Abstract
Wetlands in the Mississippi River Valley provide numerous functions supported by prolonged periods of soil saturation or inundation. However, few studies document forested wetland hydropatterns, especially in altered systems. In this study, we evaluated hydrologic drivers of forested wetlands in the Yazoo Basin, a large Mississippi River tributary system exhibiting regional hydrologic alteration. Results from 56 water table monitoring locations indicate that precipitation induced the majority (76%) of wetland saturation events, defined as soil inundation or water tables within ≤30 cm of the surface for ≥14 consecutive days. Flooding triggered 19% of saturation events, and 5% of events occurred in response to precipitation induced high water tables followed by flood inundation. Data suggest that most wetlands examined (87%) would persist in the absence of flooding, and that duration and inundation patterns differed with dominant water source. A multi-year hydropattern analysis highlights the influence of precipitation derived saturation during low evapotranspiration winter periods, spring flood water contributions in some wetlands, and decreasing water tables throughout summer and fall. A discussion of rainfall normality and stream discharge places the dataset in a larger context. Results reflect changes in historic hydropatterns, informing efforts to maximize wetland functions during forested wetland management and restoration.
Highlights
Forested wetlands within the Mississippi River alluvial valley provide a variety of wetland functions including maintenance of faunal and floral habitats, detention and storage of precipitation and floodwater, and biogeochemical cycling of nutrients (Smith and Klimas 2002)
In response to the need for additional research, we evaluated hydrologic drivers in forested wetlands within the Yazoo Basin, a major tributary to the Mississippi River that has undergone extensive hydrologic alteration
19.6% of locations received sufficient precipitation to induce wetland hydrology, with subsequent flooding either 1) supplementing precipitation-driven hydrology (10.7%) during a continuous event (Fig. 3c) or 2) leading to a separate wetland saturation event (8.9%) following a period when water tables decreased below 30 cm for some period (Fig. 3d)
Summary
Forested wetlands within the Mississippi River alluvial valley provide a variety of wetland functions including maintenance of faunal and floral habitats, detention and storage of precipitation and floodwater, and biogeochemical cycling of nutrients (Smith and Klimas 2002) These functions result in flood risk reduction, water quality improvements, and recreational opportunities that benefit society. Spring flooding provides hydrologic supplements in some systems, and water levels decrease as the growing season progresses, evapotranspiration accelerates, and precipitation declines This classic view of forested wetland hydropattern is well established, but may not reflect current conditions since much of the Mississippi River Valley has been altered by the construction of levees, drainage works, stream channelization and dredging (Theiling and Nestler 2010). We discuss implications for forested wetland restoration and management
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