Why didn't the South-to-North Water Transfer Project be built into a canal?

There are many reasons for not using the canal. Personally, I think these reasons have shortcomings. Please forgive me and discuss them with you. (I can use more popular language)

1. The South-to-North Water Transfer Project passes through many provinces and cities. It is not Ma Pingchuan's project to bring water here, so it is quite difficult to dig the canal;

2. Now that land is in short supply, canals will occupy a lot of land, and will also produce a large number of immigrants. The resettlement work is extraordinary. The resettlement in the Three Gorges reservoir area is a huge project, and you can learn more about it yourself.

3. Canal will cause pollution and waste of water resources. After all, the South-to-North Water Transfer Project is not based on shipping, but on water transfer, so first of all, high-quality and high-quantity water transfer should be the premise;

4. If the canal is put into use, the maintenance workload will be great, and it should be monitored every year in flood season. In case of a flood (inevitable), it will not be worth the loss. Again, the main purpose is to divert water;

5. In the present form of water diversion project, the amount of water diversion can be better controlled and the loss of water resources can be avoided to a greater extent;

I'm just a senior majoring in water conservancy and I'm not good at it. I can only think of so much for the time being. But we can continue the discussion later, hehe.