Hydrology & Water
Quality
Wetlands
exist as a result of saturated soil conditions. While that notion
of wetlands is readily acknowledged, there is a poor understanding
of the hydrologic conditions that cause soil saturation for periods
prolonged enough to cause anoxia and hence limit the site to hydrophytic
species. Precipitation, ground water, or flooding are the sources
of water that can cause soil saturation. Soil properties and geomorphic
setting interact with those sources of water to yield a complex
matrix of conditions that control wetland functions.
The
most widely acknowledged hydrologic functions attributed to wetlands
include groundwater recharge, water purification, and flood control.
These functions, however, are not universal among wetland types.
In fact, the hydrologic function of a wetland may change according
to landscape position.
Important
forest resource management and conservation issues are contingent
on wetland hydrology. These issues include:
- productivity
- buffer zones
- surface and ground water quality
- habitat
- flood control
All
of the studies conducted at the Center consider hydrology as an
integral component. Specific hydrologic studies at the Center are
designed to provide the information needed for the management and
conservation of forested wetlands. The four main areas of hydrologic
research are:
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Basic
Wetland Hydrology
Research is targeted to address the hydrology of
riverine, depressional and basin wetlands. These geomorphic settings
comprise the majority of the forested wetland types. Specific studies
are targeted at understanding the source, flux and periodicity of
water in each of the settings, and to ascertain the temporal and
spatial variation in hydrologic properties. Watersheds on the Santee
Experimental Forest provide over 25 years of measurements on a lower
coastal plain forest, while work on the Coosawhatchie river provides
information on a 3rd order blackwater stream. Carolina bays, depressional
wetlands, are being studied using traditional hydrologic methods
combined with tracer studies to ascertain the flowpaths in the interface
zone between the upland and wetland.
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Hydrologic
Linkages Among Ecosystems
Movement of water among ecosystems is the factor
that links uplands, wetlands, and aquatic ecosystems. Research is
being conducted in conjunction with the restoration of the Pen Branch
system on the Savannah River Site (DOE Reservation, near Aiken,
South Carolina) to determine the flux and transformation of nutrients
and organic matter through natural and restored wetlands. The hypothesis
being tested is that early successional wetland communities affect
the quantity and composition of organic matter and nutrients entering
the adjoining stream. Similar research is being conducted on forests
of the Santee Experimental Forest watersheds, which are recovering
from blow-down of the forest by Hurricane Hugo, and on several sites
where plantations adjoin wetlands or riparian zones.
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Water
Quality
Research that focuses on water quality has two
principal facets. The first relates to hydrologic and soil processes
that affect water quality flowing through a wetland. This line of
research is fundamental to designing effective buffer zones for
ameliorating non-point runoff from adjoining uplands. The second
facet considers the interaction of land management practices and
water quality, as a basis for designing management practices that
do not degrade water quality. Research is considering the effects
of harvesting on a riverine wetland, and other studies are considering
the effects of harvesting and site preparation on basin wetlands.
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Modeling
Models are a useful tool for assessing hydrology, water quality, in-stream transport and biogeochemistry. They also provide a basis for evaluating silvicultural and water management plans, identifying information gaps, and addressing hypothetical scenarios on land use and climate change impacts. Our modelling research focuses on linking hydrologic and biogeochemical processes in managed forested landscapes. We are collaborating with North Carolina State University scientists on application of DRAINMOD-based models to forested landscapes in the southeast. DRAINMOD was originally developed for design and evaluation of agricultural drainage and related water management systems. DRAINMOD http://www.bae.ncsu.edu/soil_water/drainmod/index.html
is a field-scale, one dimensional model that simulates water and heat flow for high water table soils with artificial drainage systems. Recently, the model has been modified to describe the hydrology of pine forests, and research to extend it to predict nutrient fate and transport in the forest ecosystems is underway.
We are continuing with modelling works on pine plantations and applications to natural mixed-pine hardwood stands in the coastal plain. For example, efforts are currently underway to test a SWAT, a watershed-scale hydrology and water quality model, for predicting the hydrology of the low-gradient poorly drained forested landscape. Ongoing companion modelling studies in cooperation with University of New Hampshire and Forest Service Southern Global Change Program include linkage of DNDC (a field-scale biogeochemical model) with MIKESHE (a process-based distributed, watershed-scale hydrologic model) and DNDC with SWAT for addressing watershed-scale effects of land use change and effects of land management practices on emissions of greenhouse gases.
Forest Nutrient Cycling and Transport Modeling Workshop, March 6-7, 2008
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For more information, contact:
Dr. Devendra Amatya
phone: (843) 336-5612
e-mail: damatya@fs.fed.us
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