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Water harvesting using sandbox dams
2022-12-11
Dr. Atheer Saleem Obaid Al-Mawla
Upper Euphrates Basin Developing Centre –University of Anbar
Water resources are one of the most important criteria for building and developing societies, as planning and management of water resources has become today one of the most important topics in human life, especially in arid and semi-arid areas such as the Iraqi Western Desert, where rainfall is usually very limited and spatially distributed.
For example, the evaporation losses from the surfaces of lakes in southern Iraq, which have an area of about (9000 km2), exceed (27 x 109 m3). As for the reservoirs of small dams, where the surface area is usually small and does not exceed a few kilometers, the evaporation losses amount to about 75% of the total annual storage of these dams, which are characterized by being at small depths, as the annual loss of evaporation depth of these dams is about (2.25-3) meters (Kamel, 1999), this depth stores the highest percentage of the reservoir volume of these dams. For example, if the surface area of a small dam is one kilometer, the annual evaporation loss of this dam is about (3 x 106 m3). (Alabaid, 2008) .
Increasing demand for water requires more water storage in times of water abundance, such as in November of this year, which was characterized by abundant rainfall to be used in times of need. However, dams can lose very large amounts of their storage due to evaporation, as mentioned earlier.
Attention and efforts are directed towards subsurface storage to reduce evaporation losses on the one hand and to maintain water quality on the other. One of the newly proposed methods of subsurface storage is water storage in so-called sand storge dams, which are small concrete interceptor dams built at the bottom of the valley perpendicular to the direction of flow (Figure 1). (The sand accumulated at the front of these dams is of large grain diameters, and thus natural aquifer is recharged, resulting in the formation of an aquifer at the front of the sand dam. During the dry season, the manually stored groundwater is extracted by shovel drilling (hand-drilled wells on the river bed) as was the case thousands of years ago in arid and semi-arid areas and wells can be drilled. During short rainy seasons, rain torrents are used and surface water instead of groundwater for various purposes. Hoogmoed 2007)).
The technique of sand reservoir dams is a very ancient technique as it is said that the Babylonians first used it more than 4,000 years ago. In the Kitui region, such dams were built during the fifties and sixties by various organizations. The method has been applied in many places around the world for long periods. For example, groundwater storage structures have been found on the island of Sardinia in Italy, where dams were built in Roman times and in Tunisia and North Africa dams of about the same age have also been found. (Van Haveren 2004).
These dams have proven highly effective in storing water by reducing losses as well as maintaining water quality, so this technology can be used in the western region of Iraq.
Resources:
1- Kamel, Ammar H., 1999 evaluation runoff volume in Iraqi western desert by synthetic unit hydrograph, Baghdad
2- Alabaid, Abd-alwhhabIktaier, 2008, "the correlation between desert plugging and ground treasurers is economic necessity", University of Anbar, center of desert studies
3- Hoogmoed, Merel. 2007 Analyses of impacts of a sand storage dam on groundwater flow and storage - Groundwater flow modeling in Kitui District, Kenya, Kitui District, Kenya Master thesis Hydrogeology code 450122, 27 ECTS.
4- Haveren, B.P. van, 2004, Dependable water supplies from valley alluvium in arid regions, Environmental Monitoring and Assessment 99: 259 – 266 pp
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