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[[Image:94px-Icon_sanddam.png|right]]

Sand dams are a simple, low cost and low maintenance, replicable rainwater harvesting technology. They provide a clean, local water supply for domestic and farming use and are suited to semi-arid areas of the world.

==Suitable conditions ==

Sand dams can be constructed and used for household, community and even municipal uses. There are examples of sand dams which are connected via infiltration galleries, off-take wells and pump stations into municipal piped water systems.

==Construction, operations and maintenance==

First a trench needs to be dug. Its position is marked out using pegs. Then it is excavated and the soil placed downstream. It can also be dug out into bedrock. It should then be checked for weathering zones and cracks. Round bars are placed vertically along the trench to reinforce it. Then a foundation is laid consisting of 2 layers of cement with barbed wire in between. Once this has set, the trench is filled with masonry or mortar and hardcore. The wing walls and final dam wall can then be constructed. Finally any exposed parts of the construction are plastered.

'''Specific advice'''

* Timing is important: dams should be built during the dry season, but don’t build dams too close to the rains in order to avoid the trench filling up with water or the dam being washed away.

* The method depends on the type of dam and the type of ground. The construction of sand dams in cascades improves total storage and efficiency and minimizes seepage losses. Dams made of concrete, stone-masonry (cheapest and easiest) and brickwork require skilled labour for construction, but are stronger and have a longer lifespan.

After the dam is built, an outlet for water extraction must be constructed for drinking, agriculture, etc. Hand dug scoop holes are the simplest possibility, however the water can easily be contaminated. Covered shallow wells, either with or without [[Handpumps]] or a [[Rope pump]] protect the water much better. It is also possible to construct an outlet pipe with a tap. In certain designs for sand dams, a pipe is shown that takes water by gravity ''through'' the dam wall. These are said to not work well due to either a blocked intake, a broken tap on outlet side and the possibility of weakening the dam wall. Where water is abstracted directly, risk of contamination increases. In such a case, household water treatment should be advocated (e.g. [[Sodis]]). <br>

====Maintenance====