Abstract: Estimating the maximum stable navigation depth of waterway is a prerequisite for optimizing the utilization of water depth resource. Enhancing the process of calculation holds significant importance in evaluating waterway depth potential. To ascertain the maximum stable waterway depth of Chenglingji-Wuhan section of the middle reach of Yangtze River, we refined the processes of calculating river phase relationship parameter, waterway depth correction coefficient, and split ratio in the estimation method. In consideration of both branching and non-branching river sections, we determined the maximum stable waterway depth of Chenglingji-Wuhan section under various flow rates and river widths. Key findings include: 1) The process of calculating stable waterway depth can be simplified and improved by establishing the empirical relations of flow rate Q against river phase coefficient α, shape coefficient k, river phase index β, and river width B. 2) At a design navigation guarantee rate of 98%, the stable waterway depths of Chenglingji-Wuhan section based on natural endowments are 5.98, 5.64, and 5.30 meters for navigation widths of 150, 200, and 250 meters, respectively. At a flow rate of 20 000 m³/s, the stable waterway depths with the same navigation widths are 12.56, 11.89, and 11.22 meters, while for a flow rate of 30 000 m³/s, these values are 16.81, 16.16, and 15.49 meters.

Key words: stable navigation depth, improved calculations, river phase relationship, water depth correction coefficient, branching river section, middle reach of Yangtze River