Abstract: Urbanization is a doubleedged sword for water use change. It can stimulate economic development and increase total water use, and can also optimize water use structure, enhance water use efficiency and decrease total water use. To measure the exact driving effects of urbanization to water use change, a complete decomposition model was established, and was applied in Zhangye City, which is a typical oasis city in the Heihe River Basin. Results show that, both the urbanization processes of population and economy have decresing effects to total water use, and increasing effects to water use efficiency. From 2000 to 2011, total water use was decreased 4.67×10⁸ m³ by population urbanization effects and 12.64×10⁸ m³ by economic urbanization effects. Per capita water use was decreased 373 m³ per person by population urbanization effects. Ten thousand Yuan GDP water use was decreased 1 210 m³ ten thousand Yuan by economic urbanization effects. Moreover, the faster the urbanization processes of population and economy are, the greater the total water use will decrese and the water use efficiency will increase. Therefore, restricted by scarce water resources, oasis cities in arid areas of northwest China should accelerate the urbanization process, and take urbanization as an important task or approach to optimize the population structure, economic structure and water use structure, and enhance the economic efficiency and water use efficiency, so as to obtain a benign circle among the water-ecology-economy system. The results of this paper have significance to understand the relationship between urbanization and water resources utilization in arid areas of northwest China.

Key words: urbanization, water resources utilization, driving effects, complete decomposition model, arid areas of northwest China