Arid and semi-arid regions can be defined as environments in which water is the limit ing factor for bio-systems. This means that survival of life in these regions involves a constant struggle to obtain this limited commodity and draw the maximum benefit out of it. However, despite the difficulties for plants, animals, and man to live in, these regions, they are being utilized more and more because of the pressure of world population growth. This is expressed in the expansion of agricultural activities in desert lands as well as by the formation and rapid growth of urban and industrial...