Monitoring surface-water connectivity in a coastal lowland river using field-based data loggers

Abstract

The concept of hydrologic connectivity has commonly been used as an indicator of river habitat health and considered in environmental flow policies and river management schemes. Field-based data loggers, used to infer flow intermittency, have been used to study the connectivity in ephemeral channels in a variety of physiographic environments; however, no previous studies have utilized and analyzed them in portions of perennial channels and floodplains that experience inundation intermittently. To address this gap, we developed an array of Stream Temperature, Intermittency, and Conductivity Loggers (STICL) and deployed them in a coastal lowland river to analyze temporal changes to hydrologic connectivity induced by surface water in the longitudinal, lateral, and vertical dimensions of the channel and the floodplain. We examine the efficacy of STICLs to monitor surface-water connectivity within the floodplain that experience intermittent inundation. We also examine influence of hydrologic regime and geomorphology on the variations in connectivity. Our results show that the electrical conductivity (EC) records from our STICLs can capture flood inundation dynamics and how these dynamics affect surface-water connectivity. Our estimates of flood inundation duration and the dynamics of surface water connectivity can be improved by better accounting for how EC can vary with temperature and by handling the uncertainty in our STICLs readings in a more explicit manner. The STICLs provide a promising tool to study river hydromorphological processes in detail. Thus, we recommend the development of formal approaches and frameworks for deploying and analyzing these types of data loggers within lowland landscapes.