ABSTRACT
Before 1972, water pollution control efforts were based on achievement of ambient water quality standards. In 1972, the Federal Water Pollution Control Act was amended to require, at a minimum, a level of control based on available treatment technology. Under this approach, the need to determine impact on the ambient environment was largely eliminated. Water quality modeling technology had advanced significantly and was ready to address a variety of water quality problems. Estuaries are coastal water bodies where freshwater meets the sea. They are traditionally defined as semi-enclosed bodies of water having a free connection with the open sea and within which sea water is measurably diluted with freshwater entering from land drainage. There are a number of reasons that make estuaries an important natural water resource. A number of water quality problems have been observed in estuaries. The chapter also presents an overview on the key concepts discussed in this book.
