Abstract: In 2002, China launched the South-to-North Water Transfer Project after completing a 50-year feasibility study. By 2050, the three-route (i.e., East, Middle, and West) project will be capable of transferring 44.8 billion m3/year of water from the water rich Yangtze River to the arid north to alleviate water shortage and help secure a balanced social and economic development across the nation. However, diversion of such a large quantity of water could profoundly change the riverine environment of the upper Yellow River and the lower reach of the Han River, a tributary of the Yangtze River and the water supplying area of the project’s Middle Route, because of changes in the annual discharge. Secondary salinization seems inevitable in the water receiving areas of the North China Plain, and decrease in the discharge of the Yangtze River will result in seawater intrusion into the Yangtze Delta. This paper describes the project and discusses its environmental implications. Additionally, a long-term monitoring strategy under the umbrella of the Chinese Ecological Research Network is proposed for environmental monitoring.