The causes of climate dry in loess plateau area of Gansu province are autumn rain precipitations, great variation in year-to-year precipitation, less effective precipitation, air drying and windy, therefore,freguent natural disaster can lead forest ecological construction more and more difficult.

After statistically analyzing the relationship of the 10 days total precipitation as the landslide occurring on 1 615 samples of Chongqing, it can be obtained the relationship of the rainfall, the time of the landslide taking place and the probability of the landslide taking place,which is given landslides induced by the effective precipitation definitions, calculati.

through the analysis on relationship and change trend between the precipitation and effective precipitation in growth period of winter wheat,effective precipitation calculation models under different time scale were given in Xinxiang area,which to meet the demand of regional agricultural development and water resources optimization management.

Based on the pertinent iterature,the calculation methods of effective rainfall in growing period on dry crop was analysed and summarized in this paper,which combines with research situation of calculation methods of effective rainfall.

Based on the small-scale hydrology theory and the effective rainfall,a new soil water resources calculating model was put forward,which calculated the soil water resources by water balance principle.