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Watershed-scale effects of isolated wetlands on downstream hydrology: modeling approaches
Citation:
GOLDEN, H. E., H. SANDER, C. R. LANE, K. PRICE, AND E. D'Amico. Watershed-scale effects of isolated wetlands on downstream hydrology: modeling approaches. Presented at 9th INTECOL International Wetlands Conference, Wetlands in a Complex World, Orlando, FL, June 03 - 08, 2012.
Impact/Purpose:
This work provides supportive science, via hydrological modeling approaches, towards identifying a significant nexus between GIWs and downstream navigable waters.
Description:
Geographically isolated wetlands (GIWs) are depressional features on an eroding landscape that are entirely surrounded by uplands. These wetlands are purported to provide an array of ecological and watershed values and functions, including increasing biodiversity, modifying watershed biogeochemical cycling, and water storage and recharge. The 2001 Solid Waste Agency of Northern Cook County (SWQANCC) vs. the US Army Corps of Engineers ruling by the US Supreme Court limited the protection of GWIs under the Clean Water Act (CWA). The subsequent 2006 Rapanos vs. United States decision suggested that GIWs could be afforded increased CWA protection if a significant nexus between GIWs and navigable downstream waters could be identified. This ruling unveiled a key area of research for informing policy and decision-making: the development of approaches to determine whether a hydrological, chemical or biological significant nexus exists between GIWs and navigable waters. However, due to the recentness of this decision, approaches for determining whether such connections between GIWs and downstream waters remain limited. Models are critical tools for assessing the hydrologic connectivity of GIWs to surface and ground water systems and evaluating the effect of GIWs on downstream hydrologic functions. Herein we detail an empirical approach to examine whether hydrologic connectivity between isolated wetland complexes and downstream hydrology exists and how this potential connectivity may affect downstream watershed hydrology. We use simulated streamflow data from the Soil and Water Assessment Tool (SWAT) for over 500 subbasins in the Neuse River Watershed of North Carolina, USA, and an array of landscape metrics derived from spatial data sets, including those associated with GIWs, land cover, and soils. These variables are used to assess the statistical relationships between streamflow and multiple landscape parameters to determine whether those parameters associated with GIWs are related to streamflow variabilty. We provide preliminary findings from this empirical modeling approach and explore potential mechanistic modeling approaches that could assist in determining hydrological connections between GIWs and navigable waters.