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Newsletter and Technical Publications Operation and maintenance Operation and maintenance works vary on the basis of the technology used. Cisterns, for example, are completely excavated in rocks if they are solid, or above the ground surface where all precautions are taken to decrease water leakage from cistern walls, contamination and wall abrasion. To increase the incoming water volume to the cistern, the efficiency of the feeding area can be increased if it is lined with thin concrete layers or compressed clay. Safe design specifications should be applied when computing the cross sections of cisterns, and a suitable lining material also should be selected to minimize leakage from the walls or the cistern bed. It is recommended that the building materials available at the cistern site be used, as well as selecting appropriate locations for harvesting the rainwater that guarantee the cistern is filled even during the driest periods and with the minimum quantity of equipment. If small dams are used, their safety depends on the basic hydrological conditions in the watershed basin and the relevant hyrdrometric measurements, in order to determine the seasonal water contributions for the valley or river course. The relation between the annual rainfall rate and the runoff coefficient must be determined, and the geologic and geomorphologic conditions at the dam site also must be identified. The dam is typically designed to sustain the worst expected conditions. Technical management for operating the dam also is required, as well as collection of relevant data on annual storage volume, methods of water distribution and regular maintenance, in order to avoid negative impacts such as sedimentation at the dam structure or spillway. The construction of small dams generally requires technical staff with good expertise and experience, as well as the availability of modern equipment. It is noted that Hafayer are easy to execute if they are of small capacity and used to supply water for supplemental irrigation or livestock watering. If they are to be designed to secure drinking water for villages or small cities, however, hydrological studies must be conducted, including carrying out engineering works and technical supervision during the execution and management stages of the Hafayer. The required tasks include hydrologic studies to deter,ome the capacity of the drinking water source, exploratory surveys on soil types and properties, and topographic surveys. A study on operation and management of the Hafir also is required. Designs must be prepared on the Hafir water feeding system, the water abstraction, and the protection of the stored water from contamination. The Hafir also must be protected from occasional high floods. Other tasks include procedures for securing water distribution through networks to the villages, and constructing disinfection and purification units. The runoff coefficient in the water supply area also must be improved, using conventional methods or industrial soil treatment. Evaporation losses must be reduced with the use of floating plastic sheets, and lining also should be applied in the form of impervious soil or plastic sheets. Spades/streams/Mahafir are constructed using the excavated earth material around the excavated pit, either open from two sides or one side in the direction of the water flow. Their capacity typically does not exceed a few thousand cubic meters. They are executed either manually or mechanically, based on available capabilities. They do not need specialized water inlet or outlet equipment, except when the water is to be used for irrigation or agricultural purposes. Relevant data on climate, geology and soil studies must be available for diversion dikes for irrigation or spreading water. The soil also must also be loose in the area where the water is to be spread, in order to increase filtration. It also should be rich in organic material. The land slope should not exceed about 3 per thousand, and should be sufficiently uniform to guarantee a wide spreading of the water. The water spreading area should be large with no major protrusions. Water-spreading dams and dikes also require periodic maintenance to ensure long operational lives. A study on the quantity and types of deposited sediments transported annually also is recommended. An accurate study on the hydrologic conditions in the suggested area for the dam and the water spreading area, including an estimation of the maximum and minimum water flows, also is recommended. It is also important to study the locations of the water inlets and outlets, to ensure the easy distribution and spreading of water in the proposed area. In regard to dikes, a suitable means of conveying water to reduce water losses should be developed, either through construction of earth channels lined with plastic or cement, or construction of suspended concrete channels or plastic pipes. Level of Involvement Runoff water harvesting technologies have been known for a long time. Attention to these technologies, however, has increased in recent years as a result of a depletion in groundwater resources because of increasing water demands, particularly from wells. This increased attention also is a result of an increasing awareness of the importance of utilizing all available water resources, including rainwater, to meet various development requirements. It is clear that the involvement of all the governments in the region in expanding the relevant structures is essential, particularly for constructing small dams. This technology is becoming increasing utilized in countries where it is showing promise. The support shown by governments in regard to cisterns and Hafayer, however, is limited. As a result, local people typically carry out the construction and maintenance work at their own expense, although they have limited areas in such cases.A number of such projects have been implemented in various countries in the region, including Jordan and Syria, with the goal of increasing the use of harvested runoff water. The latter are primarily research projects carried out in cooperation between the governments and international organizations.Some governments still supervise the execution of cisterns and the distribution of their water in accordance with specific regulations. The efforts exerted by the government of Yemen in construction of water storage structures is illustrated in Table 2. Cost It is difficult to estimate the cost per cubic meter for the water provided through the various technologies of runoff water harvesting illustrated in the previous sections.Accurate estimates depend on such variables as the conditions of the area, the volume of the facility and the extent of water use. Some studies suggest that the construction cost of the cisterns is between US$ 25-40/m3.If well executed, their operational lifetime will be virtually unlimited due to the low maintenance costs. Table 2. Government-funded small-scale storage structures in Yemen
On the other hand, the construction cost of small dams is somewhat high.The construction cost of a dam with a storage capacity of about 1.0 million m3 of water is estimated to be US$ 400,000 (US$ 0.4/m3). In Palestine, the cost of constructing an agricultural catchment pond of a volume of 3,000 m3 is about US$ 25,000, including the cost of the land with an area of about 5,000 m2. The cost of constructing an agricultural catchment pond of a volume of 250 m3 in Gaza, using prefabricated concrete, is estimated to be about US$ 6,100. If it is considered that the estimated life span of the structure is at least 20 years, it is clear that the bitumen pits are cheaper that metal tanks used for the same purpose. Effectiveness of the Technology The efficiency of this technology depends primarily on the benefits achieved because of its execution.The rainwater harvesting projects executed in Jordan, for example, such as improving the Al-Hammad basin (A-Rowaished- 50 mm rainfall/year), resulted in improvement of about 60,000 km2 of pasture, in addition to the livestock development. The volume of harvested water totaled about 2.6 millions m3. The projects of the authority of the Jordan valley have resulted in the construction of Hafir with a total storage capacity of 80,000 m3 of water.In Al-Mowaker projects, runoff water is controlled with earth dams with a capacity of 115,000 m3, with the water being utilized for supplemental irrigation.The area of the main basin is about 70 km2, with a project area of 0.2 km2. The water is used for irrigation of field crops, fruit trees and fodder shrubs. Through the development project of the Al-Zarka river basin, with a project area of 150 km2, the volume of harvested water reached about 150,000 m3/year (with a rainfall of 350 mm/year), with the water being used for irrigation (olive, nuts, field crops). In fact, the range of these technologies offers ideal solutions to supplying water resources at many locations. Cisterns help secure water for areas that otherwise lack sufficient water resources, including the southern region of Syria and the steppe region.Small dams help secure drinking and irrigation water for rural and steppe communities. They also contribute to agricultural expansion and economic development via construction of factories or electric power generation, as well as increased tourist activity. The agricultural catchment ponds in Palestine also have contributed to securing a water supply, and have proved to be a substitute for wells during the dry season. In fact, the water they supply is sufficient to meet the water requirements that otherwise would have had to be contributed from groundwater sources during the period between February to July. This means that water is stored in these ponds for a period of five months.The volume of evaporation losses was estimated to total about 17% of the total volume of stored water. Suitability Runoff water harvesting technologies are suitable for areas lacking a sustainable surface or sub-surface water supply for meeting different development activities, or which are subject to large changes in rainfall rates. In addition, the long dry season that limit the ability ensure drinking and irrigation water throughout the year mandate the utilization of different technologies for rainwater storage, to be used when necessary. Desert regions characterized by intense rainstorms and high evaporation losses impose a necessity to construct some water structures for storing this water either on the land surface or underground.Surface water storage is implemented via spreading the water on the largest possible pasture areas, or storing it behind dams to be used irrigating forage crops. In fact, the climate prevailing in the West Asia region requires that its countries achieve the optimum use of all water resources by all possible means. The agricultural catchment pond technology is particularly suited for regions with high rainfall rates, and for productive water sources that exceed water requirements in some seasons and are insufficient in other seasons. It also is suitable for areas in which several farms utilize the same water resource. Advantages The advantages of this technology are as follows:
Disadvantages The disadvantages of this technology are as follows:
Cultural Acceptance All types of runoff water harvesting technologies are considered acceptable to the local populations.Because they facilitate the expansion of agricultural activities and livestock breeding, they contribute to increasing the income levels of the settlement populations. They also do not require high technical expertise for their operation or maintenance. Further Development of the Technology Further research was conducted to develop and make these technologies more effective. Various objectives of these research projects include the following:
Information Sources Contacts Aly Al-Quesy Abdel-Naby Fardous Abdel-Aziz Al-Terbaq Abdel-Rahman Al-Tamimy George Somy Mohammed Said Al-Hamidy Mohammed Abu-Haqt Marawan Haddad Noaman Farid Palestinian Ministry of Agriculture References Abdel-Karim Al-Fasil and Abbad Mohamed Al-a’nsy. 1999. Yemen Country Report, Project for the preparation of the Source Book for Alternative Technologies for Freshwater Augmentation in the West Asia Region. Internal Technical Report, ACSAD, Damascus. Abd-Razzaq and Abu Saleh. 1991. Irrigation ponds in Ghore region. Technical report, Rural Research Center, Nablus, An-Najah University. ACSAD. 1983. Analysis and development of the Arab water technologies. Country reports. ACSAD and UNESCO. 1985. Main regional project for the optimum use and maintenance of water resources in rural areas in the Arab countries, concentrating on the conventional water systems.ACSAD, Damascus, Syria.370 p. ACSAD-IFAD. 1997. Scientific work circular on rainwater harvesting and supplemental irrigation for arid and semi-arid regions in the Arab World. ACSAD, Damascus, Syria. FAO. 1989. Guidelines for designing and evaluating surface irrigation system. 45,137 p. FAO. 1991. Water harvesting - Annual for the design and construction of water harvesting schemes for plant production. AGL/MISC/17/91. FAO. 1994. Water harvesting for improved agricultural production. Proceedings, FAO Expert Consultation, November, 1993, Cairo, Egypt.424 p. Haddad, M. 1994. A survey of rainwater harvesting in Palestine. Technical report, Palestine Consultancy Group (East Jerusalem) and IDRC-Canada and University of Ottawa. Haddad, M. 1999. Palestine Country Report, Project for the preparation of the Source Book for Alternative Technologies for Freshwater Augmentation in the West Asia Region.Internal Technical Report, ACSAD, Damascus. ICARD. 1987. Supplemental irrigation in the Near East and North Africa. In: Perriet and Salikini (eds), Workshop Proceedings, Regional Consultation on Supplemental Irrigation, ICARDA and FAO, December 1987, Rabat, Morocco, Kluwer Academic Publishers.911 p. Majed A. 1994. Information on rain catchment cisterns in Hebron district. Personal communication, University Graduate Union, Hebron. Salem Abdullah Baqhezel, Ibrahim Ahmad Said and Mohamed Salem ben-Gouth.1996. Documentary study on examples of conventional irrigation systems and water harvesting methods in Hadramout and Shbouh governorates.Environmental Protection Council, Aden, Ministry Cabinet.
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