A multiconstituent moving segment model for water quality predictions in steep and shallow streams

The Segment Travel River Ecosystem Autograph Model (STREAM), which is a multiconstituent stream ecosystem model, was developed and applied to steep and shallow streams in this study. The formulation of STREAM was based on the moving segment approach in the cell-in-series (CIS) system where a stream is assumed to be a series of completely mixed flow reactors. Major constituents included in STREAM are dissolved oxygen (DO), 5-day biochemical oxygen demand (BOD₅), suspended solids (SS), coliform bacteria, nitrogen species, phosphorus species, and phytoplankton. Dissolved oxygen change caused by sediment oxygen demand (SOD) and respiration and photosynthesis of periphyton and macrophytes are included in the model structure. STREAM was programmed in BASIC and can be executed on an MS-DOS personal computer. STREAM was designed for implementation with EGA/VGA colour graphics. The model results and the data are displayed on the computer screen and the output device in a graphic format. A demonstration application is presented to validate the STREAM model. The results indicate that the STREAM model could effectively simulate water quality of steep and shallow streams where longitudinal dispersive transport is negligible.