Models and software for reservoir eutrophication assessment

Abstract

Eutrophication has several direct and indirect effects on reservoir water quality and uses. The paper describes assessment procedures recently developed for application to Corps of Engineer reservoirs. Study phases include problem identification, data gathering, data reduction, and model implementation. Three interactive computer programs (FLUX, PROFILE, BATHTUB) assist in the last two phases. Eutrophication-related water quality conditions (expressed in total phosphorus, total nitrogen, particulate phosphorus, and hypolimnetic oxygen depletion rate) are predicted using empirical relationships calibrated and tested for reservoir applications. Based upon research using several independent data sets, previous “northern-lake-based” empirical modeling approaches have been modified to account for effects of (1) nonlinear nutrient sedimentation kinetics; (2) algal growth limitation by phosphorus, nitrogen, light, and flushing rate; (3) inflow nutrient partitioning (bioavailability of dissolved versus particulate loadings); (4) seasonal variations in loadings and morphometry; and (5) spatial variations in nutrients and related trophic-state indicators. To reflect input data limitations and inherent model errors, inputs and outputs can abe expressed in probabilistic terms. The segmented model can be applied to single reservoirs (mixed or spatially segmented), networks of reservoirs (hydrologically linked), or collections of reservoirs (hydrologically independent). The last type of application permits regional comparisons of reservoir conditions, controlling factors, and model performance. © 1986 Taylor and Francis Group, LLC.