Water depth affects the growth of underwater plants in lakes. Vallisneria natans and Hydrilla verticillata are common in the Yangtze River. Deeper water suppresses their growth, with Vallisneria natans doing better than Hydrilla verticillata in deep water. Hydrilla verticillata grows taller in deeper water but with fewer plants. Vallisneria natans also adapts to deeper water but not as well. Lowering water levels can increase total plant biomass but may reduce the dominance of Vallisneria natans.