The prosperity of the Daxia was short,however,in that ruling,long for population,and then unbridled plunder,which result in population had sudden growth in Time of Helian bobo where the City of Tong wan as it′s center,and reached the population peak Tongwan′s population also attained culminating point to this day.

The rise and fall of Tongwan city with the environmental change of Mu Us Sandy Land;

The building function of Tongwan city Xicheng south horse face;

The problem of environmental changes of Erdoss Plateau has been antroversial in the academic circle, among which the focus on this problem lies in the truly geographic position of Qiwu mountain to the north of Tongwan city (capital of Hsia kingdom )during the period of sixteen states.

Historical natural landscape of Tongwancheng area in northern Shaanxi Province and migration rate of Mau Us Desert;