中文摘要：

河流水文过程的变化与生态环境系统变化之间存在着极强的响应关系,研究河流水文要素的变化趋势对认识河流生态系统演变的规律及机理有重要意义.通过对黄河中游潼关断面径流要素、洪水要素、河流泥沙要素的统计特征进行分析,揭示不同水文指标在长期演变过程中的发展规律及突变特点,分析由此引发的生态系统响应过程,并进一步挖掘影响河流生态水文系统演变的关键因素.结果表明,黄河中游生态水文系统中改变强烈的水文要素主要有大洪水发生次数、径流年际丰枯变化、年内分配以及水文极值发生时间等.受气候变化和人类活动（水库运行及引水）的影响,中游水文系统要素发生了较大变异,将对河道内、洪泛区和湿地的生物数量、多样性以及其繁衍、迁徙、洄游行为产生影响,且这种影响与水库的累积作用和不科学的取用水制度密切相关.

英文摘要：

This paper is entitled to study the influence of the climatic change and human activities on the hydrologic constituent elements in the middle reach of Yellow River based on the analysis of the current research findings. In order to understand the long-rim evolutionary regularities, mutation characteristics of the river eeo-hydrologic system, it is crucial to determine the hydrological indicators involving such factors as the runoff element, flood element, the river sediment rate. It is just for this reason that the present paper is focused on the analysis of the above said elements and their changing regularities under the influence of the climatic change and that of human activities roughly divided into seven aspects, including the changes in annual runoff, intra-annual distribution of the runoff, annual extreme water condition, time-change regularities of the annual extreme water canditions, high and low pulse, small floods and large floods, semimetal discharge of silt-mud, and so on. To do a good job in our research, we have introduced some statistical methods into our work, for example, Mann-Kendall, which are helpful to measure the impact from the point of view of climatic change and human activities. In addition, we have also analyzed the likely eco-responses to the river＇s ecologi- cal system resulted from the changed hydrologic elements so as to tap off the critical factors influencing the river eco-hydrologic system evo- lution. The research results show that considerable changes have tak- en place in the middle-reach of the River in the past 50 years. Great changes have taken place in the hydrological indexes due to the cli- matic change and human activities, which include the numbers of large floods, annual runoff, intra-annual distribution, minimum and maximum water current coming time and so on. Such changes have also influenced the reproduction, migration and migratory behaviors of some living creatures in the river channel, flooded area and wet- lands. Further-going analysis has allowed us to f