Functions of a sand storage dam

The primary function of a sand dam is increasing the water availability by storing water in the riverbed and -banks. Water is stored in the spaces (voids) in the sand, which can hold up to 35 percent of the volume of sand. Sand dams obstruct groundwater flow through the riverbed, resulting in a (continuous replenishment of the) enlarged groundwater reservoir upstream of the dam.

Besides this, sand dams can have other functions and positive side effects, like:
1. Regional groundwater recharge
A cascade of sand dams in a will cause a general rise in groundwater levels in a larger area. This positively affects the environment in the surrounding area of the dam, due to more water availability for people and vegetation.
2. Sand harvesting and rehabilitating of gullies
Sand dams can rehabilitate erosion gullies, while the sand sediments behind the dam can be harvested for sale. If a sand storage dam is built for this purpose, the dam doesn’t have to be impermeable. Usage of plastic bags filled with soil is more profitable for this purpose (Nissen-Petersen, 2006).