Sourcebook of Alternative Technologies for Freshwater Augmentation in West Asia


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<Sourcebook of Alternative Technologies for Freshwater Augmentation
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Case Study 2: Hill Reservoirs in Lebanon

Hydrological studies listed over 40 watercourses in Lebanon. Of this total, 17 are permanent and 27 are temporary. There also are more than 4,000 mountain springs with discharges exceeding 10 liter/second. Because it is difficult to secure the water resources required for various applications in the mountainous areas because of their karst nature, as well as difficulty in obtaining groundwater through drilling wells, Lebanon has focused attention on the construction of hill reservoirs. The Green Plan is the most important project aimed at enhancing socioeconomic development in Lebanon through the agricultural sector. Work started on this project in 1963, and it was in operation in 1965. Among the components of this project was construction of irrigation water reservoirs. Because the volume of hill reservoirs does not typically exceed about 50,000 m³, about 650 of them were constructed, with a total water storage capacity of about 1,079,640 m³. Unfortunately, work on this project ceased because of the intervention of the war. However, some efforts are currently being exerted to put it into operation again.

Nevertheless, within the framework of the other efforts exerted, a number of hill reservoirs were constructed. A study also was conducted to select a number of sites for constructing the hill reservoirs to meet the requirements for water supply and agriculture. Despite the favorable topographic and climatic conditions, and the need for water, Lebanon did not significantly expand its efforts in the construction of hill reservoirs, due primarily to the circumstances in which the country has found itself over the past 17 years.

Technology Description

This technique is based on the construction of hill reservoirs (small dams) on watercourses or cisterns, in the form of ground pits in mountainous areas, in order to collect the runoff water from melting snows. These cisterns are either concrete lined (if used for drinking water) or they are earthy (after the soil is compressed to avoid filtration). When the soil is of non-suitable nature, the cisterns are sometimes lined with plastic sheets. The three hill reservoirs constructed were low-height small dams (10-15 m). Reservoirs may be constructed in natural low grounds that are made deeper and prepared for storing the water conveyed from the adjacent areas, as is being implemented through the Green Plan in Lebanon.

Only a limited number of hill reservoirs were constructed for domestic uses, due to the difficulty to guarantee the purity of the water for human use. However, the main hill reservoir constructed for this purpose is Jouret El Bullout at Azzarour in the Senien area, with storage capacity up to 45,000 m³. It is used basically to compensate for potable water losses in the Al-Maten area. The dam is constructed of reinforced concrete, with the reservoir being circular in shape and built on calcite rocks. The hill reservoir is recharged by collecting the water from small springs and conveying it to the hill reservoir, or else collecting surface runoff waters from melting snow (resulting from the region’s high rainfall in the form of about 1,500 mm of snow/year). In a recently-conducted study on the feasibility of constructing hill reservoirs for drinking, four new reservoirs were proposed in Almaten areas, Beir Alshaikh, Alzahereia (Alia and Ashouf), Zohour Alkesemani (the higher Maten) in Ashouf area, and Majdalia in Alia.

As previously noted, most of the hill reservoirs constructed in Lebanon are used for irrigation. They include natural hill reservoirs formed on the 7,500 m elevation, where water is available through the end of August, and the water is used for irrigatin of some crops and livestock watering. Major hill reservoirs are Zainieh (800 m length and 400 m width) and Ram Al- Zainieh (600 m length and 400 m width). These hill reservoirs are fed from rainwater and melting snow (rainfall up to 1200 mm/year). The remaining hill reservoirs are artificial. They are either constructed separately, or within the framework of the Green Plan project. On the governmental level, the major hill reservoirs are Alkawashra in northern Okra, and Dahr Aldarja in Jezzin. On the level of the private sector, efforts were exerted to construct small-size hill reservoirs for collecting rainwater and melting snow, with storage capacities each less than 25,000 m³. Dams constructed on these hill reservoirs are primarily of a marl-type soil, although some are built of concrete.

Extent of Use

There is considerable interest in Labanon in the construction of hill reservoirs and small dams. When the Green Plan project began, the goal was to secure irrigation water by setting up water cisterns in mountainous areas that would benefit from this technique. Overall, this project benefitted about 43,000 farmers and 931 villages. Six hundred fifty cisterns were constructed, with a water capacity of 1,079,640 m³ during 1965-1970. They are earth or reinforced-concrete types (Figure 57). In a 1975 study, the construction of 156 hill reservoirs was suggested. Of this total, Lebanon approved 38 for execution, but unable to construct them. Work has currently resumed to construct 15 of the 38 approved hill reservoirs, primarily to secure water for irrigation and livestock watering. Theconstruction of 8 hill reservoirs for drinking water supplies also was approved.

Operation and Maintenance

Cisterns of this type are not difficult to operate or maintain. The required maintenance tasks include cleaning them of sediments when they are empty, as well as cleaning the watercourses discharging into the cisterns. These tasks are included within the responsibility of the municipality, although the population benefitting from it may also contribute to them.

Level of Involvement

Two types of constructed hill reservoirs or cisterns can be distinguished. These types are executed by the private sector or non-governmental organizations and consequently are of small size. The second type is carried out within the framework of the Green Plan project. The types of support offered by the project can be summarized as follows:

Figure 57. Hill reservoir in Lebanon

Financial Support

To contribute to the costs of land reclamation;
To secure low-cost agricultural machinery;
To construct water irrigation cisterns;
To distribute seeds at very low prices;
To distribute grains to farmers in return for their constructing channels, cisterns and fulfilling land reclamation requirements.

Technical Support

To study the physical land characteristics of land;
To determine proper irrigation methods;
To offer advice concerning channel and cistern construction, as well as land cultivation;

Regarding individual financial contributions, the farmer used to pay about 15-20% of the total cost, with the Green Project funding the remainder as a loan with an annual 1% interest rate. The farmer pays the loan with easy payments beginning in the 6^th year and extending over 10 years. This contribution was subsequently modified, with the farmer only contributing 18-39% of the total cost, and the project undertaking to pay the remaining cost.

Costs

At present, there is no data on the construction costs of water cisterns or hill reservoirs. Based the previous data available on the Green Project for the year 1970, the total cost for the construction of 650 hill reservoirs with capacity 1079640 m³ was 1221382 Lebanese Lira (approximately 600000 US$, in 1970). Consequently, the cost of one cubic meter during this time was about 1.6 US$/m³. At present, after taking inflation into consideration, the price may reach 20 US$/m³. This cost estimate does not consider the project lifetime and its future return.

Effectiveness of the Technology

Hill reservoirs have proven to be beneficial in securing the water required for irrigation, livestock watering and potable water needs. This was clearly demonstrated with the benefits of the Green Plan project within 5 years of its execution, where 35% of the reclaimed lands (3,637 hectares) were irrigated. Based on these results, there is a trend in Lebanon to increase the number of hill reservoirs, and new studies indicate there presently is the potential to construct 69 hill reservoirs.

Suitability

Under the current climatic conditions, status of water resources and the geological characteristics which do not facilitate the availability of groundwater, there is an impetus to expanding the construction of hill reservoirs in Lebanon. High rainfall volumes in most areas of Lebanon also facilitate expanded construction of hill reservoirs in irrigation projects.

Advantages

The advantages of this technology are as follows:

It allows for securing of high-quality water for agriculture and drinking purposes;
It reduces soil erosion resulting from runoff water detention;
It provides a means of securing irrigation water sources during the summer months;
It increases the area of agricultural lands;
It facilitates the beneficial use of previously-wasted rainwater;
No power is required, particularly if the hill reservoirs are constructed in elevated areas allowing irrigation of low areas by conveyance of the water under gravity.

Disadvantages

The disadvantages of this technology are as follows:

The lake and reservoir construction costs can be high if their volume exceeds 10,000 m³;
The hill reservoirs require continuous maintenance;
It is necessary to protect the hill reservoirs from pollution (resulting from animal watering or other causes);
If the hill reservoir is used to provide potable water, restrictive measures are necessary to protect the water from pollution;
Detailed geo-engineering studies are required for the reservoir bottom layers prior to construction, to guarantee effective water storage, thereby increasing construction costs.

Further Development of the Technology

The public and concerned authorities are convinced of the feasibility of constructing hill reservoirs to increase the utilization of available water resources. For this purpose, the Lebanese Ministry for Agriculture has assigned an Arab organization to conduct a feasibility study for the construction of small dams and hill reservoirs. In the framework of this study, 27 sites have been selected out of a total of 90 potential sites. This selection represents the base for future expansion of this technology, especially in middle regions of Lebanon that lack the necessary water resources for development.

Information Sources

Contacts

Mohamed Al-Khouly
Director, National Remote Sensing Center
National Council of Scientific Research
P.O. Box : 11-8281
Beirut, Lebanon
Tel: 509845/6
Fax: 409847

Mahmoud Ahmed Sabra
Director, Rural Development and Natural Resources
Ministry of Agricutlure
Beirut, Lebanon

Ministry of Agriculture
Directorate of the Green Plan Project
Beirut, Lebanon

References

Arab Organization of Agricultural Development. Small dams and hill reservoirs construction project of the Republic of Lebanon. Preliminary Investigation Study.

Arab Organization of Agricultural Development. 1994. Small dams and hill reservoirs construction project of the Republic of Lebanon. Preliminary Investigation Study, Khartoum.

Bassam Gaber, Foad Saad and Hasan Gafar. Current situation of hill reservoirs in Lebanon. Ministry of Water Resources and Electricity, Lebanon.

Ministry of Water Resources and Electricity. Water documents from the Al-Litany Department. Lebanon.

M.E.E.C. 1971. The Green Plan-A general evaluation of performance. Middle East Economic Consultants, Breirut.

Green Plan Project. Project publications. Ministry of Agriculture, Green Plan Project, Beirut, Lebanon.

Mohamed Al-Khouly. 1998. The technologies used in Lebanon to utilize freshwater. Local report.

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