University of California Water Resources Center

An ecological model incorporating benthic algae was developed using an existing unsteady one and two-dimensional water quality model (RMA-4q) to transport constituents in the water column. The types of benthic algae simulated are attached filamentous algae (e.g. Cladophora) and perilithic biofilm. These are influenced by different physical processes, although hydrodynamic detachment occurs with each. Attached filamentous algae occur in the turbulent flow region and access to nutrients is assumed not to be limited by diffusion, as is the case for perilithic biofilms. The biofilrn equation solution is therefore more difficult to solve. The theoretical development of the equations for each benthic algal type is presented, along with numerical solution schemes. Field data collection methods and their results are discussed. The data are used in support of the modeling effort. Finally, results from an example application for the Russian River are given. The effect of nutrient loading and hydrodynamic detachment are evident. Problems with temperature and its relation to system geometry are discussed. Topics for future research are presented.