The manual is intended to provide the user with sufficient information to understand basically the operation, application, and limitations of the following models: 1) Dynamic water quality model for the Galveston Bay system 2) Densimetric model for the upper Houston Ship Channel 3) HSC and HSC/Zone model 4) Hydroscience model 5) BOD-DO model. However, this manual is not intended to be a detailed user's information source; rather its purpose is to document as much as possible the modeling work on these Galveston Bay Project models.