Surface water connectivity of seasonal isolated lakes in a dynamic lake-floodplain system

Abstract

The dynamic of surface water connectivity along floodplains can be complex, and is of great significance to such ecological functions as flood protection, sediment transportation, nutrient retention, and the provision of wildlife habitats. However, connectivity quantification is currently incipient due to the scarcity of high spatial-temporal resolution observations and suitable connectivity metrics. This study generated a 30-m and 8-day surface water series of the Poyang Lake National Natural Reserve (PLNNR) in China by fusing Landsat and MODIS imagery. A geostatistical analysis was applied to quantify the surface water connectivity based on wet/dry binary state data derived from the fused images. The results demonstrate that the geostatistical method based on remote sensing is reliable and objective for quantifying the surface water connectivity in a complex lake-floodplain system. The highest connectivity function occurred around the flood peak, and lasted longest in the typical flood year. The seasonal isolated lakes, rivers, and main lake were interconnected via channelized and overbank flow paths at different stage thresholds. Under the combined effect of flood pulse and surface water connectivity, a seasonal isolated lake expanded more quickly after connection than before during the rising period, and shrank more slowly after isolation than before during the receding period. This study provides a novel insight into quantifying surface water connectivity, which helps policymakers understand floodplain behavior, both for this particular event and in general.