You are here:
WASP7 BENTHIC ALGAE - MODEL THEORY AND USER'S GUIDE
Citation:
AMBROSE, R. B., J. L. MARTIN, AND T. A. WOOL. WASP7 BENTHIC ALGAE - MODEL THEORY AND USER'S GUIDE. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-06/106 (NTIS PB2007-100139), 2006.
Impact/Purpose:
Improve the scientific understanding of the processes controlling nutrient distributions in surface waters. Produce a suite of enhanced models for characterizing nutrient distributions in surface waters by incorporating improved process understanding in existing models (e.g., WASP), by developing new models (e.g., WHAM, reactive transport), and improving linkages between model components.
Description:
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. This advanced WASP7 module, named "periphyton," includes the standard WASP7 eutrophication algorithms, and incorporates bottom algae, with three additional state variables: bottom algal biomass, bottom algal cell nitrogen, and bottom algal cell phosphorus. Bottom algae are not subject to advective and dispersive transport. Sources and sinks include nutrient uptake, growth, nutrient excretion, death, and respiration. Nutrient uptake rates are driven by concentrations of inorganic nitrogen and phosphorus in the water column and within algal cells, and are controlled by cell minimum and half-saturation parameters. Biomass growth is computed from a maximum zero or first-order rate constant that is adjusted internally by water temperature, bottom light intensity, internal nutrient concentrations, and maximum carrying capacity. Nutrient excretion, death, and respiration are represented by first-order, temperature dependent rates. Growth, respiration, and death rates affect other model state variables, including dissolved oxygen and nutrients. The algorithms for predicting bottom algal biomass and nutrient concentrations are based upon the periphyton routines included in the QUAL2K model (Chapra 2005).