The researchers analyzed the yearly highest and lowest water levels in the Yangtze River to find patterns. They used special methods to study the data from 1964 to 1987. The results showed that the highest water levels had periods of 3.14, 7.33, 2.2, and 5.5 years in different locations. The lowest water levels had periods of 2.44 to 3.14 years, and 2.2, 5.5, and 11 years in different places. These periods show how the river's water levels change over time, and also reflect the influence of ocean tides. This research helps us understand how the lower part of the Yangtze River evolves.