The ring growth of the branches of Populus euphratica Oliv. reflected the changes in water flow of the Tarim River. We can thus find information about the emergent water transportation to the Tarim River through the investigation of the increment of the branch of P. euphratica. After the emergent water transportation the growth of P. euphratica branches in diameter increased significantly, mostly since the year 2001, in some cases up to 3.85 times the growth before the water transportation project was carried out. The ratio of the branch diameter after and before water transportation was negatively correlated to the distance between the tree and the river. The pattern of the change in branch diameter increment indicates that the extent of the influence of the emergent water transportation reached 900 m from the river in 2003.