ABSTRACT
The availability of fresh water is an issue as old as civilizations. Across the ages, cities thrived where the supply of potable water was abundant and collapsed in the face of drought. Today, mankind uses about 4000 km3 water/year for domestic/industrial use, and 14,000 km3/year for agriculture and grazing lands (Oki and Kanae, 2006). These withdrawals account for less than 10 and 30 percent, respectively, of the world’s renewable fresh water resource, which indicates that, if the water cycle is maintained wisely, fresh water can cover human demand far into the future (Oki and Kanae, 2006). The uneven spatial and temporal variability of fresh water, however, results in 2.4 billion people currently living in water-scarce environments. The rapid and often irreversible changes which follow urbanization may further enhance such inequity.
