Negarim

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Description

INTRODUCTION

Negarim is an intervention that consists of small runoff microbasins characterized by a diamond shape, bounded by low earth bunds. This water harvesting technique is mainly used for growing trees and bushes in arid and semi-arid areas but, as side effect, it also preserves soil from erosion. It works great with rainfall rates starting from 150 mm/y and they are applied on slopes up to 15%. This technique is more suitable for small scale tree-planted areas and is pretty easy to create. Since Negarim mostly targets tree- and bush-planting, the area, in which this technique is performed, should be characterized by a soil depth of at least 1.5 meter, but preferably 2m. This is in order to ensure enough space for the roots to develop and for adequate storage of the water harvested.

MECHANISM

Water runoff infiltrates at the lowest tip of each rhombus, where the trees are planted at the infiltration pit. The surface of each basin functions as a catchment area for this infiltration pit. The size of every pit can vary according to plants’ water requirements but usually microcatchment size can vary between 10 m2 to 100 m2 depending on the tree species that has to be planted and on how many are meant to be planted per surface. Negarim interventions are usually done by hand, because it’s hard to mechanize the process once trees are already present.

OTHER

The technique has originally been developed in the Negev desert in Israel; in fact the word Negarim comes from “Neger”, the Hebrew word for runoff. Nonetheless, the first report of this water harvesting technique comes from the south of Tunisia. This microcatchment system is widely spread in Israel, especially among research farms in the Negev desert where the yearly amount of rainfall reaches 100-150 mm. However, Negarim and its variations are well known, and used also, in other arid and semi-arid areas like in North- and Sub-Saharan Africa.

Additional information

Rainfall

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Slope