The standard WASP7 eutrophication module includes nitrogen and phosphorus cycling, dissolved oxygen-organic matter interactions, and phytoplankton kinetics. In many shallow streams and rivers, however, the attached algae (benthic algae, or periphyton, attached to submerged substrates) are often of greater importance than phytoplankton. These attached plants affect water quality in various ways, and their impact must often be considered in order to properly evaluate riverine water quality conditions. An advanced WASP7 eutrophication module has been developed to handle streams and rivers with bottom algae. This supplemental user manual documents the new bottom algae algorithms, including the kinetic equations, the additional model input and output, and a series of model verification tests.