Environmental flow assessment in a lake‐marsh system with reverse seasonal hydrological patterns.

Environmental flow (e‐flow) assessment is essential for the ecological protection and restoration of lake‐marsh systems. Previous studies on e‐flow assessment for lake‐marsh systems focused on lake‐marsh systems with natural seasonal hydrological patterns (i.e., low water level in winter and high water level in summer). However, they have not considered lake‐marsh systems with reverse seasonal hydrological patterns (i.e., high water level in winter and low water level in summer). The reverse seasonal hydrological patterns impose seriously negative impacts on waterbirds, because the hydrological patterns could lead to limited plant germination in spring and massive plant death in summer, leaving few plants available as food for waterbirds in winter, and could consequently reduce the sheltering and forageable areas for waterbirds. This study took Hongze Lake Wetland National Nature Reserve in China as the study area. Based on the habitat requirements of waterbirds, the sheltering and forageable areas for waterbirds under different water‐depth and aquatic plant distribution scenarios were calculated. By exploring the impacts of reverse seasonal hydrological processes on waterbird habitats, we determined the necessary e‐flows for lake‐marsh systems with reverse seasonal hydrological patterns to meet the needs of waterbird habitat. The results showed that the water level of Hongze Lake should be controlled to 13.0–13.1 m in March, 12.5–12.6 m in July, and 12.9–13.0 m in October, which can meet the needs of waterbirds for both shelter and foraging. [ABSTRACT FROM AUTHOR]