Since it is difficult to obtain the necessary water resources from the mountainous areas because of their karst topography, and because it is difficult to obtain groundwater by drilling wells, Lebanon has focused on the construction of hill reservoirs. The Green Plan was established in 1963 for the purpose of executing agriculture infrastructure projects. These include the building of hill reservoirs.
Before the Green Plan was inaugurated, a number of hill reservoirs had been constructed. A study was conducted to select a number of sites suitable for the construction of hill reservoirs. Despite the favourable topographic and climatic conditions, as well as the need for water, Lebanon did not significantly expand its efforts in the construction of hill reservoirs until the establishment of the Green Plan.
A new technique for building hill reservoirs
A new technique is being implemented in Lebanon. It is based on the construction of hill reservoirs 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 a non suitable nature, the cisterns are sometimes lined with plastic sheets. The three hill reservoirs that have been constructed were low-height, small dams (10-15 meters high). Reservoirs may be constructed in natural low grounds that are made deeper and prepared for storing the water that is conveyed from the adjacent areas, as is being carried out within the framework of the Green Plan.
Only a limited number of hill reservoirs have been constructed for domestic uses, because of the difficulty in guaranteeing the purity of the water for human use. The main hill reservoir that has been constructed for this purpose is Jouret El Bullout in Azzarour in the Senien area, with a storage capacity of up to 45,000 cubic meters. It is used basically to compensate for potable water losses in the Al-Matn district. 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. In a recently conducted study on the feasibility of constructing hill reservoirs for drinking water, four new reservoirs were proposed in Al-Matn: Beir Alshaikh, Alzahereia (Aley and Ashouf), Zohour Alkesemani (the higher Matn) in Ashouf area, and Majdalia in Alye.
Hill reservoirs have proven to be effective
There is considerable interest in Lebanon in the construction of hill reservoirs. When the Green Plan project began, the goal was to obtain irrigation water by building water cisterns in mountainous areas that would benefit from this technique.
Overall, this project has benefitted about 43,000 farmers and 931 villages. From 1965 through 1970, six-hundred fifty cisterns were constructed, with a water capacity of 1,079,640 cubic meters. They are earth or reinforced-concrete types. In a 1975 study, the construction of 156 hill reservoirs was suggested. Of this total, Lebanon has approved 38 for construction, but was unable to carry out the work. Work has currently resumed on the construction of 15 of the 38 approved hill reservoirs, primarily to obtain water for irrigation and livestock watering.
Hill reservoirs have proven to be beneficial in obtaining the water that is required for irrigation, livestock watering, and potable water needs. This was clearly demonstrated by the Green Plan project within five years of its execution, as 35 percent of the reclaimed lands (3,637 hectares) have been irrigated. The trend is to increase the number of hill reservoirs, and new studies indicate that there presently is the potential to construct 69 hill reservoirs. High rainfall volumes in most areas of Lebanon facilitate the further construction of hill reservoirs.