Abstract: Through two year's observation, it was found out that no trees ever withered or died in the young Eucapytus manldnlensis×Tophroria candida plantation when the mean precipitation was 17% less than that of the normal years. Even if in the driest season from March to May,soil water content could meet the need of the young trees, In terms of water input loss, the loss of crown-intercepting water amounts to 10% of the total precipitation,while surface run-off only 3%. In the dry and hot river valley areas where there is no subterranean water available and rainfall is the only water source,afforestation and plant vegetation recovery should aim at obtaining the most water input.