Description
Similar names: diamond-shaped micro catchment, V-shaped micro catchment, V-shaped bunds, Triangular bunds, small run-off basins
Negarim is an intervention that consists of small runoff micro basins characterised by a diamond shape, bound by low earth bundles. This water harvesting technique is mainly used for growing trees and bushes in arid and semi-arid areas but, as a side effect, it also preserves soil from erosion. It works great with rainfall rates starting from 150 mm/y and can be applied on slopes of 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 characterised by a soil depth of at least 1.5 metres, but preferably 2m. This is to ensure enough space for the roots to develop and for adequate storage of the water harvested.
The technique was originally 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.
PRE-CONDITIONS FOR IMPLEMENTATION
- It is important to point out that it is not possible to grow trees where the biophysical conditions do not allow it (such as too shallow soils).
- Maintenance is required to repair damaged bunds; the site should be inspected after each heavy rainfall and any breakages must be repaired.
- Negarim interventions are usually done by hand because it is hard to mechanize the process once trees are already present.
- Soil type: Knowing the soil texture is fundamental to understanding and to designing successful micro catchment systems. Micro catchments on clay soils with medium to fine texture are the best to generate sufficient runoff, hence not subject to erosion.
- Soils that should be avoided: those that present cracks on drying, such as those , containing a high proportion of clay. very sandy soils or soils with poor structure should also be avoided.
- Adding mulch and organic matter: Adding these features in the basin area significantly increases the success in retaining water and improves soil fertility. However, if mulching is too expensive, it should be combined with grass strips or tree strips.
METHOD OF APPLICATION
Material required
- Line level or water tube to define the contour line
- Tape measure
- String or thin rope
- Peg
- Hoe (not strictly necessary)
- Shovel
Steps of Implementation
1. Building infiltration pit: 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. This depends on the tree species that have to be planted and on how many are meant to be planted over the surface area. A 3 x 3 m spacing is the minimum required for a Negarim catchment system.
2. Choosing the Negarim design: Sometimes V-shaped Negarims are more efficient than those that are diamond-shaped, as the excess water can flow around the tips of the bund and reach the other V-shaped Negarims (a bit like as seen with demi-lunes), but water storage capacity will be less. V-shaped Negarims are particularly useful when implemented where there are a small number of trees present around homesteads
Diamond shaped:
Seedlings in the pits:
V-shaped:
3. Choosing plant species: Plant species that can endure periods of intermittently wet or dry soil will benefit most from these kinds of interventions. These plants should have deep roots and be well accustomed to local rainfall patterns. Tree seedlings of at least 30 cm in height should be planted after the first rain of the season. It is recommended to plant two types of seedlings: one in the bottom of the pit and one on a step at the back of the pit. If both survive, remove the weaker one at the beginning of the second season. Some species can be planted directly.
Click here for a detailed step-by-step on how to build Negarim microcatchments.
BENEFITS
This intervention contributes to:
CASE STUDIES
1. Negarim application in citrus plantation in Nigeria
Description
The project discussed is about setting up a system called Negarim Micro-catchment to grow citrus fruits in Nigeria. This system is designed to collect rainwater for watering the trees and preventing soil erosion. Water harvesting, which is collecting rainwater for later use, is essential for areas with little rainfall, like Nigeria. For this project, a location in Kwara State was chosen, and materials like soil and stones were used for construction. Soil is used to build bunds, which are like small walls or barriers, while stones are used for pitching, which is arranging them to prevent erosion. It's important to choose the right kind of soil that doesn't crack when it dries out and can hold its shape well. Stones are used strategically to reinforce the structure and make it more durable. These materials are chosen because they're easily available locally, and using them helps keep the costs down. Plus, they're effective for preventing soil erosion and collecting rainwater for the citrus trees. Factors like rainfall, soil quality, and land slope were considered during planning. Various tests were conducted to determine water requirements, soil characteristics, and rainfall patterns. The findings showed that the soil is suitable for plant growth, and there is sufficient rainfall for the citrus trees. Overall, the project aims to improve citrus fruit cultivation by harnessing rainwater and maintaining soil health.
2. Negarim application in a mango plantation in Kenya
Description
The study conducted in Mbeere District, Kenya, aimed to evaluate different water harvesting techniques for establishing improved mango varieties on smallholder farms. The area faces challenges like low and erratic rainfall, which affects tree survival. Researchers tested two microcatchment systems (V-shaped and diamond-shaped) alongside conventional planting holes. They found that despite drought conditions, mango seedling survival was high (>70%) due to farmers' innovative techniques like watering and mulching. Farmers preferred the V-shaped microcatchment for its effectiveness in moisture retention and labor requirements. Overall, the study highlights the importance of farmer participation in technology modification and the potential of water harvesting techniques like the Negarim system to improve tree survival and agricultural productivity in semi-arid regions like Mbeere District, Kenya.
