Excessive eutrophication is a major water quality issue in lakes and reservoirs worldwide. This
complex biological process can lead to serious water quality problems. Although it can be adequately
addressed by applying sophisticated mathematical models, the application of these tools in a
reservoir management context requires significant amounts of data and large computation times.
This work presents a simple primary production model and a calibration procedure that can
efficiently be used in operational reservoir management frameworks. It considers four state
variables: herbivorous zooplankton, algae (measured as chlorophyll-a pigment), phosphorous and
nitrogen. The model was applied to a set of Portuguese reservoirs. We apply the model to 23
Portuguese reservoirs in two different calibration settings. This research work presents the results of
the estimation of model parameters.