High quality water is more than the dream of the conservationists, more than a political slogan; high quality water, in the right quantity at the right place at the right time, is essential to health, recreation, and economic growth. Of all our planet's activities - geological movements, the reproduction and decay of biota, and even the disruptive propensities of certain species (elephants and humans come to mind) - no force is greater than the hydrologic cycle.