The role of a seasonal lake groups in the complex Poyang Lake-floodplain system (China): Insights into hydrological behaviors

Seasonal lakes that exist in floodplain settings have significant effects on hydrological and ecological processes and are highly susceptible to various changes; however, they are rarely investigated, mainly because of the large extent and remoteness of floodplains. This study uses physically based hydrodynamic modeling in combination with a bathymetry adjustment approach to investigate the coupling effects of 77 seasonal lakes (defined as the seasonal lake group) on hydrological behaviors within the Poyang Lake-floodplain system (China) from a systemic perspective. Elucidation of the role of seasonal lake groups could benefit from hydrodynamic modeling, which enables complex lake-floodplain simulations and comparison analyses of natural (original bathymetry) and hypothetical conditions (adjusted bathymetry). In the present study, the simulation results showed that the temporal influences of the seasonal lake group on water levels, lake outflows, and inundation dynamics were greater during dry seasons than wet seasons for both the dry (2006) and wet years (2010). The spatial effects of the seasonal lake group on the hydrology of the lake's floodplains were stronger than those of the main lake for both hydrological years. The findings demonstrate that the seasonal lakes are likely to have very limited effects on the main lake and the associated flood levels. On average, the role of the seasonal lake group during the dry seasons was around several times stronger than that during flood seasons in terms of the magnitudes of hydrological responses. Additionally, it is expected that the seasonal lake group may exert an important role in influencing the surface hydrological connectivity and associated dry-wet hydrological shift across lake-floodplains, indicating a dominant role of the floodplain bathymetry changes. Overall, the results of this study will support management and planning of Poyang Lake and other similar floodplain regions with numerous small, shallow, and seasonal lakes by providing more reliable information regarding bathymetry changes, water management and lake-floodplain interactions to decision-makers for improved floodplain protection strategy.