The Grand Korean Waterway is a proposed 540-kilometer (336 mile) long canal connecting Seoul and Busan, two of South Korea's largest cities. The canal would run diagonally across the country connecting the Han River, which flows though Seoul into the Yellow Sea, to the Nakdong River, which flows through Busan into the Korea Strait. The proposed canal would be 540 kilometers in length and traverse difficult mountainous terrain. However, the length of the construction would only be 40 km linking the Han River with the Nakdong River.

this project of making 1 big river from 4 rivers existing now would be a real ecological disaster if it comes to realisation.
it will destroy ecosystems and it will be impossible to step backward afterthat.
this project is the one of the new korean president, and it is clear that the main reason is not the use of the grand canal but the economic boom while it is constructing.