Impact of Three Gorges Reservoir water supply regulation on habitat suitability of typical submerged plants in East Dongting Lake

Submerged plants are important species for ecological restoration of water in East Dongting Lake, and water depth is one of the key hydrodynamic factors affecting the growth of submerged plants. In order to quantitatively describe the impact of different water supply modes of the Three Gorges Reservoir (TGR) on typical submerged plants growth habitat in East Dongting Lake, taking Vallisneria spinulosa as the target species, the relationship between different outflow from TGR and the weighted usable area (WUA) of Vallisneria spinulosa growth habitat in East Dongting Lake during TGR water supply operation was established by using physical habitat simulation model (PHABSIM). The results showed that the suitable water depth range for the growth habitat of Vallisneria spinulosa was 0.2~1.8 m, the optimal water depth range was 0.5~1.0 m. After TGR implementing the water supply operation, WUA of Vallisneria spinulosa growth habitat in East Dongting Lake showed a uniform upward trend totally. During the period of TGR water supply, the outflow was 5 500~10 500 m³/s. With the increase of the outflow of TGR, WUA corresponding to the optimal water depth range for Vallisneria spinulosa growth habitat firstly increased and then decreased. When the outflow range was 9 500 m³/s, the maximum WUA was 74.46 km². It could be considered that the optimal outflow range of Vallisneria spinulosa was 8 500~10 500 m³/s. The results were expected to provide reference for restoring and protecting the water ecological environment in East Dongting Lake through TGR ecological scheduling.