The Yangtze River is the most longest river in Asia and the third longest in the world behind the Nile and the Amazon. Originating from the Tibetan Plateau at an elevation higher than 5000 m, the Yangtze River flows eastwards into the East China Sea (ECS). The Yangtze River freshwater contributes about 80% of the total discharge of fresh water from rivers around the Yellow Sea and ECS. Construction of the Three Gorges Dam (TGD), scheduled in the completion of 2009, is under way on the world's largest hydroelectric dam at the Three Gorges in the middle of the Yangtze River. Many environmental and sociological problems are included, though the TGD will produce positive effects socio-economically. By reducing the Yangtze discharge after the completion of the TGD, the changes in the physical, chemical, biological, and geological condition in the East China Sea Basin is expected. Besides, the south-to-north water transfer project to divert water from the Yangtze River to the country's thirsty northern areas was started in 2002. The water diversion the Yangtze River to the north will result more in the reduction of freshwater outflow to the ECS. The study to examine the effects of diminished the Yangtze River outflow on the oceanographic environmental in the ECS is needed immediately.