Industry uses water throughout the energy supply chains. The purpose and scope of this book is to describe water for the cooling needs of thermoelectric, or steam cycle, power plants. The book focuses on engineering fundamentals along with environmental and economic contexts. Water is an excellent heat transfer medium, and it has historically been abundant and cheap. Thus, thermoelectric, or thermal or steam-electric, power plant cooling needs are usually served by withdrawing and consuming fresh and saline water. Thermal power plants do not have to use water for cooling, but if the desired quantities of water are available, then water-cooling systems are the most economic.