Answer:
It is extremely important economically.
Explanation:
The Hai River and its tributaries form one of the most important river basins in China. Because it flows through a heavily populated area and also one used intensively for agricultural purposes, the river is essential for irrigation and also for human water supply.
The river and its tributaries connect the Chinese capital of Beijing to another one of the nation's largest urban agglomerations, Tianjin.
The main reason, which I have read about in some books, is that they do not permit industrial building on those islands, so who would want to live there? It is a very bare bones society.