I was up in Tete, Mozambique last week scoping out sand dams. They were pretty cool. You take a seasonal riverbed, build a dam at a prominent point where the river narrows and then opens again; then when the rains come, the water soaks deep into the sand acting as a reservoir. The sand itself is a natural filter for bacteria and water-borne disease agents. A pipe can be placed at the bottom of the dam, capped, and used for drinking water year round. You can also dig a hole in the sand at the surface, without digging too far, and up comes water. Its a sustainable clean water source for communities, their livestock, and agriculture. Very little maintenance and low-cost to build. We're hoping to pilot a few through our Moz office this next year.
Take a look!