Water level fluctuations control wetland hydrological connectivity in driving the integrity of wetlands

Abstract

Wetland hydrological connectivity, which is altered by water level fluctuations, can dramatically result in a series of changes in wetland structure and function. However, the responses of wetland habitats to changes in hydrological connectivity and its mechanisms remain unclear. This study provides a new concept of effective hydrological connectivity that considers wetland water level fluctuations. Wetland InSAR technology was used to investigate the structural connectivity of 14 wetland patches in combination with hydrological barriers and relative water levels in the Momoge National Nature Reserve, China. The 14 wetland patches were categorized into three types as follows: wetland patches with near-natural hydrological processes, wetland patches with hydrological processes under anthropogenic regulation and wetland patches with hydrological processes regulated by river flooding. Water level fluctuations further validated the consistent changes in hydrological regimes within three types of wetland patches to varying extent. Specifically, the coefficients of variation (CVs) of the water levels were 0.75 ≤ CV ≤ 0.90, CV < 0.75, and CV > 0.90 for the three types of wetland patches (from I to III), which induced differences in effective hydrological connectivity. Subsequently deviations in effective hydrological connectivity induced different ecological responses, i.e., the ecological resilience is accordingly −1.38, −0.78, and −0.76. The differences in water level thresholds for the intensity of hydrological connectivity provide further evidence of differences in the mechanisms of hydrological action that maintain different wetland habitats. Taken together, these results indicate that the formation and maintenance of wetland habitats depends on the existence of distinct hydrological conditions.