Hydrologic connectivity between geographically isolated wetlands and surface water systems: A review of select modeling methods
Geographically isolated wetlands (GIW), depressional landscape features entirely surrounded by upland areas, provide a wide range of ecological functions and ecosystem services for human well-being. Current and future ecosystem management and decision-making rely on a solid scientific understanding of how hydrologic processes affect these important GIW services and functions, and in turn on how GIWs affect downstream surface water systems. Consequently, quantifying the hydrologic connectivity of GIWs to other surface water systems (including streams, rivers, lakes, and other navigable waters) and the processes governing hydrologic connectivity of GIWs at a variety of watershed scales has become an important topic for the scientific and decision-making communities. We review examples of potential mechanistic modeling tools that could be applied to further advance scientific understanding concerning: (1) The extent to which hydrologic connections between GIWs and other surface waters exist, and (2) How these connections affect downstream hydrology at the scale of watersheds. Different modeling approaches involve a variety of domain and process conceptualizations, and numerical approximations for GIW-related questions. We describe select models that require only limited modifications to model the interaction of GIWs and other surface waters. We suggest that coupled surface–subsurface approaches exhibit the most promise for characterizing GIW connectivity under a variety of flow conditions, though we note their complexity and the high level of modeling expertise required to produce reasonable results. We also highlight empirical techniques that will inform mechanistic models that estimate hydrologic connectivity of GIWs for research, policy, and management purposes. Developments in the related disciplines of remote sensing, hillslope and wetland hydrology, empirical modeling, and tracer studies will assist in advancing current mechanistic modeling approaches to most accurately elucidate connectivity of GIWs to other surface waters and the effects of GIWs on downstream systems at the watershed scale.