A structurally dynamic model developed [Ecol. Model. (in press)] for Lake Mogan was applied to set up prognosis for the response of the lake to the increased phosphorus input. It was found that a shift to a turbid water state takes place at phosphorus concentration between 0.16 and 0.25 mg TP l(-1) resulting in a significant decrease in the submerged plants. Consequently, above the threshold P level, the submerged plants abruptly disappeared, while phytoplankton became dominant. The model simulated the recovery of the lake through reducing the increased phosphorus concentration in the inflow to the original level. Submerged plants redeveloped at a low phosphorus concentration about (0.1 mg TP l(-1)). However, the recovery took very long time because the lake first performed long resilience probably owing to the accumulation of phosphorus in the sediment. The shifts between the clearwater and turbid water states followed a hysteresis for the structurally dynamic model based on the maximum exergy storage hypothesis [Ecol. Model. 7 (1979) 169]. The results presented are completely in accordance with how shallow lakes respond to the changing phosphorus levels with a hysteresis in the range 0.10-0.25 mg TP l(-1) [Ecology of Shallow Lakes, Chapman & Hall, London, 1997; Nature 413 (2001) 591]. Therefore, the model result may be considered a support for the maximum exergy storage hypothesis. (C) 2003 Elsevier Science B.V. All rights reserved.