Freshwater is essential to life on Earth and is a vital input to almost every productive human activity. As described in Chapter 2, water scarcity is increasing globally. Today, hundreds of millions of people do not have access to safe supplies of potable water. Climate change is expected to exacerbate water scarcity over the coming decades, adding to the pressure on resources and increasing potential for conflict between competing users. Past failures to recognize the true value of water have and continue to lead to misallocation and wasteful use of our dwindling supplies.