Description of Challenge
Traditional water harvesting systems in North Africa and SW Asia, include some of the oldest sustainable methods of water harvesting in arid lands. An understanding of these systems, which have lasted for millennia, is crucial for current efforts to combat desertification and rehabilitate degraded desert habitats. This is at a time when climate change is compounding the threat to many areas in North Africa and SW Asia that are extremely vulnerable to shifts in climatic conditions.Solution
At present there are two main classifications of traditional water harvestng systems: firstly by Oweis et al. (2004), and secondly, by Prinz (1996. 2000).
The classification by Oweis et al. (2004) (see below) starts by subdividing techniques on the basis of the size of the catchment area, which is the area from which water is collected.
Small catchment areas (micro-catchments), are then further classifed as roof-top and on-farm techniques. By contrast, techniques that depend on large catchment areas (macro-catchment), are further subdivided into ‘wadi bed’band ‘off-wadi’ systems.
Prinz bases his classification initially on the basis of the water source, namely, rainwater, floodwater, and groundwater. The current proposed classification follows Prinz in using the source of water as its starting point. However, in the current system a recognition is made of harvesting moisture (dew and air moisture), snow and snow meltwater.
In addition, a differentiation is made between ephemeral wadi water and floodwater from perennial water, such as the Nile. Water from surface runoff is also recognized as a category on its own.
In many cases, harvested water that is not used immediately, is stored for later use in cisterns, reservoirs, tanks, or wells. These storage facilities are often lined to prevent water loss, and may be covered to minimize evaporation and prevent the introduction of unwanted sand or litter.
Similar facilities are used to harvest groundwater. Since they depend on seepage from groundwater, the cavities are mostly unlined. In many cases, water harvesting from, for example, surface runoff, is based on either channeling runoff to storage areas or enhancing infiltration to maximize the amount of moisture in the ground.
Copied from The SHADUF Project web site. The project aims to create a database of traditional techniques and to focus attention on the rich and diverse water harvesting, water irrigation and wastewater-related heritage in the Medit
