Tufford ASABE april 2006

1
Hydrology and water quality of seepage slope
wetlands on the SC Coastal Plain Daniel L.
TuffordDepartment of Biological Sciences,
University of South Carolina, Columbia, SC 29208
Results
Discussion Seasonal hydrology follows expected
patterns in these wells. During summer there is a
diurnal cycle in water table depth. This is
caused by evapotranspiration that increases
during early morning to a daily peak in the
afternoon. This signal is reduced by autumn
(November 3), which reflects the senescence of
many plants and overall reduction in biotic
activity. During winter (data not shown) this
signal is gone. Response to rain events is
clearly different between the two sites. The BF
hydrograph has a steep rise and steady recession,
typical of headwater streams. In this case the
rise is caused by precipitation in the immediate
vicinity of the well, while the recession curve
and duration indicates lateral flow from the
upland. At the WNP well both the rise and initial
recession are steep. There appears to be a
secondary hydrograph when additional water
reaches the well. This secondary flow is
substantial and is capable of displacing the
timing of the diurnal peak. The differences
between the two sites are probably the result of
different upland topography. The WNP site has
much higher bluffs (Table 1), which increases
travel time within the soil layer. There are
seasonal differences in water quality as well as
differences between wells at each site. The water
tends to be much lower in DO concentration during
the summer (July 27) than other seasons in all
wells, with differences within site as well. The
within-site differences persist in the autumn
although concentrations increase. By winter the
concentrations are relatively the same. Similar
comments apply to redox potential. DOC appears
to decrease from summer into winter. This is
consistent with less microbial activity as
temperatures moderate. For both nitrogen and
phosphorus (not shown) the organic fraction is
substantially larger than the inorganic fraction.
The seasonal pattern of TN appears to be
different between wells at the same site. This
could be another manifestation of differences
seen in the DO and redox potential. Additional
investigation is needed.
Wells, instrumentation, and sampling A shallow
well was placed adjacent to each seep. The wells
(Figs. 2 and 3) were constructed following the
guidelines from Sprecher (1993) as modified by
Sprecher (2000). The wells range from 1.2 to 1.4
m deep. Each well has a Global WL15 water level
recorder with a 1 hour recording interval. The
wells were purged with a bailer several times in
the weeks immediately following installation. An
Onset tipping bucket recording rain gauge was
deployed in a nearby location with no canopy.
Once installed and stable the wells were
visited seasonally to retrieve water level data,
take water quality field parameter measurements
with a YSI 600XLM sonde, and collect water
samples for laboratory analysis. The wells were
purged prior to taking YSI measurements and
collecting water for analysis. The water was
analyzed for nitrogen and phosphorus fractions
and dissolved organic carbon (DOC) at an SCDHEC
certified commercial laboratory.
Introduction Seepage wetlands occur at the base
of slopes and bluffs, typically at the outer edge
of a floodplain or stream corridor. Unlike
riverine wetlands, however, these receive most of
their water from seeps and springs that discharge
groundwater flow from adjacent upslope land.
Seepage wetlands are relatively common on the
Southeastern Coastal Plain in fact they are a
dominant feature on many of the landscapes in
which they occur. It is believed they serve
important roles in local and regional
biodiversity, water quality, and biogeochemical
cycling. These conclusions are based on a small
amount of field data and inference from other
wetlands on the coastal plain. It is likely that
because the surrounding uplands are the primary
source of water, these habitats are especially
vulnerable to the effects of nearby land
management activities. The nature and extent of
the vulnerability is unknown. This poster
provides preliminary results from one component
of a broader project to begin a descriptive and
systems ecological study of seepage wetlands on
the South Carolina Coastal Plain.
Fig 4. Precipitation and water table depth at one
well in Beidler Forest during summer and autumn
2005.
Fig 5. Precipitation and water table depth at one
well in Wannamaker Nature Preserve during summer
and autumn 2005.
Fig. 2. Monitoring well profile from Sprecher
(1993). The wells in this project did not include
the grout layer or well point, as suggested in
Sprecher (2000).
Study sites For the initial study we selected
two seeps at each of two sites (Fig. 1 Table 1).
The objective was to facilitate assessment of
variability both within a site and among sites.
One site is owned by National Audubon Society
the other by Charleston Natural History Society,
a local chapter of the national organization.
The Beidler Forest (BF) site is old-growth
cypress-tupelo swamp, although the upland
adjacent to the study seeps is second- or
third-growth mixed hardwood. The Wannamaker
Nature Preserve (WNP) site is second- or
third-growth mature bottomland hardwood on the
floodplain and mature upland hardwood upslope
from the seeps. The Preserve encompasses a
working farm that has been out of production for
15-20 years.
Fig. 6. Seasonal dissolved organic carbon
concentrations in the four wells.
Literature cited Sprecher, S. W. 1993. Installing
Monitoring Wells/Piezometers in Wetlands. WRP
Technical Note HY-IA-3.1, US Army Corps of
Engineers, Waterways Experiment Station,
Vicksburg, MS. Sprecher, S. W. 2000. Installing
Monitoring Wells/Piezometers in Wetlands. ERDC
TN-WRAP-00-02, US Army Research and Development
Center, Vicksburg, MS.
Fig. 7. Seasonal ammonia concentrations in the
four wells.
Fig. 1. Two seeps are located at Francis Beidler
Forest (1, Dorchester County, Four Holes Swamp
watershed) and two are at Wannamaker Nature
Preserve (2, Calhoun County, Halfway Swamp Creek
watershed).
Acknowledgments This work was funded by Audubon
South Carolina and The Nature Conservancy.
Special thanks go to Norman Brunswig, John
Nelson, Steve Bennett, Kristin Harrison, and Dick
Watkins.
Fig. 8. Seasonal total nitrogen concentrations in
the four wells.
Table 1. Physical descriptions for the two study
sites. At each site the wells are in seeps that
are approximately 75 m apart. (TBD to be
determined)
For further information Please contact Dan
Tufford (phone [phone] e-mail
tufford_at_sc.edu) for more information.
Fig. 3. One of the wells in Beidler Forest.