The regional water balance model is applied to calculate the soil water resources within the whole river basin including the upper,middle and lower reaches of the Yellow River and the region of the basin in the Northwest China.

In northern region of China,rainfall amount is small and the water resources is scarcity,soil water resources plays a key role for the planting and growth of crops,especially in the region without irrigation condition.

Evaluation of regional soil water resources and its research development;

Study on the model of the plain soil water resources quantity;

Calculating model of soil water resources in plain area;

The paper defines soil water resource, stresses the significance of soil water resource research, analyzes components of soil water resource, and proposes methodology for evaluating soil water resource.

The concept of soil water resource is proposed and defined in this paper.

Based on the analysis of soil water balance considering crop transpiration,the concept of soil water resource and its characteristics such as dependence on precipitation,easy consumption,unable exploitation,usability on site and possibility to be controlled are discussed.