Managing Scarce Water Resources in Agriculture in West Asia and North Africa - Restorative Redevelopment of Devastated Ecocultural Landscapes - page 451

efficiently until another resource becomes limiting. Since water is often the most
limiting resource, any improvement in water RUE will necessarily lead to enhanced
use of other resources. From the perspective of a national economy, a key goal for
water use productivity is to improve net economic returns per dollar invested in
water use, favoring investment in the urban and industrial sectors. However, such a
view fails to adequately recognize the social and environmental benefits from using
water in agriculture.
The use and definition of water use efficiency and/or water productivity terms is
still controversial. FAO relates water use efficiency to the level of performance of
irrigation systems from the source to the crop and defines it as the ratio between
estimated plant requirements and the actual water withdrawal (FAO 2003b). This
definition is more or less closer to the classical irrigation efficiency. On average,
this water use efficiency in the developing countries is estimated, by FAO, to be
around 38%. FAO considers that improving irrigation efficiency is a slow and dif-
ficult and site specific process that largely depends on the local water scarcity
situation. It may be expensive and requires willingness, know-how, and actions
at various levels. Technology permits accurate water application to crops in the
optimum quantity and timing. The application of advanced technology, however,
depends on the investment and capacity as well as an economic incentive to make
it worthwhile.
It should not be surprising that water use efficiency and water productivity
issues make only slow progress and draw little attention whenever water is cheap
(or highly subsidized), plentiful (such as in Latin America), or it has no other
user to compete on. Among the serious causes for current inefficient use of water
in most countries are that water interest, use, control, monitoring, and manage-
ment are divided among many governmental and nongovernmental agencies, divi-
sions, and bodies, simply because it has multiple uses that concern a wide range
of disciplines and interests. There is lack of coordination and harmony among
these divisions. There are numerous forces involved ranging from individuals to
administration, political, and economics. This of course creates great difficulties
in obtaining data and in improving the use and management of water resources.
The increasing pressure and competition on water should bring a new and com-
prehensive and integrated approach to improve the current management of water
resources .
RESPONSES TO IMPROVE WATER PRODUCTIVITY
d efiCit i irrigation
When water is limiting irrigation, the rules of scheduling should be modified for
improved water productivity. In intensive irrigation development, all efforts includ-
ing research and advancement in technology development are geared towards achiev-
ing maximized yield per unit of land. However, in water-scarce areas, water, not
land, is the most limiting factor to improved agricultural production. Accordingly,
maximized yield per unit water (water productivity or water use efficiency), and
not yield per unit of land, is a more viable objective for on-farm water management