Water is integral to life on Earth. It makes up the majority of our cells and the cells of the biota we depend on for life. We harness the power of water as it moves from the atmosphere, subsurface, and oceans, creating energy, using it for cleaning, and transporting ourselves and our things. As a result, people have long managed landscapes and waterscapes to control water and optimize the benefits it provides (Andreassian, 2004). In the context of Earth’s water cycle, however, people affect only a small fraction of the total available water. Liquid freshwater on or near the earth’s surface and in the biosphere, the water that we can manage, is less than 0.3% of all water on the planet (Shiklomanov, 2000). Relatively little water has been created or destroyed since water first appeared on earth; the water cycle moves water among forms and locations (Morbidelli et al., 2000).