water balance deficit would be around 13 km³ in 2100 and the water dependency index, ratio of imported virtual water minus the exported one divided by the water equivalent of the food consumption, will increase from 39% in 2010 to 48% in 2100. With higher population hypotheses, the water dependency index could reach 62%, and perhaps even more under the global warming effect.

The Tunisian case provides a conceptual model of the National water security paradigm with its multiple dimensions. The main idea that emerges from the holistic view of water resources is that water scarce countries should cope with all water resources: improvement of water use efficiency, valorization of rainfed agriculture, development of alternative water resources, and optimization of virtual water fluxes. All components of water availability and water demand should thus be identified and accurately estimated. This integrated vision aims at valorizing all water resources and leads to achieve integrative Blue, Green and Virtual Water Management. Much of mobilized blue water is used in agriculture and irrigation sustainability requires decisive action in strengthening demand management measures. The green water contribution to food production is considerable (about 87%) and consolidation of food security cannot be conceived without decisive progress in the green water valorization. Last, virtual water flow, which appears on first analysis as an adjustment variable, must be optimized taking into account the limitations of internal water resources and the benefits of the comparative advantages that domestic agriculture can develop.