Semicircular bund

A semi-circular bund (also known as a demi-lune or half-moon) is a rainwater harvesting technique consisting in digging semilunar holes in the ground with the opening perpendicular to the flow of water.

Background
These holes are oriented against the slope of the ground, generating a small dike in the curved area with the soil from the hole itself, so they capture the rainwater running downhills.

These structures allow water to seep into the soil, retaining in the subsoil a greater amount of moisture. But also, it prevents the loss of fertile soil.

Semi-circular bunds are used to reforest arid zones with irregular rain patterns, allowing the growth of plants and trees, such as in the Sahel.