Water stages play a critical role on flood control, water supply, navigation, and ecology in rivers. Investigation of water stages provides better understanding of riverbed evolution processes and river management. Based on the hydrological observation in past 70 years, the changes of low-flow and flood stages were investigated by a combination of Mann-Kendall test, moving t-test, and wavelet analysis. 1) In accordance with the location, the middle Yangtze River was divided into upper reach, middle reach, and lower reach. Water stages in the upper reach show a decreasing trend, while that in the middle reach present an increasing trend, and the lower reach are mainly dominated by natural evolution. 2) The mutation year of water stages in the upper reach was around 1985, indicating that the Gezhouba Dam facilitated the reduction of water stages. The trend mutation in the middle reach was in 1969, which was consistent with the implementation of Jingjiang Cutoff. 3) Human activities aggravated the change of water stages, leading the primary period of water stage time series to exceed 20 years. 4) In the upper reach, the reductions of water stages were attributed to the riverbed erosion induced by human activities. While in the middle reach, the recent falling effects of riverbed erosion can hardly offset the rising effects of the channel resistance on water stages. 5) In the future, the increasing trend in the middle reach may be arrested due to the riverbed erosion induced by the Three Gorges Dam. Long-term observation of the flood stage must be conducted in the middle Yangtze River.

水位在河流的防洪，供水，航行和生态中起着至关重要的作用。对水位的调查可以更好地了解河床的演变过程和河流管理。基于对过去70年的水文观测，低流量和洪水期的改变是由曼-肯德尔测试的结合研究，移动ŧ测试和小波分析。1）根据地理位置，将长江中游分为上游，中游和下游。上游水位呈下降趋势，中游水位呈上升趋势，下游水位主要受自然演化控制。2）上游水位突变年在1985年左右，表明葛洲坝大坝促进了水位的减少。中游的趋势突变发生在1969年，与靖江断流的实施相吻合。3）人类活动加剧了水位的变化，导致水位时间序列的主要时期超过20年。4）在上游，水位的减少归因于人类活动引起的河床侵蚀。在中游地区，最近河床侵蚀的下降作用几乎不能抵消河道阻力对水位的上升作用。5）将来，由于三峡大坝引起的河床侵蚀，中游的增长趋势可能会被遏制。必须在长江中游进行长期的洪水观测。