A sand dam is a rainwater harvesting structure that is built across seasonal river bends in arid and semiarid regions.
The structures are made of a structural wall that traps the sand from water flowing downstream, a shallow well which is fitted with a hand pumped a network of an underground infiltration system.
While the structure utilizes natural filtration processes to yield clean, HEALTHY water, an infiltration system is usually put in place to facilitate the flow of the harvested water into the shallow well, from where it is drawn by use of a hand pump.
Usually, a sand dam will take 2-3 seasons to mature(hold maximum amount of sand) depending on the size of the dam, and amount of rain received in that region. But upon maturation, a sand dam can hold between 2-20 million litres of water at any given time, and amount of water that is able to quench the needs of hundreds of community members and their livestock through out the year.
In many sand dams, the water is enough to even support numerous irrigation farming projects, thus boosting food security and providing employment to SCORES in the rain starved regions.
The ASDF is further improving the utilization of these innovative structures by fitting them with a sump (a large underground tank that stores the harvested water) and a solar powered distribution system that pipes the water to people’s homes or to a point closer to their settlements.
What does a sand dam look like.
How sand dams work.
How is a sand dam constructed.
The sand dam structure(wall) is made of two basic parts,the spill way,and the two wings at each side.However, the dam may also require side protection walls and an apron depending on the nature of the soil at the site.
While the wall reduces the downstream speed of the water inorder to collect and hold the sand,it also consists of a spill way which ensures the water continues to flow down stream,in natures own course.
The wings add to the general ROBUSTNESS if the dam,while at the same time concentrating the flow into the normal river channel so as to avoid side spillage and pos
The sible encircumventing of the river around the dam walls.
The Apron and the side protection walls are sometimes necessary to prevent erosion around the dam walls.
After sand dams have harvested the water, the water can be drown through a number of ways.
1.traditional scoop holes.
With the water nearer the surface,communities can now draw clean,sufficient water from the traditional scoop whole with a lot more ease than it used to be before the sand dams were constructed.
Along with the Sand dam,ASDF supports the community with the construction of the shallow well which is then fitted with a hand pump for easier access of the water.
3.Solar pumping system
In some sand dams,we have been asssting the community access the harvested water a lot more conveniently by installing solar powered water pump which pipes the water to more central poits and much closer to the beneficiary homes.
What sand dams don’t do.
- Prevent the flow of water downstream
- hold or encourage siltation
- change the rivers natural cause
- risk flooding to sorrounding region
how is the sand dam technology more superior than other wh technologoies?
- Are cost effective - they keep the water where its needed
- Help in the reclamation of eroded land
- Are low maintenance
- Impact increases as they mature
- Raise the water table around them
Sand dam water is not only accessible.its clean, its safe.