A model, targeting eutrophication of stormwater detention ponds was developed and applied to simulate pH, dissolved oxygen and the development of algae and plant biomass in two mature planted wetponds for run off control. The model evaluated algal and plant biomass growth into three groups namely; phytoplankton, benthic algae and macrophytes. The study evaluated large data sets from an intensive monitoring campaign of two Danish mature stormwater ponds which were used to calibrate and validate the model. One general calibration covering 6 consecutive months together with two additional short-term calibrations during summer (31 days) and winter (56 days) were carried out applying the data series from one of the ponds. The calibrations showed a good agreement between measured and modeled data for the time spans evaluated. The calibration showed that growth rates for the three groups of primary producers were approximately the same for the two calibrations. The validation for both trends of DO and pH were well simulated, even though pond Aarhus showed a better agreement of the absolute values. The eutrophication model could be successfully calibrated to two stormwater ponds and has the potential of providing a tool for improving the design of stormwater ponds by taking into account the behavior of the plant ecosystem.