A liman is an earthwork that collects floodwater by means of a dam in a gully or riverbed. Trees are planted in the flooded area of the dam. An overflow channel regulates the level of water accumulated and allows the excess to escape.
Overflow channel next to the liman. Photo: KKL-JNF Photo Archive
This forestry method is based on the principles of runoff farming, in which water is collected from the runoff area (i.e., the catchment area) by artificial means (a ramp, terrace, hole, etc.) in such as way as to allow it to permeate the soil in the run-on area. The ground in the runoff area is relatively impermeable as compared with that in the run-on area, where the water penetrates the soil with much greater ease.
The limans are, indeed, a remarkable example of floodwater harvesting, which is a system based upon the collection of water from ephemeral or permanent streambeds within a comparatively large catchment area. In other parts of the world this method is used to augment and protect harvests, improve grazing land, accelerate tree growth in forested areas, prevent soil erosion, combat salinization of the soil and enrich groundwater. Although there are a number of different types of liman in the Negev, all of them operate in accordance with the same basic principles. The most common form is the streambed liman.
The limans’ microclimate
A liman ecosystem. Photo: KKL-JNF Photo Archive
Because of the trees’ well-developed canopy the sun’s radiation within the area of the liman is considerably lower than in the exposed surrounding environment. As a result (and despite the fact that measurements show no significant average temperature or humidity differences between the two), heat stress levels within the liman are markedly lower than in the exposed desert. In summertime people feel much more comfortable inside a liman than in the area around it. This means that in the summer months the liman provides travelers in the Negev with a high quality low-heat-stress area for rest and recreation in natural surroundings.
In wintertime the shade of the eucalyptus trees with which the limans are planted creates a chillier environment than that of the surrounding desert, and this may be too cold for comfort. Because of this, the possibility of planting deciduous trees alongside evergreens should be considered.
Purposes of the Negev Limans
The hundreds of limans found throughout the Negev serve the following purposes:
- The provision of shady roadside havens for the benefit of tourists and holidaymakers.
- The provision of shaded areas where soldiers on training exercises can stop and rest.
- Improving the roadside landscape throughout the Negev.
- The provision of grass and shade for flocks grazing in the area.