Modeling Short and Longterm Effects of a Thermal Plume on Indigenous Fish Populations

An innovative biothermal modeling approach to evaluate the effects of heat load from a power plant on resident fish and shellfish species is described. The assessment links several biological functions (growth, reproduction, avoidance, migratory blockage and thermal mortality) to hydrothermal simulations of the plant's thermal plume under different plant operating scenarios. Species-specific temperature tolerance polygons that incorporate information on the thermal tolerance regimes for the biological metrics as a function of acclimation temperature were developed. Combining this information with hydrothermal modeling results detailing the spatial and temporal characteristics of a thermal plume, the biothermal model provides an estimate of effects of the thermal discharge in terms of percentage changes in the important biological metrics, thus providing a quantitative evaluation of the effect of the plume on the balanced indigenous fish community. Integration of the results of this approach with density-dependent models to project long term effects on fish populations due to thermal effects such as habitat loss and changes in growth rates is also discussed. Limitations of the model and potential future refinements to address additional biological effects are discussed and evaluated.