Publikationsdatum:
2014-08-20
Beschreibung:
Recent U.S. Supreme Court rulings have limited federal protections for geographically isolated wetlands (GIWs) except where a “significant nexus” to a navigable water body is demonstrated. Geographic isolation does not imply GIWs are hydrologically disconnected; indeed, wetland-groundwater interactions may yield important controls on regional hydrology. Differences in specific yield (S y ) between uplands and inundated GIWs drive differences in water level responses to precipitation and evapotranspiration, leading to frequent reversals in hydraulic gradients that cause GIWs to act as both groundwater sinks and sources. These reversals are predicted to buffer surficial aquifer dynamics and thus baseflow delivery, a process we refer to as landscape hydrologic capacitance. To test this hypothesis, we connected models of soil moisture, upland water table, and wetland stage to simulate hydrology of a low-relief landscape with GIWs, and explored the influences of total wetland area, individual wetland size, climate, and soil texture on water table and baseflow variation. Increasing total wetland area and decreasing individual wetland size substantially decreased water table and baseflow variation (e.g., reducing baseflow standard deviation by as much as 50%). GIWs also decreased the frequency of extremely high and low water tables and baseflow deliveries. For the same total wetland area, landscapes with fewer (i.e., larger) wetlands exhibited markedly lower hydrologic capacitance than those with more (i.e., smaller) wetlands, highlighting the importance of small GIWs to regional hydrology. Our results suggest that GIWs buffer dynamics of the surficial aquifer and stream baseflow, providing an indirect but significant nexus to the regional hydrologic system.
Print ISSN:
0043-1397
Digitale ISSN:
1944-7973
Thema:
Architektur, Bauingenieurwesen, Vermessung
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Geographie
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