The study looked at how different tidal patterns affect water levels in rivers that flow into the sea. They found that river flow and interactions between tides and rivers are the main factors influencing water levels. The contribution of tidal patterns like diurnal and quarter-diurnal tides is minor compared to river flow. The method used in the study helps understand how rivers and tides impact water levels in estuaries, which can be useful for managing water in tidal rivers like the Yangtze.