Water and energy are inextricably linked and mutually dependent, with each affecting the others availability. Since 2009, the Government Accountability Office (GAO) has issued five reports on the interdependencies between energy and water. These reports have shown that a considerable amount of water is used to cool thermoelectric power plants, grow feedstocks and produce biofuels, and extract oil and natural gas. Some of these sources of energy may also negatively affect water quality. In addition, developing oil and gas resources can product waste-water, known as 'produced water', that must be managed or treated. Conversely, significant amounts of energy are needed to extract, transport, treat, and use water in urban areas. This book identifies key energy-water nexus issues that Congress and federal agencies need to consider when developing and implementing national policies for energy and water resources.