Friday, 03 July 2009 21:05
According to a new report Tunisia stands as a model to other countries in Africa and beyond in the successful management of water resources.
Throughout its history, Tunisia has suffered from droughts and floods. The occurrence has proven hard to predict as they do not follow any clear cyclical pattern. From the period 1640–1758, for example, no droughts can be documented in Tunisia, which is in marked contrast to modern times when the country has experienced approximately 30 separate events. Over the centuries, the country has developed sophisticated management systems to cope with the risks involved.
Managing its scarce and variable water supply is critical for Tunisia’s economic development, the World Bank report, “Water in the Arab World: Management Perspectives and Innovations” says.
The country takes the issues very seriously and has engaged in extensive public debates about water policy and the government has invested heavily in measuring, mobilising, and managing its precious water resources.
Tunisia has made significant progress in managing water, evolving from traditional practices to large government-led investments to store and transfer water. A third stage beginning around the turn of the millennium continues the physical investment but increases the emphasis on water management or “institutional engineering”.
Many aspects of Tunisia’s experience could be improved, but, on the whole, the country is an example of good planning and management.
Its success is all the more remarkable in that Tunisia is one of the countries in the Mediterranean basin least well endowed with water resources. The potential volume of available water, 4,836 Mm3 per year, is less than 500 m3 per inhabitant per year. This ratio will decline to 360 m3 by 2030, when the population will have grown to a projected 13 million.
To manage its variable supplies, Tunisia balances surface and groundwater stocks and flows within and between years. It uses dams and groundwater reserves to store surplus water in wet years and uses these stocks in dry years.
It also must distribute the water between different parts of the country. Maintaining a regional balance is an essential element in Tunisia’s water supply planning and management.
The population is concentrated along the coasts, where cities, industry and tourism are well developed. Agriculture is the largest water user and is located throughout the country except in the southern desert. Meanwhile, the country’s water supplies come mainly from the north and the interior of the country.
Water transfers, therefore, have been a salient feature of Tunisia’s long history from the Roman aqueduct at Zaghouan (built in 72 AD) to the modern-day Mejerda-Cap Bon Canal (1982), whose distribution networks go all the way to Sfax.
On a national scale, water resources are distributed unequally. The geographical distribution of different categories of water in Tunisia is as follows: Eighty-one percent of the country’s resources are in the north, 11 percent in the centre, and only 8 percent in the south.
Tunisia shares international surface water in the form of some rivers along the western border with Algeria. The two countries have reached agreements on how to mobilize and use this water, including agreeing the annual volume available in the relevant basins and how to distribute it between the two countries. The countries have also established a monitoring system, which enables both countries to track pollution as well as water volumes for the main international river, the Mejerda.
In addition, Tunisia has a considerable volume of international groundwater, located in the Djeffara coastal basin shared between Libya and Tunisia and, most importantly, in the Northwest Saharan Aquifer System, shared with Algeria and Libya.
The latter has more than one Mkm3 of water with very limited recharge, of which some 80,000 km3 are in Tunisia.
The three countries have established a commission to monitor this aquifer and have agreed to cooperate on its management to minimise cross-border impacts.
This is one of only two such agreements in the world. Tunisia uses water from this aquifer to irrigate greenhouse vegetables and dates.
Tunisia’s water policy aims to contribute to sustainable socioeconomic development while balancing two conflicting facts:
1. Limited water supplies and increasing cost to generate or store and transfer additional resources;
2. The growing demand for water.
The variability in water availability between years is huge. During the past few decades, the maximum potential volume of surface water was 11 billion m3 in 1969–70, and the minimum was 780 Mm3 in 1993–94. Variability is high everywhere but much higher in the South.
In the North, the wettest year was nine times wetter than the driest year. In the South, 180 times more water was available in the wettest year than in the driest.
This highly irregular supply affects the country in the form of floods and shortages of varying seriousness. However, the infrastructure available in recent decades has enabled Tunisia to store and transfer water, thus reducing the impacts of both flood and drought.
As monitoring has improved, and particularly as hydro-geologists have discovered larger volumes of groundwater available, the estimates of the amount of water potentially available in Tunisia grew substantially between 1968 and 2007.
Despite the increase in known resources, estimated water availability per capita is declining. For groundwater, the calculation of water available refers to the maximum volume of water that can be extracted annually from the country’s groundwater resources under prevailing technical and economic conditions without leading to the long-term exhaustion of the underground resource base. For surface water resources, the calculation takes into account resources available for annual extraction in 95 percent of years.
Tunisia has faced water quality problems as well. Less than half of the country’s resources have less than 1.5 g/l of salt and therefore meet health and agronomic standards. Of this water with reasonable salinity levels, 72 percent is surface water, 20 percent deep groundwater, and scarcely 8 percent groundwater. Surface water thus is used both for direct consumption and to improve the quality of other categories of water.
As difficult as it is to manage Tunisia’s water resources now, the job will only get harder in the future. Studies show that Tunisia can expect an increase in average annual temperature (2 degrees C on average), a modest fall in average precipitation (approximately 5 percent by 2030), and increased variability. In particular, extreme phenomena (droughts, floods, and strong winds) will increase in both frequency and intensity, with very dry years likely to occur more often. These changes will have serious consequences for water resources, ecosystems, and agriculture; for urban dwellers; and therefore for the entire economy and society.
For the past three decades, Tunisia’s water resource management policy has been based on mobilizing water resources. Strategies have been drawn up for agricultural water, rural and urban drinking water, urban sanitation, and the reuse of treated wastewater for agricultural purposes.
The Tunisian Ministry of Agriculture and Water Resources has developed a model to help operate the country’s water systems and manage the risks associated with both droughts and floods. It compares available resources with expected needs under various planning scenarios including estimates of when different major infrastructure investments will begin operation. This model simulates all foreseeable demands to enable the government to ensure that needs are met and to plan infrastructure needs well in advance. The tools used to create the simulations are constantly updated and enhanced to account for variables related to demand levels, the performance of modern technology, and perverse effects of reality.
The Ministry’s model consists of a number of separate information systems:
The first is the Optimal Water Resource Management model (known by its French acronym, G.E.O.R.E.) The idea of developing integrated water information systems was first proposed in a study that the government had developed over 1990–95. This study, “Water Economy 2000,” was intended to enable the country to respond to water demand on a national level over the coming decades (first to 2010, then 2030). It collected, analyzed, and synthesized a wealth of data and information pertaining to water resources and requirements, both qualitative and quantitative. In this way, relational databases covering resources and supply were established. All the country’s water resources (conventional and nonconventional) were identified at both the regional and national levels. For the first time in this type of study in Tunisia, a geographic information system (GIS) was used to identify where water resources are located and used.
The second information system is the agricultural map of the country, completed in 2004. This map is in fact a series of regional maps which give an overview of the agricultural area of each governorate, its resources, development potential, strengths, and weaknesses. The agricultural database was compiled into a GIS, comprising close to 50 layers of geographic data. The maps have the following objectives:
-To ascertain in a reliable and dynamic manner the status of a particular location regarding natural resources (land, water, forests), basic infrastructure (water, transport), and economics (processing, refining, and harvesting facilities for agricultural products)
-To ascertain the land allocation status
-To identify the gap between current and optimal land use by comparing the land use map with the agro-economic potential map
-To simulate and spatially visualize decision-making scenarios based on the modification of specific parameters, such as cost of entry, production prices, yields, and incentives.
The third information system is the National Water Information System, known by its French acronym as SINEAU. It is being completed and is expected to be publicly available. It combines three different water information systems: one on ground and surface water, one on water pollution and one on soil quality. The SINEAU links these three using a horizontal system of reference and unified spatial references.
It will establish standards for describing data and sharing it with different stakeholders as well as a system for managing and referencing the relevant data.
Over the past three decades, Tunisia has developed significant water infrastructure aimed at meeting its ever-increasing demand. The aims were to respond to different usage priorities and to enable flexible management. Decisions regarding the type and size of these storage and transfer facilities and their use were guided by some key constraints including the geological nature of the landscape and the location of the most demand for water supplies.
To ensure that water quantity is available in the place and at the time required, and to improve water quality through dilution, the infrastructure was planned using three guiding principles:
1. Allowing inter-annual storage to enable supplies to be regularized from year to year, taking into account repeated droughts;
2. Creating interconnected dams situated in the same catchment areas so that the system can capture any overflows of the dams in wet years;
3. Allowing water to be transferred from dams in one catchment to dams in another to balance stock levels in periods of regional drought and to improve water quality in particular reservoirs.
The hydraulic system for surface water was conceived essentially for the northern part of the country. In the system, 13 linked dams already are in place, and an additional 14 should be online by 2015, for a total of 27 interconnected dams.
To supplement its scarce natural supplies, Tunisia has a long experience of generating nonconventional water and of innovative investments. Its experience in reuse of treated wastewater, desalination of salt and brackish water, and artificial recharge of aquifers is instructive and indicates a concern for integrated management of the water cycle.
Since the 1970s, Tunisia has been formally reusing treated wastewater in agriculture and now has one of the world’s highest rates of reuse.
Almost all of Tunisia’s 194 Mm3 per year urban wastewater generated is treated to adequate standards.
Approximately 30 percent of it is reused in agriculture supplying approximately 7,000 ha of fruit trees and fodder, following strict sanitary standards. The country plans to invest in significantly increasing that share over the next decade. Experience indicates difficulties ensuring cost-recovery for wastewater reuse. At present, the service is subsidized. In addition, Tunisia uses treated wastewater for environmental purposes, in one case, to ensure flows to an ecologically important wetland.
Despite being a country not endowed with energy resources, Tunisia has experience with desalination of brackish and saline water. Desalination began in 1983 in Tunisia. The national agency responsible for drinking water, SONEDE, has capacity
of 58,800 m3 per day.
Private operators have an additional capacity of 44.000 m3/day, mostly for tourism, although with some capacity in industrial enterprises and high-value agriculture. In the South, the authorities have been able to use reverse osmosis technology to convert brackish groundwater into drinking water.
The government subsidizes the private sector to invest in desalination and considers this technology a key part of the long-term water management strategy for the country. It plans to increase public sector installed capacity to 50 Mm3 day by 2030.
In addition, the country has long experience of artificial groundwater recharge. This is a way of storing surplus water from one season for use during dry periods. The construction of small dams included spate irrigation infrastructure to channel flood water. In addition to helping manage surface water flows, investment has had a major impact on aquifer recharge.
Furthermore, Tunisia has projects using quarries, old wells, and direct injection to increase aquifer recharge, in some cases including recharge with treated wastewater. To avoid potential contamination, these schemes usually are toward the mouth of the aquifers. One trial scheme uses treated wastewater at the mouth of the aquifer to protect against saline intrusion. The government plans to increase the volumes of artificial aquifer recharge to more than 200 Mm3 per year in 2030 through small dams, check dams, and soil and water conservation investments in upper watersheds.
The irrigation sector consumes close to 80 percent of Tunisia’s extracted water. Tunisia has approximately 420,000 ha of land that could be irrigated through both public and private schemes. Of this, 400,000 ha are actually irrigated. The government’s strategy aims to serve these lands with water, assuming that water is available, by 2010. The sector now uses approximately 2 billion m3 per year. Demand should stabilize at 2.1 billion m3 by 2010.
Groundwater extraction has increased continuously since 1997, rising from 2,161 Mm3 to 2,638 Mm3 in 2006—an increase of approximately 26 percent over 15 years. Yet, withdrawals are becoming unsustainable, while exploitation of deep groundwater is increasing slowly. On the positive side, there is potential for more or better use of surface water. In the last decade, overall usage rates of surface water have been low.
The lack of good-quality water is becoming increasingly acute in the wake of unpredictable climate patterns. Thus, the country needs to find a way to improve the value-added from the water allocated to the agricultural sector.
A technical, economic, organizational, institutional, and legislative framework has been set up to maximize the country’s irrigation potential as efficiently as possible. Water conservation constitutes a key component of this strategy. Since the end of the 1980s, with the introduction of conservation measures in irrigated areas, consumption per ha has begun to decline sharply, falling from 6,200 m3/ha in 1990 to approximately 5,500 m3/ha in 2005.
In 1995 Tunisia’s water administration adopted a National Programme of Irrigation Water Conservation (PNEEI). Its purpose was to rationalize the use of water to ensure that the maximum economic value is derived from irrigation and to keep water demand at a sustainable level.
The programme provides a 40 percent–60 percent subsidy for efficient on-farm irrigation equipment, (upgraded gravity irrigation, sprinkler irrigation, and drip systems) with the exact rate depending on the category of agriculture.
The program aimed to install efficient on-farm irrigation equipment on 90 percent of Tunisia’s 400,000 ha of irrigated land by 2006 and to improve irrigation efficiency to a level of at least 75 percent by the end of 2006.
As of June 2006, the irrigated area with qualifying conservation systems in place covered close to 310,000 ha, or 75 percent of the irrigated area. The implementation rate has been running at 15,000–25,000 ha per year.
The National Authority for Water Exploitation and Distribution (SONEDE), the body tasked with producing and distributing drinking water, has set up a strategy to ensure efficient water use.
Measuring the volume of water produced and distributed plays a key role in water management. The government’s strategy is to equip every water system with an appropriate means of measurement and to divide networks into sections through the installation of local metering systems. The thorough deployment of meters will ensure an effective mechanism for tracing leaks. As of 2007, all of the reservoirs producing drinking water were equipped with either meters or other means of measuring outflows.
The government intends to equip all drinking water supply systems with appropriate regulation equipment. By 2007, 96.6 percent of supply systems (gravity and reverse-flow) had been fitted.
Tunisia’s system for evaluating and monitoring water conservation, along with a land survey carried out in 2001, has enabled a mid-term assessment of the National Water Conservation Programme. The results confirmed that the programme was both effective and economically viable in the agricultural sector. In particular, the evaluation shows that an extremely dynamic response from stakeholders led to a significant increase in the area of land equipped with water conservation systems.
Promotional campaigns using a variety of means of communication have contributed greatly to water conservation in irrigation.
The unavoidable reality facing Tunisia is the necessity to conserve and derive maximum benefit from its limited water resources. Substantial future savings that are needed will have to come from the major water-using sectors, especially agriculture, which consumes almost 80 percent of Tunisia’s available water resources.
Tunisia can expect a future of water shortages exacerbated by more frequent droughts and climate change. Water supply management therefore must improve the operation of water infrastructure and harness technology to make optimal use of existing resources.
The rationale for creating new irrigated areas should be examined in light of future water demands. Implementing a demand-based water management strategy will strengthen the case for a realignment of water sector institutions.
With increased involvement of users, water planning and implementation will see improved performance. Therefore serious thought will need to be given to the ways in which these water users can be brought in to participate in defining Tunisia’s water management policy and strategy.
Global Arab Network
This article is based on a chapter from the major report “Water in the Arab World: Management Perspectives and Innovations” published by the World Bank.
Saturday, July 4, 2009
Water Management in Tunisia