Water depth affects the growth of underwater plants like Vallisneria natans and Myriophyllum spicatum in lakes. Researchers studied how different water depths (0.5m, 1.5m, 2.5m) impact these plants when grown together. They found that both plants grow best at a moderate depth of 1.5m, with the highest biomass and growth rates. Vallisneria natans does better in deeper water, while Myriophyllum spicatum prefers shallower water. In deep water, both plants grow taller above the water but have shorter roots below. As water gets shallower, Vallisneria natans becomes more competitive. This study suggests that changing water levels in lakes can affect the abundance and structure of underwater plants. When restoring lakes, it's important to consider the sunlight needs of key plants like Vallisneria natans when adjusting water levels.