This article explores how scientific and engineering principles are inexorably linked to the regulation of water. Scientists and engineers first discovered the link between disease and water sources in the mid-19th century. Over the years, scientists and engineers have led the way to identifying water quality problems and their causes. These discoveries have directly contributed to the scope of water regulation in the United States and elsewhere. In addition, changes in water quality regulation have dictated the need for increasingly sophisticated water treatment technologies and engineers have been at the forefront of the development of these water control technologies. This session will discuss the historical roots, and the development over the century, of scientific principles and engineering technology in identifying and combating water pollution. It will also provide a solid foundation for understanding current efforts underway to solve current and future water quality issues.