**4. Environmental change and sustainable development of river basin**

As an important typical spatial unit, basin has the characteristics of coordinating the upstream and downstream subsystems and coordinating the resource elements of each unit. There is a close relationship between the fluctuations of water resources in the basin. Under the condition that the total amount of water resources is fixed, it is of great significance to play the role of overall planning and unified allocation for the basin as a whole and each economic unit.
