The Use of Water Quality Models in Management Decision Making

The use of water quality models in three management contexts is described: screening, planning, and design. Screening models are illustrated by describing a methodology applicable to large areas of land and another applied to a large number of chemicals. The application of models in a planning context is illustrated by a local planning agency9s use in developing nonpoint source control strategies and by the federal government9s use in assessing potential exposure to a pesticide. Development of design criteria is illustrated by summarizing the long history of model use to develop effluent limits in the Holston River basin (Tennessee).