A 2-D numerical model was used to study the response of fresh water transports and distributions on the abrupt changes of topography in the Pearl River Networks (RNPRD). The results indicate that both the tidal forces in Jiaomen and Humen and the runoff power in Modaomen are intensified, which leads to a fresh water movement from the northeast to the southwest side of the West and North River Delta Networks. However, the water distributions in the East River Delta Networks remain almost the same. The residual currents in the RNPRD decreased dramatically in the West and North River Delta Networks due to the increasing volume of the river channels. This decreasing trend was intensified in the North River Main Channel due to the annual water discharge redistribution in the RNPRD.