Assessment of water storage response to surface hydrological connectivity in a large floodplain system (Poyang Lake, China) using hydrodynamic and geostatistical analysis

Abstract

Floodplains play a significant role in affecting the transport of water, dissolved matter and sediments during wide-ranging drying and wetting. This study uses a hydrodynamic model and geostatistical method to explore the variations of water storage and its relationship with the surface hydrological connectivity, exemplified by the large Poyang Lake-floodplain system (in China). The simulations show that the floodplain storage exhibits largely similar behavior to that of the total lake water storage, but the water storage in the main lake is distinctly higher than the floodplains. The lake storage is estimated to be from 20 × 108 to 163 × 108 m3 and differs considerably between seasons, and the contribution of the floodplain to the total lake storage varies from 18 to 34%. Geostatistical analysis reveals that the degree of surface hydrological connectivity can be classified as high connectivity in summer, low connectivity in winter, and intermediate connectivity during other seasons. Higher variability of water storage and lower frequency of hydrological connectivity are found in the seasonal floodplains, whereas the lower variability and higher frequency are observed in the main lake, indicating that water storage is inextricably linked to the dynamic behaviors of surface hydrological connectivity. Additionally, the estimated water storage significantly increases from the low and intermediate conditions to the high connectivity condition, mainly due to the key process of the west–east connectivity in controlling lake-floodplain interactions. This study improves understanding of Poyang Lake floodplain behavior and other similar floodplain systems by providing knowledge of water balance, water allocation and water management.