Cooperative Fish and Wildlife Research Units Program: North Carolina
Education, Research and Technical Assistance for Managing Our Natural Resources

Hydrologic connectivity, the intricate network of water pathways linking diverse aquatic habitats, plays a pivotal role in facilitating the exchange of aquatic species and materials between the main river channels and adjacent waterbodies. This study quantified hydrologic connectivity for 1,283 floodplain lakes within the historical floodplain of the Lower Mississippi River using metrics derived from satellite imagery, stream gauge, and geospatial information. Our goal was to assess patterns of connection frequency between lakes and streams in this floodplain. We estimated eight metrics descriptive of the temporal aspects of hydrologic connectivity and identified trends in the connectivity characteristics of lakes by lake features and by the sizes of adjacent linked streams. We found that each lake maintained a signature recurring pattern of connection, with specific months of connectivity followed by periods of disconnection, which is likely tied to the interaction between lake characteristics and precipitation seasonality. Larger lakes typically exhibited increased hydrologic connectivity compared to their smaller counterparts. This effect is likely due to the larger surface area and volumetric capacity that large lakes inherently have, which facilitates interaction with adjacent waterbodies. Conversely, smaller lakes may experience limited or no hydrologic connectivity, particularly if they are geographically isolated. Additionally, because of smaller volumes, smaller lakes are more vulnerable to losing storage during dry periods, which can result in temporary or long-term isolation from neighboring rivers. Regardless of size, lakes connected to large streams exhibited more prolonged, recurring, and seasonally indistinct connections, as well as a higher degree of continuity in their hydrologic interactions. There was often reduced connectivity in lakes surrounded by increased agriculture. However, these generalizations are subject to many exceptions since local factors and human-induced changes such as levees, artificial channel, and weirs may override the general trends. The insight gained from this hydrologic connectivity analysis offers the possibility to augment floodplain management actions, for example, by allowing the building of strategic frameworks for restoring connectivity and ecologic integrity, or to inform the control of invasive species spread that typically plagues agricultural floodplains.