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The
Shale Hills Watershed is a 7.9 hectare (19.5 acre) forested site in
the Ridge and Valley Physiographic province in central Pennsylvania.
It is a first order, V-shaped basin characterized by steep slopes
(25-45%) and narrow ridges. The stream is a tributary of Shavers Creek
which eventually reaches the Juniata River and onto the Susquehanna
River. The basin is oriented in an east-west direction and the major
side slopes have almost true north and south facing aspects. Elevation
ranges from 256 m (839 ft) at the outlet to 310 m (1017 ft) at the
highest ridge. The relatively uniform side slopes are periodically
interrupted by eight distinct topographic depressions (swales).
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Shale
Hills Unit |
In
the 1970's a comprehensive hydrologic experiment was conducted on
the watershed. The study, conducted by the Forest Hydrology group
at Penn State, sought to experimentally determine the physical mechanisms
of streamflow generation at the upland forested catchment and to evaluate
the effects of antecedent soil moisture on stormflow volume and timing.
The experiment consisted of a comprehensive network of piezometers,
neutron access tubes, and 4 weirs. A spray irrigation network was
installed to apply a controllable amount of rainfall over all or part
of the entire watershed. The data collected were used for many years
for teaching and research. The robust dataset collected during that
time period is still yielding valuable information.
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In the mid-1990's
Drs. Duffy, Lynch and Cusumano, revisited the Shale Hills dataset
for the purpose of validating a dynamical model for hillslopes and
small catchments. One product of this effort was to make this data
available to the hydrologic community as a testbed for dynamic catchment
response.
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Since 2003,
the Shale Hills has seen renewed research activities from members
of the Penn State Hydropedology team, with the intent to make the
Shale Hills a long-term Hydropedologic Observatory. Out goal is to
use such a hydropedologic observatory for investigating fundamental
processes of landscape water fluxes at multiple scales, including
flow pathways, and to characterize spatio-temporal patterns of surface
and subsurface soil moisture and their relations to landscape features.
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Detailed soil
and depth to bedrock mapping have been conducted. In addition, in
cooperation with USDA-NRCS,
ground-penetrating radar (GPR) and electromagnetic induction (EMI)
methods were tested at the watershed to assess the suitability of
these techniques in mapping depth to bedrock, understanding soil variability,
and monitoring soil moisture dynamics. Starting in the summer of 2003
an intensive monitoring effort has been conducted to explore the spatial
and temporal variability of soil moisture and its relation to a number
to terrain parameters, soil types, and other landscape features. A
total of 77 multi-depth Time Domain Reflectometry (TDR) access tubes
have been installed to allow monitoring of soil moisture content at
different depths. Twelve of these sites were also instrumented with
nested tensiometers, pieziometers, thermocouples, and shallow observation
wells. Monitoring data of soil moisture at multiple depths, soil water
potential, soil temperature, shallow water table, stream discharge,
and precipitation have been collected throughout the year. Monitoring
at these sites is ongoing and intended to be long-term effort. We
are currently in the process of selecting five super sites (one for
each of the five soil series identified in the watershed) for further
instrumentation with automatic monitoring systems.
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conceptual model of hillslope hydrology has been developed for the
Shale Hills watershed that portrays typical soil moisture profiles
along the hillslope and identifies four main flow pathways downslope
(i.e., subsurface macropore flow, subsurface lateral flow at A-B horizon
interface, return flow at footslope and toeslope, and flow at the
soil-bedrock interface). Further testing of this conceptual model
would lead to enhanced understanding and modeling of preferential
flow dynamics at the small watershed scale, particularly in relation
to the role of soil distribution and lateral flow. These results shed
light on the "black box" model hydrologists often treat
soils in hillslope and watershed hydrology. This research demonstrates
the synergies of integrating pedological and hydrological expertise.
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Contact
the Researcher.
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