The Pearl River Delta (PRD) is a complex river network system

its hydrodynamic process is controlled both by runoff and tide

different from other estuaries in the world. During the last 50 years

the PRD area had undergone some largescale human activities (such as floodgate building

sand excavation

channel regulation)

which changed the morphology of the river bed

and resulted in the hydrodynamic characteristics different from the 1950s. 1D river network hydrodynamic model was developed to simulate the river flow of 1950s and 1990s.The results show that the water level in flood seasons of the PRD was significantly lower than that in 1950s

and the surface grads of two main rivers (Xijiang and Beijiang) were dropped from 7.2 cm/km and 7.1 cm/km to 4.1 cm/km and 4.9 cm/km

respectively. In dry seasons

the change was not so significant. A numerical experiment was conducted to figure out the impact of channel evolution on the hydrodynamic process.In the experiment

the water surface level of the Xijiang river and Beijiang were dropped from 7.1 cm/km and 7.2 cm/km to 4.2 cm/km and4.7 cm/km

respectively

under the same conditions

which indicates that the main reason for low of water level in the PRD was the change of river bed. The experiment also figures out that the dividedflow ratio was readjusted heavily where the river bed changed dramatically.