Imagine that you live in a place that receives rain only during certain months of the year. During the rest of the year, you spend up to eight hours per day walking to a remote water source to fetch water for your family. To make matters worse, the water you spend all day collecting is likely contaminated with water-borne microorganisms that will make your family sick.
Enter sand dams. These simple but ingenious structures allow communities in semi-arid places harvest and store the rain they receive during the rainy season to be used year-round for drinking and farming.
Sand dams are simple, reinforced concrete walls that are built across the beds of seasonal rivers—rivers that contain water during the rainy season but are dry the rest of the year. During each rainy season, water and sand accumulate behind the dam. By the end of three rainy seasons, the dam is completely filled with sand; however, it is also filled with water—up to 20 million liters of it—which is a year-round supply for up to 1,000 people.
The sand in a sand dam affects the water in three different ways: covers it to prevent it from evaporating or being contaminated; filters it to remove impurities; and, acting as a natural sponge, allows the surrounding land to retain water, allowing trees and other plants to grow.
Water is drawn out of the dam either through traditional scoop holes, or pumped out and used for drinking and crop irrigation.
Along with being cost-effective, sand dams are fairly simple to construct. They also last at least 30 to 50 years and have virtually zero operation and maintenance costs.
Read more about sand dams on The Water Project website.