Managing Scarce Water Resources in Agriculture in West Asia and North Africa - Restorative Redevelopment of Devastated Ecocultural Landscapes - page 467

It is ideal when labor is not available or when it is costly. Operating cost is around
US$100/ha, including planting. Shrubs planted in the semicircular bunds showed a
survival rate of over 90 percent, compared to 10 percent without water harvesting.
They survived three consecutive years of drought and supported local community
with grazing in most difficult times. Currently only less than 10 percent of the rain-
water is utilized in transpiration. By microcatchment beneficial rainwater can be
increased to 60 percent and with macrocatchment to 40 percent.
Contour-bench terraces microcatchment WH are constructed on very steep slopes
to combine soil and water conservation with water-harvesting techniques. Cropping
terraces are usually built level and supported by stone walls to slow down the flow
of water and control erosion. They are frequently used to grow trees and bushes, but
rarely used for field crops. The historic bench terraces in Yemen are a good example
of this system. Since they are constructed on steep mountainsides, most of the work
is done by manual labor.
Rooftop water harvesting collects and stores rainwater from the roofs of houses,
large buildings, greenhouses, courtyards, and similar impermeable surfaces, includ-
ing roads. Most of the rain can be collected and stored. How the harvested water will
be used depends on the type of surface used and how clean it is, as well as users'
needs. Such systems provide a low-cost water supply for humans and animals in
remote areas. Although mainly used for domestic purposes, this technique also has
agricultural uses.
There are, however, several limitations to widespread use of water harvesting in
the region. Among the most important are the appropriate selection of site, method,
and crop; the design, data, and engineering work; the precision in implementation;
the integration with other components of the system; and the annual maintenance.
One of the greatest limitations to adopting water harvesting works is the lack of
clear land ownership, which can be public, tribal, or other forms. Changes are
required to provide incentive for people to invest in this promising water manage-
ment intervention.
Direct benefits of water harvesting are not high. Most of the benefits are envi-
ronmental and social. Farmers get only small portion of the total benefits and this
may not be attractive for investment. The public shares the benefits in improved
environment, less migration, and social stability, and this requires that they also
share the cost. It is vital that users are involved from the planning stage of devel-
opment. Institutions should be strengthened and integrated watershed management
approaches should be used to resolve upstream-downstream conflicts.
WP i mProvement and the e nvironment
Now, it has been globally understood and accepted that environment is a water using
sector, which is strongly linked to the sustainability of water resources development
and management. This is a complex issue for both rich and poor countries. It is tech-
nically challenging and often entails difficult trade-off among social, economic, and
political considerations. One of the important achievements in the water resources
issue in recent years is the clear and firm inclusion of environmental water require-