We’d like to believe there’s an infinite supply of water on the planet. But the assumption is tragically false. Available fresh water amounts to less than one-half of 1 percent of all the water on earth. The rest is sea water, or is frozen in the polar ice. Fresh water is renewable only by rainfall, at the rate of 40,000 to 50,000 cubic kilometers per year. Due to intensive urbanization, deforestation, water diversion and industrial farming, however, with the drying of the earth’s surface, even this small finite source of fresh water is disappearing; if present trends persist, the water in all river basins on every continent could steadily be depleted.