中文摘要：

以天山北坡的鸟鲁木齐河、玛纳斯河和奎屯河作为典型流域，以出山口水文站多年序列水文气象实测资料作为分析样本，基于定性和定量相结合的研究方法，利用多种水文统计模型．全面分析典型流域近50年的流域水文综合特征、判断径流年内／年际变化特征及变化趋势．为深入了解天山北坡内陆河径流的多年变化过程和规律提供科学参考。研究结果表明，天山北坡典型流域在近50年水文特征及其变化趋势上具有较大的相似性：径流年内分配不均匀，集中度高；年际变化较稳定、Cv值逐步增大、多年平均径流量的距平变化幅度偏大，特别是1990年后各流域Cv值增大与径流变化增大趋势较明显。

英文摘要：

This paper analyzed the hydrological characteristics and change trend in the basins of Urumqi, Manas and Kuitun of the north Tianshan during the last 50 years. Long time series data from the hydrometry stations of the river outlets were used for analysis with certain hydrologic statistical models. The results indicate that the runoff of the rivers have strong similarity in their hydrological characteristics. The distribution of the annual runoff is highly imbalaneed between the four seasons, and concentrates in summer. The concentration degree of the runoff is comparatively high in all the three rivers. The value of Cv is relatively small during the whole study period, but increasing gradually. Significant increase occurred in Cv value after the 1990s. The runoff changes also show an overall increasing trend, and it is very obvious after 1990s.