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Geographically Isolated Wetlands are Part of the Hydrological Landscape
Citation:
Rains, M., S. Leibowitz, M. Cohen, I. Creed, H. Golden, J. Jawitz, P. Kalla, C. Lane, M. Lang, AND D. McLaughlin. Geographically Isolated Wetlands are Part of the Hydrological Landscape. Hydrological Processes. John Wiley & Sons, Ltd., Indianapolis, IN, 30(1):153-160, (2016).
Impact/Purpose:
A recent EPA technical report supporting the new Waters of the US rule reviewed more than 1,200 peer-reviewed papers and concluded that additional research focused on the frequency, magnitude, timing, duration, and rate of change of fluxes from non-floodplain wetlands – including geographically isolated wetlands (GIWs) – to downgradient waters is needed. This manuscript begins to fill in these research gaps on GIWs. That extensive and dynamic hydrological flowpaths connect landscapes in four dimensions is well known in regards to stream networks. More poorly acknowledged and understood is the role that GIW nodes and related flowpath edges play in the functioning of the broader hydrological network, including the stream network. This represents a critical knowledge gap, especially in archetypal GIW-dominated landscapes (e.g., vernal pools, prairie potholes, Carolina bays, etc.) where the number of these GIW nodes and related flowpath edges is large. Here we provide a new conceptual framework that can be used to generate hypotheses regarding how these systems vary over space and time, with a specific focus on the effects of GIWs on flows in downgradient waters. Specifically, we conceptualize GIWs as nodes in hydrologic networks that can receive, store, and send water, and consider the network scale effects of GIWs on flow generation. The cumulative effect of many GIWs can play an important role in landscape-scale hydrology by regulating the frequency, magnitude, timing, duration, and rate of flows to downgradient waters. This cumulative effect emerges from lag, sink, and source functions resulting in time-varying flows being directed towards downgradient waters along overland, shallow subsurface, and deep groundwater flowpaths. GIWs perform lag, sink, and source functions that can influence the chemical, physical, and/or biological integrity of downgradient waters, especially when considered in aggregate. A concerted research effort that examines these functions could transform our understanding of watershed-scale hydrology, facilitating a better understanding not only of the role played by wetlands but the specific roles played by GIWs and how these roles change depending upon inherent spatial heterogeneity and temporal variability. This could focus on showing that GIWs express a full portfolio of services along a continuum from connection to isolation, and helping in the determination of the extent to which this portfolio of services plays a role in maintaining the physical, chemical, and biological integrity of downgradient waters. This manuscript is an extra product of SSWR 1.1B that emerged from a November 2013 “Isolated Wetlands Research Workshop” that was held at the Joseph W. Jones Ecological Research Center.
Description:
A recent report by the U.S. Environmental Protection Agency concluded that all wetlands located on floodplains and/or within riparian areas have significant chemical, physical, and/or biological connections with downgradient WOUS. The report concludes that other wetlands – including the vast majority of geographically isolated wetlands (GIWs, or wetlands completely surrounded by uplands), which are not located on floodplains and/or riparian areas – occur along a continuum of connectivity, with a great deal of spatial heterogeneity and temporal variability, and that a lack of knowledge makes any generalization difficult. The report concludes that additional research focused on the frequency, magnitude, timing, duration, and rate of change of fluxes from GIWs to downgradient waters is needed. Here we provide a new conceptual frameworks that can be used to generate hypotheses regarding how these systems vary over space and time, with a specific focus on the effects of GIWs on flows in downgradient waters. Specifically, we conceptualize GIWs as nodes in hydrologic networks that can receive, store, and send water, and consider the network scale effects of GIWs on flow generation. The cumulative effect of many GIWs can play an important role in landscape-scale hydrology by regulating the frequency, magnitude, timing, duration, and rate of flows to downgradient waters. This cumulative effect emerges from lag, sink, and source functions resulting in time-varying flows being directed towards downgradient waters along overland, shallow subsurface, and deep groundwater flowpaths. Improving our understanding of the aggregate effects of GIWs will require (a) the development of a classification system that can be used to define regions or conditions under which GIWs have expected behaviors that can be studied in aggregate, (b) increasing emphasis on regional-scale data collection, including both field data and remote-sensing data, and (c) improving the sensitivity and accessibility of modeling and analytical tools that can be used to evaluate the aggregate effects of GIWs at the watershed scale.
