Demi-lunes / semi circular bunds

Category:

Description

INTRODUCTION

The technique of creating Demi-lunes belongs to the overall category of water harvesting interventions and consists of half-moon shaped basins dug in earth. The main goal of water harvesting, as the name  suggests, is to collect water, and to make moisture available for vegetation for a longer time. This type of microcatchment water harvesting technique is suitable for slopes up to 15%, however bunds made of earth are seldom used in areas with slopes greater than 5% with a  precipitation rate higher than 300 mm/y. At lesser slopes, Demi-lunes are also used in areas with higher rain falls.

MECHANISM

Bunds are created by using earth or stones and have a diameter from 2 to 8 meter (although they can measure up to 12m). The bund tips are usually placed on a contour line, facing upslope. Bunds are usually 30-50 cm high. They are arranged in alternating patterns so that the line below can catch the runoff coming from the line above, and so on. In dry conditions, bunds diameter is bigger, whereas, in wetter conditions, bunds are usually smaller but more copious.

OTHER

The space between the bunds can vary according to the purpose. Larger and more widely spaced Demi-lunes are more suitable for grazing land rehabilitation or fodder production. Smaller and closely spaced half-moons fit better for growing trees and shrubs.

A great example of the effect of Demi-lunes over time has been recorded in Kuku, Kenya by Justdiggit, an NGO working on ecosystem restoration, during the rainy and dry season 2017-2018

Additional information

Rainfall

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Slope

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Land use

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Stones

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