In historical period fTaihu Lake expanded constantly at a rate of 0.37km/a.According to the analysis and calculation of sediment transportation balance t there are about 9.28×10⁵t of sediments which are transported into Taihu Lake annually from the collapse of lake bank and the different sediment transportations between upstreams and downstreams of Taihu Lake river system.Even though the amount of sediments accumulated in Taihu Lake annually was relatively small,yet,in a long term,it had profound impacts on the evolution of Taihu Lake.At present,the evolution trend of Taihu Lake in nature is that it expands at a rate of 0.168km²/a in area and reduces at a rate of 3.95×10⁵m³/a in volume.Taihu Lake is getting more and more shallow and flat.However,Taihu Lake has been reducing at a rate of 4.58km²/a in area since 1949 because of reclamation of land from the lake.